https://doi.org/10.14940/netsushori.62.95

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https://doi.org/10.2320/matertrans.MT-M2021241

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https://doi.org/10.2464/jilm.72.265

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https://doi.org/10.2320/matertrans.MT-M2021213

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https:// doi.org/10.3390/jmmp6020029

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https://doi.org/10.1016/j.apsadv.2021.100129

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https://doi.org/10.14940/netsushori.61.183

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https://doi.org/10.2320/matertrans.MT-M2020387

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https://doi.org/10.2320/jinstmet.J2020060

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https://doi.org/10.4028/www.scientific.net/DDF.405.3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

High-entropy alloys (HEAs) were fabricated by powder metallurgy using gas-atomized powder and spark plasma sintering (SPS) followed by surface modification (plasma nitriding) of the sintered sample. Plasma nitriding forms nitride and induces solid-soluting of N; it enables the diffusion of N atoms by removing the passive film formed on the surface of alloys such as stainless steel, Al alloys, and Ti alloys, via the sputtering of cations during glow discharge. Therefore, plasma nitriding has the potential to process HEAs that contain strong oxidizing elements such as Cr, Al, and Ti. In this work, a sintered CoCrFeMnNi HEA was plasma-nitrided and its properties were subsequently evaluated. A uniform microstructure without segregation was obtained in the SPS sample, and its hardness and wear resistance were found to have improved. Analysis of the sample surface after nitriding revealed that an expanded face-centered cubic phase formed on the surface plasma-nitrided at 673 K and that a CrN phase formed on the surface plasma-nitrided at temperatures greater than 723 K. The surface hardness of the plasma-nitrided sample was 1200 HV or greater, and the wear resistance and pitting corrosion resistance were improved compared with those of the untreated sample.

DOI： 10.3390/met10060761

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http://doi.org/10.35840/2631-5076/9248

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

Low carbon steel sample S15C was nitrided by active screen plasma nitriding (ASPN) and direct current plasma nitriding with screen (S-DCPN) using a chromium screen to form simultaneously chromium nitride coating/nitrogen-diffusion layer on the sample surface. The sample was placed on the sample stage in a floating potential and a cathodic potential. A chromium screen was mounted on the cathodic stage parallel to the top of the sample. Plasma nitriding treatments in a floating potential (ASPN) and a cathodic potential (S-DCPN) were performed in a nitrogen-hydrogen atmosphere with 75% N-2-25% H-2 for 120 min at 773K and 873K under 200 Pa. After nitriding, the nitrided microstructure was examined with a scanning electron microscope, glow discharge optical emission spectroscopy and X-ray diffraction studies. In addition, the hardness and corrosion properties were also measured. The nitrided layer formed by S-DCPN consisted of a Cr-concentrated layer (similar to 750 HV) followed by a nitrogen-diffusion layer whereas that formed by ASPN consisted of deposited layer of chromium nitrides and iron nitrides without nitrogen-diffusion layer. Corrosion resistance of the samples treated by S-DCPN was better than that of untreated sample and sample treated by ASPN.

DOI： 10.2320/matertrans.H-M2020815

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Plasma nitriding is used for materials that are challenging to nitride by conventional techniques. Because of the sputtering effect of positive ions during glow discharge, protective oxide films on the surfaces of materials including stainless steels, aluminum alloys, and titanium alloys, can be effectively removed by ion and energetic particle bombardment; thus, nitrogen mass transfer from the plasma into the component subsurface can be achieved effectively. Plasma nitriding therefore has potential applicability to treat high-entropy alloys (HEAs) containing large amounts of strong oxide-forming elements such as chromium. In this study, the effects of plasma nitriding were investigated on the microstructural, mechanical, and corrosion properties of a CoCrFeMnNi HEA with an fcc structure that is soft and ductile. The HEA was produced by melting pure metals and casting. Direct-current plasma nitriding was then performed in a gas mixture of 25% N-2 and 75% H-2 for 54 ks at 673-823 K under 200 Pa with an auxiliary cathodic screen. After nitriding, the nitrided samples were examined using scanning electron microscopy, X-ray diffraction (XRD), Vickers microhardness testing, electron probe micro-analysis, and glow discharge optical emission spectroscopy (GD-OES). After nitriding, GD-OES revealed that the thickness of the nitriding layer tended to increase with increasing nitriding temperature. XRD analysis revealed that an fcc supersaturated solid solution phase was formed on surfaces nitrided below 723 K, whereas a CrN phase was formed on those nitrided above 723 K. The Vickers microhardness of the nitrided sample surfaces reached approximately 1300 HV. Ball-on-disk wear tests revealed that the wear loss of nitrided samples was considerably lower than that for untreated samples. Finally, the pitting corrosion resistance of samples nitrided at 673 K was higher than that of untreated samples.

DOI： 10.1016/j.surfcoat.2018.06.088

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https://doi.org/10.11283/jlwa.57.198

DOI： 10.11283/jlwa.57.198

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

This study focused on a diffusion coating method for the formation of a hard layer with excellent adhesion through the formation of an interlayer and a gradient layer on titanium materials. A limitation of conventional diffusion coating methods is the deterioration of the mechanical properties of the matrix resulting from the long-term, high-temperature processing. Therefore, spark plasma sintering (SPS) was used to form a ceramic layer, as it allows the suppression of the growth of crystal grains via rapid heating and enables low temperature and short processing time. The purpose of this study is to simultaneously form borides and carbides on a titanium surface using the SPS method and evaluate their properties. Commercially pure titanium (CP-Ti) was used as the substrate, and B4C powder was utilized as both the boronizing and carburizing source. An analysis of the sample surface subjected to SPS processing indicated the formation of TiC, TiB2, and TiB. As a ceramic layer was formed on the titanium surface, a surface hardness of similar to 1700HV was obtained, and the wear resistance was improved compared with that of untreated CP-Ti.

DOI： 10.2320/matertrans.L-M2019838

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

Aluminum alloys are light and have good workability; however, their low hardness and poor wear resistance are drawbacks limiting their wide application in the automotive industry. The deposition of diamond-like carbon (DLC) films, which exhibit high hardness and good wear resistance, onto the surface of Al alloy substrates, can overcome these drawbacks. As Al alloys and DLC films have low affinity for each other. adhesion between the two is poor; adhesion can be improved by using of an interlayer. For coatings with the same thickness, film properties are improved by forming multilayer structures. In this study, the sample was formed with a uniform film thickness of 2 mu m, to change the thickness ratio of the Si DLC/DLC layer to 1:1 or 1:3 and to change the number of multilayers [Si -DLC/DLC](N) to 1, 2, and 4. The samples were then tested by nanoindentation, Rockwell indentation, scratch, and wear tests. The sample with a thickness ratio of 1:1 increased the hardness and hardness/Young's modulus (H/E) of the film by increasing the number of multilayers repetitions. However, for the sample with a thickness ratio of 1:3. 2 and 4 multilayer repetitions did not effect a significant difference in the hardness and H/E ratio. These samples did not improve the adhesion properties, because of no significant difference by the Rockwell indentation and scratch tests. By the wear test, samples with a 1:1 thickness ratio of the multilayer increased the delamination length and decreased the friction coefficient with increasing number of multilayers repetitions. Samples with a 1:3 thickness ratio of the multilayer increased the delamination length with increasing number of multilayers repetitions, whereas samples with 2 and 4 multilayers did not cause a significant difference in the delamination length. Moreover. the friction coefficient of the samples decreased with increasing number of multilayers repetitions. This study showed the delamination length of DLC films is proportional to increasing H/F. ratio.

