The Experts below are selected from a list of 2574 Experts worldwide ranked by ideXlab platform
Hui Zhang - One of the best experts on this subject based on the ideXlab platform.
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Enhanced toughness of Nitrided layers formed on Ti-6Al-4V alloy via surface mechanical attrition pre-treatment
Vacuum, 2017Co-Authors: Quantong Yao, Weiping Tong, Jian Sun, Guanglan Zhang, Hui ZhangAbstract:Abstract This study focused on developing a beneficial nitriding process for use on Ti-6Al-4V alloy surfaces, involving surface mechanical attrition treatment (SMAT), which does not contaminate the existing nanocrystalline layer. The average grain size of this layer was refined to 10 nm with random crystallographic orientation. Differential scanning calorimetry confirmed that the recrystallization temperature of the Ti-6Al-4V nanocrystalline layer was 550 °C. The phase compositions, microstructure, hardness and toughness of the Nitrided layer were studied by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and hardness testing. The Nitrided layer of the SMAT Sample was composed of nanoscale TiN, Ti 2 N and Ti with high nitrogen supersaturation. The nitriding kinetics was enhanced by the nanocrystalline layer at relatively low temperatures (600 °C). Compared to coarse-grained Nitrided Samples, the SMAT Nitrided Sample exhibited similar surface hardness but improved surface toughness, which may be attributed to the formation of a nanostructured Nitrided layer.
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Enhanced strength and plasticity of gas Nitrided iron by surface mechanical attrition pretreatment
Surface and Coatings Technology, 2016Co-Authors: Jian Sun, W.p. Tong, Hui ZhangAbstract:Abstract Nitriding treatment at 520 °C for 6 h was performed on a pure iron plate (1.5 mm thick) with nanostructured surface layer, produced by surface mechanical attrition treatment (SMAT). Microstructure, surface hardness and tensile behavior of SMAT Nitrided Sample were investigated compared to those of coarse-grained Nitrided Sample. Experimental results showed that a much thicker compound layer and a unique transition zone were developed on the SMAT Nitrided Sample, leading to an obvious enhancement in surface hardness. Tensile tests revealed that the SMAT Nitrided Sample exhibits an ultimate tensile strength of ~ 450 MPa with a total elongation of ~ 44%, which is much higher than that of the coarse-grained Nitrided counterpart (390 MPa, 18%). The higher tensile strength of the SMAT Nitrided Sample may originate from the contribution of a much thicker compound layer and a unique transition zone. The extraordinary tensile plasticity may benefit from that the precipitation of needle-like nitrides layer was hindered on the SMAT Nitrided Sample. This enhanced processing method demonstrates the technological significance of nanomaterials in improving traditional processing techniques and provides a new approach to obtain ferrous materials with excellent surface properties and outstanding global tensile properties simultaneously.
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evaluation of surface modified 20crmo by plasma nitriding coupled with ion sputtering and smat
Surface & Coatings Technology, 2012Co-Authors: W.p. Tong, Hui Zhang, Z B WangAbstract:Abstract Plasma nitriding treatment is a well-established method of improving the wear and corrosion properties of steel materials by the formation of a unique composite structure with a hard surface layer and a tough interior. However, the toughness of the Nitrided layer that arises from the nitriding treatment is substantially lower than the underlying substrate. This paper describes the combined treatment of ion sputtering and SMAT on a Nitrided steel Sample which leads to the decomposition of the compound layer and the formation of a nanostructured diffusion layer. Optical microscopy, transmission electron microscopy, X-ray diffraction and microhardness testing were used to investigate the structure and mechanical properties of the modified surface layer in comparison with those of the Nitrided Sample. The result indicates that a nanostructured diffusion surface layer with satisfactory hardness and wear properties was formed on the treated Sample relative to that of the conventional Nitrided Sample. Especially, the toughness of surface layer was greatly improved by this combined treatment. This method demonstrates the technological significance of SMAT in improving traditional processing techniques. It also provides a new approach for preparation of a Nitrided surface layer with high strength and high toughness.
W.p. Tong - One of the best experts on this subject based on the ideXlab platform.
