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Chang Q. Sun - One of the best experts on this subject based on the ideXlab platform.
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Interfacial structure, residual stress and adhesion of Diamond Coatings deposited on titanium
Thin Solid Films, 2003Co-Authors: Chang Q. SunAbstract:Abstract The interfacial structures of Diamond Coatings deposited on pure titanium substrate were analyzed using scanning electron microscopy and grazing incidence X-ray diffraction. Results showed that beneath the Diamond Coating, there was one titanium carbide and hydride interlayer, followed by a heat-affected and carbon/hydrogen diffused Ti layer. Residual stress in the Diamond Coating and TiC interlayer under different process parameters were measured using Raman and X-ray diffraction (XRD) methods. Diamond Coatings showed large compressive stress on the order of a few giga Pascal. XRD analysis also showed the presence of compressive stress in the TiC interlayer and tensile stress in the Ti substrate. With increasing deposition duration, or decreasing plasma power and concentration of CH 4 in gas mixture, the compressive residual stress in the Diamond Coating decreased. The large residual stress in the Diamond Coating resulted in poor adhesion of the Coatings to substrate, but adhesion was also related to other factors, such as the thickness and nature of the TiC interlayer, etc. A graded interlayer design was proposed to lower the thermal stress, modify the interfacial structure and improve the adhesion strength.
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Effect of Plasma Power on the Deposition of Diamond Coatings on Pure Titanium
Materials and Manufacturing Processes, 2000Co-Authors: Bibo Van, Nee Lam Loh, Chang Q. SunAbstract:Abstract Diamond Coatings appear to be a promising solution for the improvement of tribological behavior of titanium alloys. By means of microwave plasma assisted chemical vapor deposition (MW-PACVD), Diamond Coating was deposited on pure titanium using CH4/H2 gas mixtures under different plasma powers. Surface and interface characterization of the deposited Coating under different plasma powers was carried out using SEM, grazing incidence x-ray diffraction (GIXD) and Raman spectroscopy. Adhesion of Diamond Coating with substrate was evaluated using an indentation tester. Results showed that adhesion of Diamond Coatings was not good under high plasma power, whereas the crystallinity of Diamond Coating was not good under low plasma power. The higher the plasma power, the larger the Diamond crystal size, the less content of non-Diamond carbon and the poorer the adhesion strength. During the Diamond deposition, growth of TiC competed with Diamond formation for the available carbon content. Relatively low pla...
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Characterization and tribological evaluation of MW-PACVD Diamond Coatings deposited on pure titanium
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: Bibo Yan, Chang Q. Sun, Nee Lam Loh, Peter HingAbstract:Titanium alloys are widely used in aerospace and biomedical conditions, however, they are notorious for the poor tribological properties. The deposition of a well adherent Diamond Coating is a promising way to solve this problem. In this study, Diamond Coatings were deposited on pure titanium using microwave plasma assisted chemical vapour deposition (MW-PACVD). Characterisation of Diamond Coatings was performed using scanning electron microscopy (SEM), laser profilometry, Raman spectroscopy, grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM). Tribological properties of Diamond Coatings were evaluated using a ball-on-disk wear tester (sliding with Al2O3 balls) and a scratch tester (sliding with Diamond pin). Results showed that the friction and wear properties of polycrystalline Diamond Coatings as well as the wear of the counterface were dependent significantly on the surface roughness, the morphology and crystalline structure of Diamond Coatings as well as the counterface materials. For (111)-textured Diamond Coatings with rough surface and sharp asperities sliding with Al2O3 balls, the coefficient of friction was much higher than that of (100)-textured Coatings, and the wear of the counterface material was quite high. After polishing the Diamond Coating, the surface roughness, coefficient of friction and wear of counterface decreased significantly. If sliding with Diamond pins, the coefficient of friction of Diamond Coating shows a quite low and stable value. To improve the tribological properties, a three-step deposition method was proposed to obtain a smooth and nano-crystalline Diamond layer on bulk Diamond Coatings. The so-formed Diamond Coating showed the highest load bearing capacity, the lowest coefficient of friction and the lowest wear of the counterface.