DOI： 10.2320/jinstmet.J2018060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Aluminum (Al) alloys are light and have good workability; however their low hardness and poor wear resistance are drawbacks limiting their wide application in the automotive industry. Deposition of diamond-like carbon (DLC) films, which exhibit high hardness and good wear resistance, onto the surface of Al alloy substrates can overcome these drawbacks. Because Al alloys and DLC films have low affinity for each other, adhesion between the two is poor. However, the use of an interlayer can improve adhesion. To investigate the effect of multiinterlayers on the adhesion and durability of DLC films on Al substrates, DLC films with Ti, Si-DLC, or Ti/Si-DLC interlayers were deposited onto A2024 substrates using plasma-enhanced chemical vapor deposition (PECVD). Prior to PECVD, an Ar-bombardment treatment was conducted to clean the surface of the substrate. Subsequently, a Ti interlayer was deposited by sputtering for 15 min, a Si-DLC interlayer was deposited using a tetramethylsilane (TMS) and methane gas mixture for 15 min, and DLC was deposited using methane gas for 90 min. The nanohardness of the Ti/Si-DLC multi-interlayered sample reached 33 GPa more than 8 GPa higher than that of the single-interlayered samples. In addition, the Ti/Si-DLC multi-interlayered sample exhibited higher hardness/Young's modulus (H/E) ratios than the single-interlayered samples. Wear tests showed that the wear volumes for the balls and the multi-interlayered samples were smaller than those for the single-interlayered samples. In addition, the delamination distance of the Ti/Si-DLC multi-interlayer sample was 3300 m, more than 1500 m longer than that of single-interlayered samples. This study demonstrates that improving the wear resistance required high plastic index parameter (H/E) values rather than high H values.

DOI： 10.1016/j.surfcoat.2018.08.094

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Titanium materials are widely used in aerospace, automotive and biomaterial engineering fields due to high specific strength, superior fatigue and corrosion resistance as well as excellent biocompatibility. However, titanium exhibits low hardness and poor wear resistance. Therefore, the development of a suitable surface modification technology is necessary to expand the use of titanium materials. In order to improve hardness and wear resistance of materials, there is the method to form the hard ceramics layer on the matrix surface. In this study, carburizing method was applied. The carburizing method can form the carbide layer which is superior in adhesion with the matrix compared with PVD or CVD method. However, in conventional carburizing methods, the deterioration of the mechanical properties of the matrix as a result of long-term and high-temperature processing is problematic. Therefore, spark plasma sintering technique, which features short processing times, was applied to form a carbide layer in this study. The purpose of this research is to form a TiC layer on commercially pure Ti (CP-Ti) and evaluate its properties. CP-Ti was used as the substrate, and graphite powder was used as the carburizing source. XRD analyses indicated that a TiC layer was formed on the substrates. Corrosion tests indicated that the corrosion resistance of the carburized samples was remarkably improved compared to that of CP-Ti. Wear tests revealed that the carburized samples exhibited low friction coefficients and improved tribological properties.

DOI： 10.1016/j.surfcoat.2018.08.092

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DOI： 10.2472/jsms.67.715

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Language：Japanese   Publishing type：Research paper (other academic)  

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：アグネ技術センター  

CiNii Books

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

The low hardness and poor tribological performance of titanium alloys restrict their wide applications in automotive fields. Nitriding is widely used to improve tribological properties, wear resistance, and corrosion resistance of steel and titanium alloys. Plasma nitriding is becoming increasingly popular because of its high nitrogen potential, short treatment time, and low environmental impact. Recently, considerable interest has been devoted to alternative nitriding methods such as active screen plasma nitriding (ASPN). In this study, a Ti-6Al-4V titanium alloy was nitrided by ASPN using a titanium double screen in order to investigate the effect of applying the double screen on the microstructure of the nitriding layer. The Ti-6Al-4V sample was placed on the sample stage in a cathodic potential. A titanium double screen was mounted on the cathodic stage around the sample stage. The sample was treated for 1-25 hours at 600ºC under 200 Pa in 75% N2 + 25% H2 atmosphere. After nitriding, glow discharge optical emission spectroscopy (GD-OES) revealed that the thickness of the nitriding layer composed of TiN tended to increase with increasing the nitriding time. The Vickers microhardness of the sample surface nitrided for 25 hours reached approximately 1300 HV0.01. Ball-on-disk wear test revealed that a wear loss of nitrided sample considerably decreased than that of untreated sample.

DOI： 10.4028/www.scientific.net/MSF.891.11

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：UNIV FED SAO CARLOS, DEPT ENGENHARIA MATERIALS  

This research used the "cathodic cage (CC)" technique for TiO2 film deposition on duplex stainless steel substrate. This technique uses a multiple hollow cathode effect. Duplex stainless steel substrates were treated at temperatures of 300 degrees C, 350 degrees C and 400 degrees C, giving a temperature value ratio (T-s/T-m) of 0.27 to 0.31 (Ts being the substrate temperature and Tm the melting temperature of the deposited material). Treatment times of 1, 2 and 4 hours were administered and polycrystalline TiO2 films were obtained. The films were analyzed by optical microscopy (OM), X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). During analysis, the formation of uniform films and the possibility of controlling the TiO2 phase were observed. It was also shown that with longer treatment times and higher temperatures the rutile phase predominates. For treatment times of 4 hours at all temperatures, the rutile structure was present. With treatment times of less than 4 hours, anatase was present. In addition, results showed that this simple, low cost technique can be an alternative method for depositions of TiO2 films, with the advantage of high levels of control over porosity, thickness and phase composition (anatase and rutile).

DOI： 10.1590/1980-5373-MR-2015-0358

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

The S-phases (γN-phases) of SUS304 steel were prepared using direct current plasma nitriding (DCPN) and active screen plasma nitriding (ASPN). Furthermore, diamond-like carbon (DLC) films on these S-phases were prepared using plasma chemical vapor deposition (PCVD). The nitride layers included the γ'Fe4N phase. The Xray stress constant K of the nitride layers were evaluated using γN (200)+γ'Fe4N(200) diffraction with CrKa characteristic X-rays. The γN (200)+γ'Fe4N(200) diffraction angle 2θ of DCPN powder and ASPN powder were 73.49° and 72.98°, respectively. The X-ray stress constants of the γN (200)+γ'Fe4N(200) phase nitrided using DCPN and ASPN, E / (1+v ) , were 202 GPa and 153 GPa, respectively. The X-ray stress constant K of the γN (200)+γ'Fe4N(200) phase nitrided using DCPN and ASPN were -2,365 MPa/deg and -1,809 MPa/deg, respectively. The X-ray residual stress of these S-phases prepared using DCPN and ASPN were approximately -5.3 GPa and -2.6 GPa, respectively. On the other hand, Raman microprobe spectroscopy was used for residual stress measurements of the DLC films deposited on these S-phases. The Raman spectra of the DLC films were classified into the disorder (D') peak at 1,150 cm-1, D peak, and graphite (G) peak. The residual stresses in the DLC films on these S-phases as estimated from the Raman shift of the G peak for DCPN and ASPN were -3.2 GPa and -3.0 GPa, respectively. The hardness of the DLC films as determined using the nano-indentation method was very large. It is possible that increases in compressive residual stresses in the DLC films caused decreases in the contact areas and the indentation depth of the indenter, which appeared to cause increases in the Young's modulus and hardness of the DLC films.