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simultaneously improving surface mechanical properties and in vitro biocompatibility of pure titanium via surface mechanical attrition treatment combined with low temperature plasma nitriding
Surface & Coatings Technology, 2017Co-Authors: Y H Zhang, X D Du, Yu Cheng Wu, W.p. TongAbstract:Abstract In this paper, low-temperature plasma nitriding at 550 °C for 4 h was performed on a pure titanium Sample with nanostructured surface layer induced by surface mechanical attrition treatment (SMAT). Microstructure, surface topography, surface mechanical properties and in vitro biocompatibility of SMAT Nitrided titanium Sample were investigated in comparison with those of original and SMATed Samples. Experimental results revealed that a nanostructured nitrides layer was fabricated on the surface of SMAT Nitrided titanium Sample, leading to enhance the surface hardness and to reduce wear volume. Additionally, the surface roughness and wettability of SMAT Nitrided Sample are different from those of the original and SMATed Samples. Furthermore, the SMAT Nitrided Sample exhibits promoted cell attachment, proliferation and differentiation compared to those of the original and SMATed Samples. The enhanced cell response on SMAT Nitrided Sample may be originated from its unique surface characteristics, such as surface “nano-effect”, formation of titanium nitrides and enhanced wettability, etc. This composite surface treatment may provide a promising method to improve surface mechanical properties and in vitro response of titanium implants simultaneously.
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Gas Nitriding of High-Vanadium Alloy Steel
Materials Science Forum, 2016Co-Authors: Hai Zhi Li, W.p. TongAbstract:A composite surface layer was fabricated on a high-vanadium alloy steel (HVAS) plate by means of a surface gas nitriding at 550°C for 70h. The microstructural charaterization and phase analysis of resultant nitride layers were performed using optical, scanning electron microscopy, electron probe microanalyzer, X-ray diffraction methods and hardness measurements. The results of the investigation showed that a composite layer consisting of e-Fe2–3N and γ'-Fe4N phases is feasible on the surface of HVAS. Vickers hardness test indicate that the hardness value of the Nitrided Sample is about 1100 HV at the top surface, and decreases gradually to about 700 HV in the matrix. The depth of hardened layer after surface gas nitriding was about 200 μm.
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Enhanced strength and plasticity of gas Nitrided iron by surface mechanical attrition pretreatment
Surface and Coatings Technology, 2016Co-Authors: Jian Sun, W.p. Tong, Hui ZhangAbstract:Abstract Nitriding treatment at 520 °C for 6 h was performed on a pure iron plate (1.5 mm thick) with nanostructured surface layer, produced by surface mechanical attrition treatment (SMAT). Microstructure, surface hardness and tensile behavior of SMAT Nitrided Sample were investigated compared to those of coarse-grained Nitrided Sample. Experimental results showed that a much thicker compound layer and a unique transition zone were developed on the SMAT Nitrided Sample, leading to an obvious enhancement in surface hardness. Tensile tests revealed that the SMAT Nitrided Sample exhibits an ultimate tensile strength of ~ 450 MPa with a total elongation of ~ 44%, which is much higher than that of the coarse-grained Nitrided counterpart (390 MPa, 18%). The higher tensile strength of the SMAT Nitrided Sample may originate from the contribution of a much thicker compound layer and a unique transition zone. The extraordinary tensile plasticity may benefit from that the precipitation of needle-like nitrides layer was hindered on the SMAT Nitrided Sample. This enhanced processing method demonstrates the technological significance of nanomaterials in improving traditional processing techniques and provides a new approach to obtain ferrous materials with excellent surface properties and outstanding global tensile properties simultaneously.
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evaluation of surface modified 20crmo by plasma nitriding coupled with ion sputtering and smat
Surface & Coatings Technology, 2012Co-Authors: W.p. Tong, Hui Zhang, Z B WangAbstract:Abstract Plasma nitriding treatment is a well-established method of improving the wear and corrosion properties of steel materials by the formation of a unique composite structure with a hard surface layer and a tough interior. However, the toughness of the Nitrided layer that arises from the nitriding treatment is substantially lower than the underlying substrate. This paper describes the combined treatment of ion sputtering and SMAT on a Nitrided steel Sample which leads to the decomposition of the compound layer and the formation of a nanostructured diffusion layer. Optical microscopy, transmission electron microscopy, X-ray diffraction and microhardness testing were used to investigate the structure and mechanical properties of the modified surface layer in comparison with those of the Nitrided Sample. The result indicates that a nanostructured diffusion surface layer with satisfactory hardness and wear properties was formed on the treated Sample relative to that of the conventional Nitrided Sample. Especially, the toughness of surface layer was greatly improved by this combined treatment. This method demonstrates the technological significance of SMAT in improving traditional processing techniques. It also provides a new approach for preparation of a Nitrided surface layer with high strength and high toughness.
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Plasma Nitriding of 20CrMo Steel with Nanostructured Surface Layer
Advanced Materials Research, 2012Co-Authors: Jian Sun, W.p. Tong, Jing Zhang, Liang ZuoAbstract:A nanostructured surface layer was produced on an 20CrMo steel plate by means of ultrasonic shot peening (USSP) treatment. Plasma nitriding of the treated and un-treated Sample were investigated by using structure analysis (X-ray diffraction, optical microscopy, and transmission electron microscopy ) as well as hardness measurements. It was found that a nanostructured surface layer Sample developed a compound layer twice as thick as that in a coarse-grained Sample under the same plasma nitriding conditions (530 oC for 6 h). In addition, the USSP Nitrided Sample exhibited higher hardness and thicker hardened surface layer in comparison with coarse-grained Nitrided Sample.
M S J Hashmi - One of the best experts on this subject based on the ideXlab platform.
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Structural and tribological properties of the plasma Nitrided Ti-alloy biomaterials: Influence of the treatment temperature
Surface & Coatings Technology, 2006Co-Authors: Mahfujur Rahman, I. Reid, P. Duggan, Denis P. Dowling, Greg Hughes, M S J HashmiAbstract:Abstract Plasma Enhanced Chemical Vapor Deposition (PECVD) based saddle field fast atom beam source is a potential method for the nitriding of the Ti-based alloy at low pressure. In this study, influence of the nitriding temperature on the structural and the tribological properties of the low-pressure plasma Nitrided Ti–6Al–4V alloy have been investigated. The cross-sectional optical investigation of the Nitrided Samples confirmed presence of a compound Nitrided layer when nitriding was performed at high temperature and growth of this layer was found increased as nitriding temperature increased. X-ray diffraction result showed that the formation of the TiN phase commenced at high temperature and the concentration of this phase found increased as nitriding temperature increased. X-ray Photoelectronic Spectroscopy result also confirmed existence of the TiN as well as the TiN x O y phase in nitride layer. Micro hardness tests showed temperature depended hardness properties of the Nitrided Samples and a noticeable increase in the hardness value was observed for Sample Nitrided at 900 °C. Pin-on-disk test result confirmed an improvement of the tribological property of the Nitrided Sample comparing with the untreated Sample. However, the Samples Nitrided at high temperature exhibited significantly decreased of the friction co-efficient and the wear depth value compared with the untreated and the low temperature Nitrided (temperature below 700 °C) Samples.
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low temperature plasma nitriding of 316 stainless steel by a saddle field fast atom beam source
Surface & Coatings Technology, 2005Co-Authors: Mahfujur Rahman, Julfikar Haider, M S J HashmiAbstract:Nitriding by plasma is a promising method for surface treatment to improve hardness, corrosion, wear and fatigue resistance of materials (ferrous and non-ferrous). But in conventional plasma nitriding techniques, the processing temperature depends on plasma process parameters and it cannot be controlled independently of the plasma source. In this present work, a new low temperature and low pressure plasma nitriding process on AISI 316 stainless steel Sample by a saddle field fast atom beam source is reported. Plasma nitriding was carried out at 420 °C and at a pressure of 0.1 Pa for 8 h. Optical microscopy investigation of the cross-section of the Nitrided Sample revealed a thin Nitrided layer separated from the core material by a distinct etch line. Irregular surface morphology similar to austenitic grain boundaries was visible on the surface of the Nitrided Sample when viewed under Scanning Electron Microscope. Energy dispersive X-ray spectroscopy study showed the presence of nitrogen in the Nitrided surface whereas no nitrogen was found in the non-Nitrided Sample. The crystal structure of expanded austenite or S phase was identified by X-ray diffraction analysis without any CrN precipitation. A high hardness value on the Nitrided surface and in the Nitrided layer in comparison with a low value of hardness in the core material was observed by Vickers microhardness testing. The results show that this is a promising method for low temperature plasma nitriding of austenitic stainless steel.