DOI： 10.2472/jsms.65.517

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Austenitic stainless steel SUS 316L was nitrided by active-screen plasma nitriding (ASPN) to investigate the effect of surface deposits from the screen on the nitriding layer formation. ASPN experiments were carried out using a DC plasma-nitriding unit. The sample was placed on the sample stage in a floating potential (bias-off) and a cathodic potential (bias-on). The screen, which was SUS 316L expanded metal with 38% open area ratio, was mounted on the cathodic stage around the sample stage. Nitriding was performed in a nitrogen-hydrogen atmosphere with 25% N-2 + 75% H-2 for 18-180 ks at 673 K under 200 Pa by the ASPN process. After nitriding, the nitrided samples were examined using scanning electron microscopy, X-ray diffraction, Vickers microhardness and glow discharge optical emission spectroscopy. From the surface observation of the nitrided sample, deposits were observed on the top surface of the sample nitrided with bias-off whereas deposits were not on that nitrided with bias-on. The nitrogen-expanded austenite (S phase) was formed on the surface of both samples. Layer thickness of the S phase increased with increasing the nitriding time. Additionally, the degree of an increase of the layer thickness of the S phase nitrided with bias-on was approximately 2.5 times greater than that nitrided with bias-off. This result suggests that the ASPN treatment with bias-on is effective for the increase of the nitriding layer thickness.

DOI： 10.2320/matertrans.M2016209

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASTM International  

The nitriding process is widely used to improve the tribological properties and wear resistance of metal surfaces. An "edge effect" occurs due to distortions of the electric field around the corners and edges of the components, although the components are well heated. This results in nonuniformity in properties such as the hardness and thickness of the surface layer. Recently, there has been considerable interest in active screen plasma nitriding (ASPN). In this process, the edge effect is completely eliminated because the plasma is produced on the cage and not directly on the samples, and sputtering of material from screen is important for ASPN. In this study, austenitic stainless steel AISI 316L and silicon (Si) were nitrided by ASPN to investigate the effect of surface deposits from the screen. ASPN experiments were carried out using a DC plasma-nitriding unit. The sample was placed on the sample stage in a floating potential and isolated from the cathodic screen and the anode. The screen, which was AISI 316L expanded metal with 38 % open area ratio, was mounted on the cathodic stage around the sample stage. ASPN was performed in 25 % N2+75 % H2 atmosphere for 7.2-90 ks at 673 K under 200 Pa. After nitriding, the nitrided samples were examined using scanning electron microscopy, X-ray diffraction, Vickers microhardness, and glow discharge optical emission spectroscopy. The nitrogen-expanded austenite (S phase) was formed on the surface of both samples. Additionally, γ′-Fe4N and CrN were also formed on the Si surface. The thickness of the surface deposited layer increased linearly with increasing nitriding time. That of the nitriding layer of S phase also increased, whereas the deviation from parabolic law was observed. This result suggested that the surface deposited layer suppressed the formation of a nitriding layer.

DOI： 10.1520/MPC20150052

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Diamond-like carbon (DLC) films were prepared and their residual stresses were measured nondestructively using Raman microprobe spectroscopy. The plasma-based ion implantation and deposition (PBIID) method was used to coat the DLC films on thin glass substrates using acetylene, a mixture of acetylene and toluene, or only toluene gas at 1.0 Pa. Peaks in the Raman spectra of the DLC films were assigned as the D'(disordered) or C-C bonding peaks at 1150 cm(-1). The phonon deformation potentials (a') of the films were estimated from data for the phonon deformation potentials for pure graphite and diamond and calculated using the sp(3)/sp(2) bonding ratio and the hydrogen content of the films. Thus, a relation was observed between the Raman shift of the G peak (omega(G)) and the residual stress (sigma(c)) in each film. The Raman shifts (omega(0)) of the G peak for the films with no deformation were 1554, 1556, and 1562 cm(-1) for the films deposited using acetylene, a mixture gas and toluene gas. Moreover, only toluene had stress constants of -0.378, -0.384, and -0.391 GPa/cm(-1). The residual stresses constant in each film using (8.2 x 10(-4).a')(-1) omega(-1)(0) were estimated as -0.379, -0.384, and -0.391 GPa/cm(-1). The Raman shift of the D peak remained stationary as the compressive sigma(c) in the films increased but changed when the deposition gas was varied. The distance the D peak moved from 1420 cm(-1) corresponded to that of the G peak from 1560 cm(-1) in the Raman spectra of the films in the stress-free state. In addition, the compressive residual stress in the DLC film had a major impact on the hardness. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2015.10.048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

It has been investigated that the tiny amount of bound water in anodic oxide film on Al was quantitatively measured by thermal gas desorption spectroscopy (TDS) and correlation between the amount of bound water in the film and stability of the film was discussed. Al wire specimens were anodically polarized at 20.5 V in sulfuric acid solution to prepare the anodic oxide film on the specimen. The specimen with the film was then subjected to the film-modification process in which an anodic potential from 1.0 to 2.0 V-Ag/AgCl was applied to the specimen for 180 s in chloride solution. The specimens for which pitting corrosion did not occur were subjected to the four tests; measurements of thickness of barrier layer in the film, pitting potential, the amount of bound water in the film by the TDS and the amount of water in the porous layer by grow discharge optical emission spectroscopy (GD-OES). As a result, the thickness of the anodic oxide film formed on Al at 20.5 V was about 25 gm and independent of the modification potential. The amount of bound water was quantitatively detected by the TDS, and increased with a rise in the modification potential. However, depth profile of hydrogen, which is considered to correspond to water, in the porous layer of the film detected by the GD-OES was independent of the modification potential. The findings suggested that the bound water is included in the barrier layer. The pitting potential exhibited the maximum value when a modification potential of about 1.5 V-Ag/AgCl was applied to the specimen. According to the correlation between the amount of bound water in the film and the pitting potential, the pitting potential rose with an increase in the amount of bound water in smaller amount range, and the amount beyond the small range induces the pitting potential higher. The evidence suggests that control of the amount of bound water is key factor for improving stability of the anodic oxide film on Al.

DOI： 10.2320/matertrans.L-M2015831

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We have tried to detect the bound water in the passive film sensitively using thermal desorption gas spectroscopy (TDS) equipped with a quadrupole mass spectrometer and investigated the effect of bound water on stability of the passive film formed on Ti. Ti was electrochemically passivated in a dilute sulfuric acid solution for several periods. The passivated specimens were subjected to two methods for evaluating properties of the passive film: One was the TDS method to determine an amount of bound water in the film, and the other was a conventional electrochemical potentiokinetic method in a sodium bromide solution to determine a pitting potential corresponding to stability of the film. As a result, the TDS successfully and quantitatively detected three states of bound water from the passive film on Ti. As a passivation time increased, a pitting potential of Ti shifted to more positive direction and an amount of bound water increased. In other words, improvement to stability of the passive film was achieved by increasing the amount of bound water in the film. The finding was the opposite result from stainless steels.

DOI： 10.1007/s10008-015-3037-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：A V S AMER INST PHYSICS  

Cathodic cage plasma deposition (CCPD) was used for growing titanium nitride (TiN) and titanium dioxide (TiO2) thin films on silicon substrates. The main advantages of the CCPD technique are the uniformity, tridimensionality, and high rate of the film deposition that occurs at higher pressures, lower temperatures, and lower treatment times than those used in conventional nitriding treatments. In this work, the influence of the temperature and gas atmosphere upon the characteristics of the deposited films was investigated. The TiN and TiO2 thin films were characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy to analyze their chemical, structural, and morphological characteristics, and the combination of these results indicates that the low-cost CCPD technique can be used to produce even and highly crystalline TiN and TiO2 films. (C) 2015 American Vacuum Society.

DOI： 10.1116/1.4919770

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Language：Japanese  

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Other Link： http://hdl.handle.net/10112/10559

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Austenitic stainless steel SUS 316L was nitrided by active screen plasma nitriding (ASPN) using screens with various open areas to investigate the effect of the screen's open area ratio on the nitriding response. The sample was placed on the sample stage in a floating potential and isolated from the cathodic screen and anode. The screen, which was SUS 316L expanded metal mesh with 38%, 48%, or 63% open area ratio, was mounted on the cathodic stage around the sample stage. Nitriding was performed in a nitrogen hydrogen atmosphere with 25% N-2 + 75% H-2 for 18 ks at 693 K under 600 Pa by the ASPN process. After nitriding, the nitrided microstructure was examined using a scanning electron microscope and an electron probe microanalyzer. The phase structures on the nitrided surface were determined by X-ray diffraction. In addition, the surface hardness and cross section of the nitrided samples were measured by the use of a Vickers microhardness tester. The thickness of the nitrided layer of the S-phase decreased with increasing open area ratio of the screen.

DOI： 10.2355/isijinternational.54.916

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Pulsed electric-current sintering was applied to the bonding of tungsten to titanium. The influence of bonding condition on the bond strength of joint was investigated by observing the microstructure. The bonding process was carried out at bonding temperature from 773 to 1273 K for 1.8 ks at a bonding pressure of 40 MPa. The bond strength of the joint bonded at the temperature higher than 1173 K was around 200 MPa. This joint fractured in the tungsten during tensile test. SEM-EDX observation revealed that W diffused into Ti at the joint interface of the joint bonded at the temperature higher than 973 K.

DOI： 10.4028/www.scientific.net/MSF.782.445

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Nitriding steel sample SACM645 was nitrided by active screen plasma nitriding using a titanium double screen to form simultaneously TiN coatings/nitrogen-diffusion layer on the sample surface. The sample was placed on the sample mount of the various materials (SACM 645, Cu, Ti and SiO2-Al2O3). The sample with the mount was placed on the sample stage in a cathodic potential. A titanium double screen was placed on the cathodic stage around the mount. Active screen plasma duplex processing were performed in 75% N-2 + 25% H(2)atmosphere for 18 ks at 823 K under 100 Pa. In each sample, the hardness of the sample surface was high and beneath compound layer, the hardness decreased rapidly with the distance from the surface, following a flattening of the profile. Wear loss of each duplex-processed sample decreased than that of untreated sample. Particularly, wear loss of the sample using the Ti mount considerably decreased.

DOI： 10.4028/www.scientific.net/MSF.782.16

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Language：Japanese   Publisher：The Vacuum Society of Japan  

Recent developments in plasma nitriding heat treatment technology were reviewed. The feature of plasma nitriding technology was introduced. Moreover, characteristics of the S phase, which was formed at 673 to 723 K in plasma nitriding of austenitic stainless steel, were explained. Finally, a new nitriding technology, — active screen plasma nitriding technology, was also explained.<br>

DOI： 10.3131/jvsj2.56.303

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Other Link： https://jlc.jst.go.jp/DN/JALC/10022633117?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Nitriding steel sample SACM 645 was nitrided by active screen plasma nitriding (ASPN) using a titanium screen to form simultaneously TiN coating/nitrogen-diffusion layer on the sample surface. ASPN experiments were carried out using a DC plasma-nitriding unit. The sample was placed on the sample stage in a floating potential and a cathodic potential. A titanium double screen was mounted on the cathodic stage around the sample stage. ASPN treatments at 0%-bias and 100%-bias were performed in a nitrogen-hydrogen atmosphere with 75% N-2 + 25% H-2 for 0-54 ks at 873 K under 100 Pa. After nitriding, the nitrided microstructure was examined with a scanning electron microscope, glow discharge optical emission spectroscopy and X-ray diffraction studies. In addition, the hardness of the surface and the cross-sections of the nitrided sample were measured using a Vickers microhardness tester under a 0.1-N load. The thickness of the TiN layer grew linearly with increasing nitriding time. In this case, the deposition rate of the TiN layer was 0.22 mu m/h. The nitrided layer formed by ASPN at 100%-bias consisted of a TiN compound layer followed by a nitrogen-diffusion layer. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2012.04.021

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS & MATERIALS  

To apply carbonized organics to solid-carburizing compounds, a low carbon steel, S15C substrate, was solid-carburized at 1223 K for 18.0 ks in air with various carbonized organics in nitrogen atmosphere. Each organic changed to the black carbonized matter after carbonizing at 723 K, whereas almost organics kept a shape during carbonizing. X-ray diffraction (XRD) results show that Ca-5(PO4)(3)(OH), both KCl and KHCO3, BaCO3 and CaCO3 were identified on the surface of carbonized meat and bone meal which is organic animal products, carbonized potato, pumpkin and eggplant which are organic plant products, commercial solid-carburizing powder and milled egg shell powder, respectively. As a result of cross-sectional morphology, the martensitic structure was clearly observed on the surface region of each solid-carburized S15C sample after quenching. Hardened layer depth of most samples solid-carburized with various carbonized organics were comparable to the sample treated with commercial solid-carburizing powder, or more. These results indicate that the carbonate in solid-carburizing compounds acts as energizer for solid-carburizing process and carbonized organics and milled egg shell powder can also be used as compounds and energizer for solid-carburizing process, respectively.

DOI： 10.2320/jinstmet.77.153

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The simultaneous deposition of chromium and silicon on stainless steel using a halide-activated diffusion coating process was performed to improve oxidation properties at high temperatures. Conventional procedure in diffusion coating process uses an activator containing fluoride. Fluoride is harmful for the human body and the environment. This experimental object is a development of the fluoride-free activator in diffusion coating of chromizing-siliconizing. In this investigation, Cr-Si intermetallic compound layers were coated on stainless steel by the pack cementation to improve its oxidation resistance and the resulting properties of the obtained coatings were investigated. The pack powders used for the diffusion coating were Cr and Si as diffusion element, Al2O3 as filler, and NH4Cl and CaCl2 as fluoride-free activator or NH4Cl, NaF and AlF3 as fluoride-added activator. The diffusion coating treatment was conducted at 1323 K for 18.0 ks in an Ar atmosphere. After the simultaneous deposition of chromium and silicon on stainless steel, a modified layer was observed on the treated sample surface and fluoride-free activator could also modify the steel surface using pack cementation.