Jian Sun - One of the best experts on this subject based on the ideXlab platform.
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Enhanced toughness of Nitrided layers formed on Ti-6Al-4V alloy via surface mechanical attrition pre-treatment
Vacuum, 2017Co-Authors: Quantong Yao, Weiping Tong, Jian Sun, Guanglan Zhang, Hui ZhangAbstract:Abstract This study focused on developing a beneficial nitriding process for use on Ti-6Al-4V alloy surfaces, involving surface mechanical attrition treatment (SMAT), which does not contaminate the existing nanocrystalline layer. The average grain size of this layer was refined to 10 nm with random crystallographic orientation. Differential scanning calorimetry confirmed that the recrystallization temperature of the Ti-6Al-4V nanocrystalline layer was 550 °C. The phase compositions, microstructure, hardness and toughness of the Nitrided layer were studied by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and hardness testing. The Nitrided layer of the SMAT Sample was composed of nanoscale TiN, Ti 2 N and Ti with high nitrogen supersaturation. The nitriding kinetics was enhanced by the nanocrystalline layer at relatively low temperatures (600 °C). Compared to coarse-grained Nitrided Samples, the SMAT Nitrided Sample exhibited similar surface hardness but improved surface toughness, which may be attributed to the formation of a nanostructured Nitrided layer.
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Fabrication of Microalloy Nitrided Layer on Low Carbon Steel by Nitriding Combined with Surface Nano-Alloying Pretreatment
Coatings, 2016Co-Authors: Jian Sun, Quantong YaoAbstract:Surface mechanical attrition treatment (SMAT) is an effective method to accelerate the nitriding process of metallic materials. In this work, a novel technique named surface nano-alloying (SNA) was developed on the basis of surface mechanical attrition treatment, which was employed as a pretreatment for the nitriding of low carbon steel materials. The microstructure and surface properties of treated Samples were investigated by SEM, XRD, TEM and the Vickers hardness test. Experimental results showed that a surface alloying layer (Cr element) of about 10–20 μm in thickness was formed on the low carbon steel Sample after the surface nano-alloying treatment. After nitriding for the SNA Sample, a complex compound layer composed of Fe2–3N, FeCr and Cr2N phases was fabricated. Moreover, the thickness of this compound layer was about 50 μm. Meanwhile, both the surface hardness and wear resistance of the SNA Nitrided Sample are better that those of the SMAT Nitrided Sample. This work offers a new approach for improving the nitriding process of steel materials.
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Enhanced strength and plasticity of gas Nitrided iron by surface mechanical attrition pretreatment
Surface and Coatings Technology, 2016Co-Authors: Jian Sun, W.p. Tong, Hui ZhangAbstract:Abstract Nitriding treatment at 520 °C for 6 h was performed on a pure iron plate (1.5 mm thick) with nanostructured surface layer, produced by surface mechanical attrition treatment (SMAT). Microstructure, surface hardness and tensile behavior of SMAT Nitrided Sample were investigated compared to those of coarse-grained Nitrided Sample. Experimental results showed that a much thicker compound layer and a unique transition zone were developed on the SMAT Nitrided Sample, leading to an obvious enhancement in surface hardness. Tensile tests revealed that the SMAT Nitrided Sample exhibits an ultimate tensile strength of ~ 450 MPa with a total elongation of ~ 44%, which is much higher than that of the coarse-grained Nitrided counterpart (390 MPa, 18%). The higher tensile strength of the SMAT Nitrided Sample may originate from the contribution of a much thicker compound layer and a unique transition zone. The extraordinary tensile plasticity may benefit from that the precipitation of needle-like nitrides layer was hindered on the SMAT Nitrided Sample. This enhanced processing method demonstrates the technological significance of nanomaterials in improving traditional processing techniques and provides a new approach to obtain ferrous materials with excellent surface properties and outstanding global tensile properties simultaneously.