DOI： 10.2320/jinstmet.J2013023

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In this study, a duplex chromizing-siliconizing coating was produced on heat-resistant austenitic stainless steel by pack cementation. The chromizing-siliconizing of the duplex chromosiliconized coating was evaluated in 873 K hot steam for 3.6 x 10(3) ks, and the oxidized as well as the coated samples were characterized. A duplex chromosiliconizing coating has been successfully applied to heat-resistant austenitic stainless steel by pack cementation. This coating containing Cr and Si can effectively improve the oxidation resistance of heat-resistant austenitic stainless steel in 873 K hot steam for 3.6 x 10(3) ks. [doi:10.2320/matertrans.M2011396]

DOI： 10.2320/matertrans.M2011396

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Language：English   Publisher：Kansai University  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Plasma nitriding is a surface modification process with a low environmental impact. Active screen plasma nitriding (ASPN) is one of the new plasma nitriding technologies, and can eliminate problems related to conventional direct current plasma nitriding (DCPN). In this study, ferritic stainless steel SUS430 samples were treated by ASPN to increase their wear resistance without decreasing their corrosion resistance. ASPN was performed in a nitrogen-hydrogen atmosphere with 25% N-2 + 75% H-2 for 18 ks at 623 K, 673 K, 723 K, 773 K, and 823 K under 600 Pa using an SUS304 screen. When the sample was treated at 673 K by ASPN, the pitting corrosion resistance and wear resistance of its surface were improved because of the formation of the S-alpha phase and a deposited layer containing Ni on the sample surface.

DOI： 10.1088/1742-6596/379/1/012052

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Cr Si intermetallic compound coatings were coated on an austenitic stainless steel SUS310S substrate by pulsed electric current sintering process to improve its wear and oxidation resistances. The coating was carried out for 0.6-10.8 ks at 1073-1323 K at a coating pressure of 60 MPa. As a result of pin on disk wear test, the wear property of the coatings was more excellent than that of the substrate. The tensile strength of the coatings was 10-20 MPa. These coatings fractured at the interface between the coatings and the substrate during tensile test. As a result of hot hardness test, the coatings showed higher hardness than the substrate, even at high temperature. Hardness of the coatings fell gradually up to the transition temperature of 870 K and decreased rapidly on further heating. As a result of oxidation testing for 700 ks at 1123 K, the mass increase of the coatings after oxidizing was less than that of the substrate. These results indicate that wear resistance and strength at elevated temperature could be given to the substrate without deteriorating oxidation resistance.

DOI： 10.2320/jinstmet.75.469

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An austenitic stainless steel AISI 304 was active screen plasma nitrided using a 304 steel screen to investigate the effect of the gas pressure on the nitriding response. The sample was treated for 18 ks at 723 K in 25 % N2 + 75 % H2. The gas pressure was changed to 100, 600, and 1200 Pa. The distance between the screen and the sample was also changed to 10, 30, and 50 mm. The nitrided samples were characterized by observing their appearance and surface roughness by optical microscopy, X-ray diffraction, and microhardness testing. After nitriding, polygonal particles with a normal distribution were observed at the center and edges of all the nitrided sample surfaces. The particles on the sample surface became finer with an increase in the gas pressure. The nitrided layer with a greater and homogeneous thickness was obtained at a low gas pressure of 100 Pa. Copyright © 2011 by ASTM International.

DOI： 10.1520/JAI103286

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The duplex stainless steel has high strength and excellent corrosion resistance. Since this steel has low hardness and wear resistance, the surface hardening treatment should be carried out under the wear environment. In this study, plasma nitriding has been applied for the improvement of wear resistance. However, traditional plasma nitriding at temperatures ranging from 723 to 823 K decreases the corrosion resistance of stainless steel. This is because the chromium in the steel reacts with nitrogen to form chromium nitride, and this decreases the concentration of chromium in the matrix, which is required for the formation of stable passive layers. Plasma nitriding carried out below 723 K forms a nitrided layer that is called the S phase. This phase improves the surface hardness without decreasing the corrosion resistance. Therefore, a low temperature plasma nitriding technique was used for treating stainless steel. Active screen plasma nitriding (ASPN) was carried out as the plasma nitriding process in addition to the conventional direct plasma nitriding (DCPN). ASPN has several advantages over the conventional DCPN, such as eliminating the edge effect, arcing, and carrying out hollow cathode discharge.
The sample used was SUS 329J4L (X2CrNiMoCuN25-6-3). Nitriding was carried out at 673 and 723 K for 18 ks by DCPN and ASPN. The nitrided samples were then analyzed by various tests such as appearance observation, X-ray diffraction, SEM-EDX analysis, hardness testing, wear testing, and corrosion testing by measuring the pitting potential. After nitriding, the ASPN process improved the wear resistance and eliminated the edge effect when compared with the DCPN process. The S phase was observed on all the treated samples, and this phase was uniformly formed on both austenitic and ferritic phases of ASPN samples. Moreover, the corrosion tests showed that the pitting potential did not decrease with plasma nitriding. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2010.08.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Recently there has been considerable interest in active screen plasma nitriding (ASPN), through-cage plasma nitriding, and cathodic-cage plasma nitriding. In these processes, the edge effect is completely eliminated because plasma is produced on the cage and not directly on the samples. However, little information has been reported on the effect of the distance between the screen and the sample on the ASPN properties. The objective of this study is to investigate this effect by nitriding low-carbon steel S15C and austenitic stainless steel SUS 304 by ASPN using a 304 steel screen.The sample was treated for 18 ks at 723 K under 600 Pa in 25% N(2) + 75% H(2). The distance between the screen and the sample was changed to 10, 20, 30, 40, and 50 mm. The nitrided samples were characterized by observing their appearance and surface roughness by optical microscopy, scanning electron microscopy, x-ray diffraction, and microhardness testing. After nitriding, polygonal particles with a normal distribution were observed at the entire of all the ASPN-treated sample surfaces. The particles on the sample surface became coarser with a decrease in the distance between the screen and the sample. Furthermore, the thickness of the surface-hardened layer increased with a decrease in the distance between the screen and the sample. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2010.08.034

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Other Link： http://hdl.handle.net/10112/10558

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

The effect of a modified layer caused by pre-deforming on the low temperature plasma nitriding of AISI 304 austenitic stainless steel was investigated. The aim of using the deformed layer is to produce a thicker nitrided layer and to decrease the nitriding temperature due to the much faster diffusion of nitrogen. The pre-deformed sample was prepared by the rolling in 0, 1, 2, 3, and 4% ratios. Plasma nitriding was carried out at 673 and 723 K for 18 ks under 600 Pa pressures in presence of N(2)/H(2) in 50:50 ratio. The microhardness, thickness and phase composition of nitrided layers formed on the surface of pre-deformed and non-deformed samples were investigated using Vickers microhardness tester, optical microscope and X-ray diffraction techniques, respectively. After nitriding, maximum hardness similar to 1150 HV was achieved on the pre-deformed sample. XRD pattern showed that most dominant phase of the nitrided layer consisted of the expanded austenite (S phase). In addition, the pre-deforming by rolling had a significant influence on the hardness and thickness of the S phase. That is, the hardness and thickness of the S phase were increased by applying the pre-deformation.

DOI： 10.4028/www.scientific.net/MSF.654-656.1811

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The intermetallic compound Nb(3)Al is widely investigated because of its high temperature strength, superior superconductivity and relatively small density As Nb(3)Al has an extremely high melting point and lack of deformability, it is impossible to prepare it by using the conventional metallurgy. In this study, a Nb-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Nb and Al foils The process consisted of the accumulative roll-bonding (ARB) for making a laminated Nb/Al sheet and the subsequent heat treatment promoting a solid-phase reaction in the laminated Nb/Al sheet Accumulated foils were roll-bonded at 573 K The rolling reduction at I pass was similar to 50%, and the final rolling reduction at 4 passes was similar to 94%. A pulsed electric current sintering (PECS) process was used for the subsequent heat treatment The microstructures produced at each processing stage were characterized by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (S EM) equipped with energy-dispersive X-ray spectroscopy (EDS). A homogeneous intermetallic compound of Nb(3)Al could be obtained after the subsequent heat treatment for 1.8 ks at 873 K and for 0.9 ks at 1673 K

DOI： 10.4028/www.scientific.net/MSF.638-642.1390

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Low carbon steel S15CK was nitrided by active screen plasma nitriding (ASPN) using various stainless steel cages to investigate the effect of the cage on the nitriding properties. Three types of austenitic stainless steel cages, such as pipe, foil, and wire mesh, were used. The sample was treated for 18 ks at 773 K under 630 Pa in 50% N-2 + 50% H-2 gases. The nitrided samples were characterized by surface roughness tests. optical microscopy, scanning electron microscopy, X-ray diffraction, and microhardness testing. In all samples nitrided by the ASPN process, the 'edging effect' was completely eliminated whereas hardness and thickness of the surface layer were comparable with those obtained front the DC plasma nitriding. Moreover, a comparison of the screens used in the ASPN process revealed that the screen hole size had a slight influence on surface properties such as microstructure and hardness. [doi: 10.2320/matertrans.MRA2008431]

DOI： 10.2320/matertrans.MRA2008431

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This paper reports a study on the effect of a modified layer caused by pre-deforming on the low temperature plasma nitriding of SUS 316 austenitic stainless steel. The pre-deformed sample was prepared by the rolling in 0, 1, 2, 5, and 10% ratios. Plasma nitriding was carried out at 673 and 723 K for 18 ks under 600 Pa pressures in the presence of N(2)/H(2) in 50:50 ratio. After nitriding, maximum hardness similar to 1070 HV was achieved on the pre-deformed sample. XRD pattern showed that the most dominant phase of the nitrided layer consisted of the expanded austenite (S phase). In addition, the pre-deforming by the rolling had a great influence on the increment of hardness and thickness of the S phase.

DOI： 10.1002/ppap.200930707

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Fe3Al intermetallic compound layers were coated on austenitic stainless steel SUS304 by the spark plasma sintering (SPS) process to improve its wear and oxidation resistances. The coating was carried out at 1173 K for 0.6-10.8 ks at a coating pressure of 3-45 MPa. The coatings were densified with increase in the sinter-coating temperature and pressure. The tensile strength of the coatings was 30-50 MPa. These coatings fractured at the interface between the coatings and the substrate. The mass increase of coated specimen after oxidizing at 1123 K for 1000 ks was less than that of the untreated specimen. This result indicates that the Fe-Al intermetallic compound coating markedly improved the oxidation resistance of the austenitic stainless steel.

DOI： 10.1002/ppap.200932407

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Pulsed electric-current sintering (PECS) was applied to the bonding of SiC (pressureless-sintered silicon carbide) to Cu (oxygen-free copper) using a mixture of Cu and Ti powders as an intermediate layer. The influences of the intermediate powders on the bond strength of the joint were investigated by observation of the microstructure. The bonding was carried out at carbon-die temperatures from 973 to 1173 K at a bonding pressure of 10 MPa for 3.6 ks. The application of intermediate layers of 100% Ti, 95% Ti + 5% Cu, and 5% Ti + 95% Cu remarkably improved the bond strength as compared with direct bonding without an intermediate powder. SEM observations of the joint with the intermediate powders revealed that a Cu solid-solution layer, a TiC layer, and a Ti5Si3 layer had covered most of the interface, similar to those observed in the friction-bonded and pulsed-electric current bonded joints of SiC to Cu in which the application of a Ti foil as an intermediate layer remarkably improved the bond strength.

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Iron aluminides exhibit good resistance to high-temperature oxidizing and sulphidizing environments and have potential for structural applications at high temperatures under corrosive environments. In this study, an Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The process consisted of the accumulative roll-bonding (ARB) for making a laminated Fe/Al sheet and the subsequent heat treatment promoting a solid-phase reaction in the laminated Fe/Al sheet. Accumulated foils were rolled and bonded at room temperature or 573 K. A pulsed electric current sintering (PECS) process was used for the subsequent heat treatment. The microstructures produced at each processing stage were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). Vickers microhardness testing was used for hardness determination. A homogeneous intermetallic compound of Fe3Al or FeAl could be obtained after the subsequent heat treatment for 1.8 ks at 873 K and for 3.6 ks at 1173 K.

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Pulsed electric current sintering (PECS) was applied to the bonding of W (tungsten) to Cu (copper) using Nb or Ni powder as an intermediate layer. The influence of the intermediate layer on the bond strength of the joint was investigated by observation of the microstructure. The bonding process was carried out at carbon-die temperatures of 1073 and 1173 K for 1.8 ks at a bonding pressure of 130 MPa. The bond strength of the joint with an intermediate layer of Ni powder was 250 MPa. This joint fractured in the Cu base during the tensile test. SEM observations of the joint with an intermediate layer of Ni revealed that a diffusion layer formed at the joint interface.

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Other Link： http://hdl.handle.net/10112/1597

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Language：English   Publishing type：Part of collection (book)   Publisher：Elsevier  

The simultaneous deposition of chromium and silicon on austenitic stainless steel SUS310S using a halide-activated diffusion coating process is performed in order to improve oxidation and wear properties at high temperatures. The specimen placed in an A12O3 crucible is filled with a powder containing Cr-Si powder, a halide activator of NH4CI, NaF, A1F3, and an A12O3 filler powder. The diffusion-coating treatment is carried out at 1073-1323 Kelvin (K) for 18 ks in argon atmosphere. Simultaneous diffusion-coating layers are mainly characterized chromium silicide and alpha ferrite. An oxidation characteristic after diffusion coating is investigated for 1000 ks at 1073 K in air. The mass increase of diffusion-coated specimen is less than that of the untreated specimen. This result indicates that the simultaneous deposition of chromium (Cr) and silicon (Si) markedly improved the oxidation resistance of the austenitic stainless steel. © 2005 Elsevier Ltd.