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Plasma Nitriding of 20CrMo Steel with Nanostructured Surface Layer
Advanced Materials Research, 2012Co-Authors: Jian Sun, W.p. Tong, Jing Zhang, Liang ZuoAbstract:A nanostructured surface layer was produced on an 20CrMo steel plate by means of ultrasonic shot peening (USSP) treatment. Plasma nitriding of the treated and un-treated Sample were investigated by using structure analysis (X-ray diffraction, optical microscopy, and transmission electron microscopy ) as well as hardness measurements. It was found that a nanostructured surface layer Sample developed a compound layer twice as thick as that in a coarse-grained Sample under the same plasma nitriding conditions (530 oC for 6 h). In addition, the USSP Nitrided Sample exhibited higher hardness and thicker hardened surface layer in comparison with coarse-grained Nitrided Sample.
Mahfujur Rahman - One of the best experts on this subject based on the ideXlab platform.
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Structural and tribological properties of the plasma Nitrided Ti-alloy biomaterials: Influence of the treatment temperature
Surface & Coatings Technology, 2006Co-Authors: Mahfujur Rahman, I. Reid, P. Duggan, Denis P. Dowling, Greg Hughes, M S J HashmiAbstract:Abstract Plasma Enhanced Chemical Vapor Deposition (PECVD) based saddle field fast atom beam source is a potential method for the nitriding of the Ti-based alloy at low pressure. In this study, influence of the nitriding temperature on the structural and the tribological properties of the low-pressure plasma Nitrided Ti–6Al–4V alloy have been investigated. The cross-sectional optical investigation of the Nitrided Samples confirmed presence of a compound Nitrided layer when nitriding was performed at high temperature and growth of this layer was found increased as nitriding temperature increased. X-ray diffraction result showed that the formation of the TiN phase commenced at high temperature and the concentration of this phase found increased as nitriding temperature increased. X-ray Photoelectronic Spectroscopy result also confirmed existence of the TiN as well as the TiN x O y phase in nitride layer. Micro hardness tests showed temperature depended hardness properties of the Nitrided Samples and a noticeable increase in the hardness value was observed for Sample Nitrided at 900 °C. Pin-on-disk test result confirmed an improvement of the tribological property of the Nitrided Sample comparing with the untreated Sample. However, the Samples Nitrided at high temperature exhibited significantly decreased of the friction co-efficient and the wear depth value compared with the untreated and the low temperature Nitrided (temperature below 700 °C) Samples.
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low temperature plasma nitriding of 316 stainless steel by a saddle field fast atom beam source
Surface & Coatings Technology, 2005Co-Authors: Mahfujur Rahman, Julfikar Haider, M S J HashmiAbstract:Nitriding by plasma is a promising method for surface treatment to improve hardness, corrosion, wear and fatigue resistance of materials (ferrous and non-ferrous). But in conventional plasma nitriding techniques, the processing temperature depends on plasma process parameters and it cannot be controlled independently of the plasma source. In this present work, a new low temperature and low pressure plasma nitriding process on AISI 316 stainless steel Sample by a saddle field fast atom beam source is reported. Plasma nitriding was carried out at 420 °C and at a pressure of 0.1 Pa for 8 h. Optical microscopy investigation of the cross-section of the Nitrided Sample revealed a thin Nitrided layer separated from the core material by a distinct etch line. Irregular surface morphology similar to austenitic grain boundaries was visible on the surface of the Nitrided Sample when viewed under Scanning Electron Microscope. Energy dispersive X-ray spectroscopy study showed the presence of nitrogen in the Nitrided surface whereas no nitrogen was found in the non-Nitrided Sample. The crystal structure of expanded austenite or S phase was identified by X-ray diffraction analysis without any CrN precipitation. A high hardness value on the Nitrided surface and in the Nitrided layer in comparison with a low value of hardness in the core material was observed by Vickers microhardness testing. The results show that this is a promising method for low temperature plasma nitriding of austenitic stainless steel.