DOI： 10.1016/B978-008044504-5/50089-1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER CERAMIC SOC  

The interfacial microstructure of a SiC/Cu joint friction-bonded with a Ti intermediate layer has been characterized with TEM to determine the process by which Interfacial layers of mainly TIC and a Cu-alloy (adjacent to the SIC matrix) form. The formation of these layers Is greatly suppressed by water quenching just after the forging stage. In the quenched joint, almost the entire interface is comprised of a Ti-rich layer a few nm thick. TEM observations of the interface after reheating quenched joints at 1073 K and 773 K indicate that the reaction to form the TiC and the Cu-alloy layers can proceed at 1073 K but not at 773 K. These results suggest that the formation of the TiC and Cu-alloy layers starts during the forging stage, and that the layers grow at temperatures higher than 773 K during the cooling process.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANSACTIONS MATERIALS & HEAT TREATMENT  

In order to prepare a hypereutectic Al-Si alloy with low coefficients of thermal expansion (CTE), Al-50%Si alloy was produced by powder metallurgy (P/M) and ingot metallurgy (I/M). P/M specimen was prepared by mechanical alloying (MA) and pulsed electric-current sintering (PECS). The microstructures of specimens were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Vickers microhardness and CTE measurements were performed. The grains in the P/M specimen were refined with increasing MA time. Primary Si and eutectic Si in the I/M specimen were remarkably refined by adding minute amounts of Sr. The CTE of P/M and I/M specimens were estimated as 7.8x10(-6) and 10.7x10(-6), respectively. These values were as same as a CTE of Al2O3 ceramics.

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Iron aluminides exhibit good resistance to high-temperature sulfidizing and oxidizing environments and potential for structural applications at high temperatures under corrosive environments. In this study, Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The process consisted of the accumulative roll-bonding (ARB) for making a laminated Fe/Al sheet and the subsequent heat treatment promoting a solid phase reaction in the laminated Fe/Al sheet. The microstructures produced at each processing stage were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Vickers microhardness testing was used for hardness determination. A homogeneous intermetallic compound of Fe3Al or FeAl could be obtained after the subsequent heat treatment for 1.8 ks at 973 K and for 10.8 ks at 1123 or 1173 K.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANSACTIONS MATERIALS & HEAT TREATMENT  

Iron aluminides exhibit good resistance to high-temperature sulfidizing and oxidizing environments and potential for structural applications at high temperatures under corrosive environments. In this study, Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The process consisted of the accumulative roll-bonding (ARB) for making a laminated Fe/Al sheet and the subsequent heat treatment promoting a solid phase reaction in the laminated Fe/Al sheet. The microstructures produced at each processing stage were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Vickers microhardness testing was used for hardness determination. A homogeneous intermetallic compound of Fe3Al or FeAl could be obtained after the subsequent heat treatment for 1.8 ks at 973 K and for 10.8 ks at 1123 or 1173 K.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

In order to discuss the effect of a Ti intermediate layer on the strength of the friction-bonded joint of silicon carbide to copper, the microstructure of the joint interface was observed with a TEM. Specimens to be bonded were rods of pressureless-sintered SiC and oxygen-free copper. TEM observations revealed that reaction layers less than a few 10 nm thick were formed, which were identified as Cu, TiC, and Ti5Si3 On the basis of SAD pattern and EDX analyses. The Ti5Si3 layer was partly formed as discrete islands on the Cu side of the TiC layer. The Cu layer was located between SiC matrix and TiC layer, forming TiC/Cu double layers. The TiC/Cu double layers presented preferred orientation relationships with SiC, which can be expressed by the following equations.
(10 (1) over bar2)(6H-SiC)//(1 (1) over bar1)(TiC), [1 (2) over bar 10](6H-SiC)//[110](TiC)
(10 (1) over bar2)(6H-SiC)//(1 (1) over bar1)(Cu), [1 (2) over bar 10](6H-SiC)//[110](Cu)
On the other hand, the Ti5Si3 layer showed no preferred orientation relationship with SiC or Cu. In addition to these reaction layers, amorphous layers of Si oxide similar to100 nm thick were occasionally observed at the SiC/Cu interface. In the Cu-Ti mixing region adjacent to the joint interface, Cu4Ti particles similar to100 nm size in diameter were observed.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

The bonding of SiC (pressureless-sintered silicon carbide) and Cu (oxygen-free copper) with a Ti intermediate layer was carried out using pulsed electric-current sintering. The influences of the intermediate layer on the bond strength and the microstructure of the joint were then investigated by SEM and TEM observations. The bonding conditions were varied between 923-1173 K for 1.8-3.6 ks under a constant bonding pressure of 24 MPa. The bond strength of SiC to Cu with a Ti intermediate layer showed marked improvement, whereas the direct bonding without an intermediate layer resulted in the separation of SiC from the Cu specimen immediately after the bonding operation without any application of external load. TEM observations of the joint interface with the Ti intermediate layer revealed that a TiC layer similar to300 nm thick and a Cu solid-solution layer similar to70 nm thick had covered most of the interface, with the Cu layer formed between the TiC layer and the SiC matrix.

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Language：Japanese   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.54.200

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ASM INTERNATIONAL  

The materials used at high temperatures have recently been required more severe properties than before. The method of the diffusion coating of silicon and chromium to the surface of a metallic materials is effective to improve oxidation and wear properties at high temperatures. The combined method of the diffusion coating processing and carburizing, or nitriding are now of this investigation.
The obtained layer by the co-diffusion coating processing of Si and Cr depends on the composition of pack powders and the kinds of the activator. In this study, the co-diffusion coating processing of Si and Cr was done for various stainless steels. The, mixing ratio of pack powders and the kinds of the activator were investigated, and also mechanical and oxidation properties at high temperatures were studied.

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Iron aluminides exhibit good resistance to high-temperature sulfidizing and oxidizing environments and potential for structural applications at high temperatures under corrosive environments. In this study, Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The microstructures produced at each processing stage were characterized by optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDS). Vickers microhardness; testing was used for hardness determination. Four layers composed of FeAl3, Fe2Al5, FeAl2, and FeAl were observed at the Fe/Al interface after diffusion annealing. Annealing process of Fe foils before roll-bonding and process-annealing during roll-bonding suggested a better process to obtain a homogeneous Fe-Al intermetallic compound.

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Intermediate layers of various metals ranging from reactive metals to noble metals have been applied to friction bonding of SiC (pressureless-sintered silicon carbide) to Cu (oxygen-free copper), and their influences on the bond strength and microstructures of the joint have been systematically investigated by means of TEM observations. When a thin foil of reactive metal, Al, Ti, Zr, or Nh, was applied as the intermediate layer, the bond strength of SIC to Cu was improved considerably. In contrast, when an intermediate layer of Fe, Ni, or Ag was applied, the SiC specimen separated from the Cu specimen immediately after the bonding operation without the application of external load, similar to the cast: of bonding without an intermediate layer. During friction bonding with an intermediate layer of reactive metal, the intermediate layer was mechanically mixed with Cu to form a very complicated microstructure extending over a region as wide as a few 100 mum. TEM observations have revealed that very thin reaction layers between the SIC and reactive metals were formed. When die Ti intermediate layer was applied, a TiC layer 10-30 nm thick was formed over almost the entire area along the interface, and between this layer and the SIC matrix a very thin layer of a Cu solid solution was detected. On the other side of the TiC layer, a Ti5Si3 layer similar to 100 nm thick was partially observed. When the Nb or Zr intermediate layer was applied, a very thin interfacial layer, in which Nb or Zr was significantly concentrated, was observed in addition to the reaction layers of Nb5Si3, NbC, and ZrC. These interfacial layers can be characterized by their much smaller thickness and finer grain size than those observed in diffusion-bonded and brazed joints. Apart from the layers mentioned above, amorphous silicon oxide layers were occasionally observed, suggesting that the reactive metal enhanced the removal of the oxide film on the SIC surface.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

The influences of the interfacial reaction on the microstructure and bond strength of the SiC/Cu joint friction-bonded with a Nb intermediate layer have been investigated mainly by TEM observations. It has been found that the reaction at the joint interface proceeded during the heat treatment even at temperatures below 800 K to form reaction layers approximately 100 nm thick, which caused serious degradation of the joint strength. An attempt is made to thermodynamically explain the evolution of the interfacial microstructure caused by the reaction during the heat treatment.

DOI： 10.2320/matertrans1989.40.953

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Intermediate layers of various metals ranging from reactive metals to noble metals have been applied to the friction bonding of SiC (pressureless-sintered silicon carbide) to Cu (oxygen free copper), and their influences on the bond strength and microstructures of the joint have been systematically investigated by TEM observations. When thin foils of reactive metals Al, Ti, Zr, and Nb were applied as the intermediate layer, the bond strength of SiC to Cu was improved remarkably. In contrast, when intermediate layers of Fe, Ni, and Ag were applied, the SiC specimen separated from the Cu specimen immediately after the bonding operation without application of external load, similarly to the case of bonding without an intermediate layer. In the joint bonded with the intermediate layers of the reactive metals, the intermediate layer was mechanically mixed with Cu to form a mixed region as wide as a few 100 μm. TEM observations have revealed that very thin reaction layers between the ceramics and reactive metals formed. When the Ti intermediate layer was applied, a TiC layer 10-30 nm thick formed over the almost whole interface, and between this layer and the SiC matrix a very thin layer of a Cu solid-solution was detected. On the other side of the TiC layer, a Ti5Si3 layer approximately 100 nm thick was partially observed. When the Nb and Zr intermediate layers were applied, very thin interfacial layers where Nb and Zr were significantly concentrated were observed in addition to the reaction layers of Nb5Si3, NbC and ZrC. These interfacial layers can be characterized by their much smaller thickness and finer grain size than those observed in diffusion-bonded and brazed joints. Apart from the layers mentioned above, amorphous silicon oxide layers were occasionally observed, suggesting that the reactive metal enhanced the removal of the oxide film on the SiC surface.

DOI： 10.2320/jinstmet1952.63.7_895

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Language：English   Publisher：WILEY-BLACKWELL  

Fe3Al intermetallic compound layers were coated on austenitic stainless steel SUS304 by the spark plasma sintering (SPS) process to improve its wear and oxidation resistances. The coating was carried out at 1173 K for 0.6-10.8 ks at a coating pressure of 3-45 MPa. The coatings were densified with increase in the sinter-coating temperature and pressure. The tensile strength of the coatings was 30-50 MPa. These coatings fractured at the interface between the coatings and the substrate. The mass increase of coated specimen after oxidizing at 1123 K for 1000 ks was less than that of the untreated specimen. This result indicates that the Fe-Al intermetallic compound coating markedly improved the oxidation resistance of the austenitic stainless steel.

DOI： 10.1002/ppap.200932407

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http://hdl.handle.net/10112/1628

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Pulsed electric-current sintering (PECS) was applied to the bonding of SiC (pressureless-sintered silicon carbide) to Cu (oxygen-free copper) using a mixture of Cu and Ti powders as an intermediate layer. The influences of the intermediate powders on the bond strength of the joint were investigated by observation of the microstructure. The bonding was carried out at carbon-die temperatures from 973 to 1173 K at a bonding pressure of 10 MPa for 3.6 ks. The application of intermediate layers of 100% Ti, 95% Ti + 5% Cu, and 5% Ti + 95% Cu remarkably improved the bond strength as compared with direct bonding without an intermediate powder. SEM observations of the joint with the intermediate powders revealed that a Cu solid-solution layer, a TiC layer, and a Ti5Si3 layer had covered most of the interface, similar to those observed in the friction-bonded and pulsed-electric current bonded joints of SiC to Cu in which the application of a Ti foil as an intermediate layer remarkably improved the bond strength.

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Language：English   Publisher：TRANS TECH PUBLICATIONS LTD  

Iron aluminides exhibit good resistance to high-temperature oxidizing and sulphidizing environments and have potential for structural applications at high temperatures under corrosive environments. In this study, an Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The process consisted of the accumulative roll-bonding (ARB) for making a laminated Fe/Al sheet and the subsequent heat treatment promoting a solid-phase reaction in the laminated Fe/Al sheet. Accumulated foils were rolled and bonded at room temperature or 573 K. A pulsed electric current sintering (PECS) process was used for the subsequent heat treatment. The microstructures produced at each processing stage were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). Vickers microhardness testing was used for hardness determination. A homogeneous intermetallic compound of Fe3Al or FeAl could be obtained after the subsequent heat treatment for 1.8 ks at 873 K and for 3.6 ks at 1173 K.

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http://www.scientific.net/3-908451-33-7/289/

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：関西大学  

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Language：English   Publisher：TRANSACTIONS MATERIALS & HEAT TREATMENT  

Iron aluminides exhibit good resistance to high-temperature sulfidizing and oxidizing environments and potential for structural applications at high temperatures under corrosive environments. In this study, Fe-Al intermetallic compound was prepared by multi-layered roll-bonding of elemental Fe and Al foils. The process consisted of the accumulative roll-bonding (ARB) for making a laminated Fe/Al sheet and the subsequent heat treatment promoting a solid phase reaction in the laminated Fe/Al sheet. The microstructures produced at each processing stage were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Vickers microhardness testing was used for hardness determination. A homogeneous intermetallic compound of Fe3Al or FeAl could be obtained after the subsequent heat treatment for 1.8 ks at 973 K and for 10.8 ks at 1123 or 1173 K.

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Language：English   Publisher：TRANSACTIONS MATERIALS & HEAT TREATMENT  

In order to prepare a hypereutectic Al-Si alloy with low coefficients of thermal expansion (CTE), Al-50%Si alloy was produced by powder metallurgy (P/M) and ingot metallurgy (I/M). P/M specimen was prepared by mechanical alloying (MA) and pulsed electric-current sintering (PECS). The microstructures of specimens were characterized by optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Vickers microhardness and CTE measurements were performed. The grains in the P/M specimen were refined with increasing MA time. Primary Si and eutectic Si in the I/M specimen were remarkably refined by adding minute amounts of Sr. The CTE of P/M and I/M specimens were estimated as 7.8x10(-6) and 10.7x10(-6), respectively. These values were as same as a CTE of Al2O3 ceramics.

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Language：Japanese  

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Language：Japanese  

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Language：Japanese   Publisher：関西大学  

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Language：Japanese   Publisher：日本工業炉協会  

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：関西大学  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

CiNii Books

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Language：Japanese   Publisher：Japan Welding Society  

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Language：Japanese   Publisher：Japan Welding Society  

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Venue：沖縄コンベンションセンター  

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Venue：沖縄コンベンションセンター  

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Venue：Osaka, Japan  

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Event date： 2011.5

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Venue：東京工業大学  

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Event date： 2011.5

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Event date： 2010.11

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Venue：名城大  

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Event date： 2009.10

Venue：Beijing, China  

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Event date： 2008.12

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Event date： 2008.12

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Venue：Vienna, Austria  

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