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Surface and interface characterization of Diamond Coatings deposited on pure titanium
Surface & Coatings Technology, 1999Co-Authors: Bibo Yan, Chang Q. Sun, Nee Lam Loh, Peter HingAbstract:Abstract Diamond Coatings appear to be a promising solution for the improvement of tribological behavior of titanium alloys. By means of microwave plasma assisted chemical vapor deposition (MW-PACVD), Diamond Coating has been deposited on pure titanium substrates using CH 4 /H 2 mixtures at moderate temperature (550–600°C). The surface and interface characterization of deposition Coating with increasing deposition duration up to 21 h has been studied using SEM and grazing incidence X-ray diffraction (GIXD). TiC formation on the substrate surface was detected after 15 min deposition. Growth of TiC competed with Diamond formation for the available carbon. The formation of a thick porous TiC layer appeared to promote interfacial debonding and spallation of the Diamond Coating. During the deposition of Diamond Coatings, hydrogen diffused into Ti substrate, and the formation of titanium hydride was detected by GIXD. The formation of TiC and Diamond layers did not inhibit the formation of titanium hydride. This led to profound microstructural changes and a severe loss of impact strength. A two-step process with higher ratio of CH 4 during the first step deposition appeared to be beneficial as a result of the higher nuclei density of Diamond crystals. The Diamond Coating so formed was observed to be in more intimate contact with the substrate.
Peter Hing - One of the best experts on this subject based on the ideXlab platform.
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Characterization and tribological evaluation of MW-PACVD Diamond Coatings deposited on pure titanium
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000Co-Authors: Bibo Yan, Chang Q. Sun, Nee Lam Loh, Peter HingAbstract:Titanium alloys are widely used in aerospace and biomedical conditions, however, they are notorious for the poor tribological properties. The deposition of a well adherent Diamond Coating is a promising way to solve this problem. In this study, Diamond Coatings were deposited on pure titanium using microwave plasma assisted chemical vapour deposition (MW-PACVD). Characterisation of Diamond Coatings was performed using scanning electron microscopy (SEM), laser profilometry, Raman spectroscopy, grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM). Tribological properties of Diamond Coatings were evaluated using a ball-on-disk wear tester (sliding with Al2O3 balls) and a scratch tester (sliding with Diamond pin). Results showed that the friction and wear properties of polycrystalline Diamond Coatings as well as the wear of the counterface were dependent significantly on the surface roughness, the morphology and crystalline structure of Diamond Coatings as well as the counterface materials. For (111)-textured Diamond Coatings with rough surface and sharp asperities sliding with Al2O3 balls, the coefficient of friction was much higher than that of (100)-textured Coatings, and the wear of the counterface material was quite high. After polishing the Diamond Coating, the surface roughness, coefficient of friction and wear of counterface decreased significantly. If sliding with Diamond pins, the coefficient of friction of Diamond Coating shows a quite low and stable value. To improve the tribological properties, a three-step deposition method was proposed to obtain a smooth and nano-crystalline Diamond layer on bulk Diamond Coatings. The so-formed Diamond Coating showed the highest load bearing capacity, the lowest coefficient of friction and the lowest wear of the counterface.
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Surface and interface characterization of Diamond Coatings deposited on pure titanium
Surface & Coatings Technology, 1999Co-Authors: Bibo Yan, Chang Q. Sun, Nee Lam Loh, Peter HingAbstract:Abstract Diamond Coatings appear to be a promising solution for the improvement of tribological behavior of titanium alloys. By means of microwave plasma assisted chemical vapor deposition (MW-PACVD), Diamond Coating has been deposited on pure titanium substrates using CH 4 /H 2 mixtures at moderate temperature (550–600°C). The surface and interface characterization of deposition Coating with increasing deposition duration up to 21 h has been studied using SEM and grazing incidence X-ray diffraction (GIXD). TiC formation on the substrate surface was detected after 15 min deposition. Growth of TiC competed with Diamond formation for the available carbon. The formation of a thick porous TiC layer appeared to promote interfacial debonding and spallation of the Diamond Coating. During the deposition of Diamond Coatings, hydrogen diffused into Ti substrate, and the formation of titanium hydride was detected by GIXD. The formation of TiC and Diamond layers did not inhibit the formation of titanium hydride. This led to profound microstructural changes and a severe loss of impact strength. A two-step process with higher ratio of CH 4 during the first step deposition appeared to be beneficial as a result of the higher nuclei density of Diamond crystals. The Diamond Coating so formed was observed to be in more intimate contact with the substrate.
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Deposition of Diamond Coating on pure titanium using micro-wave plasma assisted chemical vapor deposition
Journal of Materials Science, 1999Co-Authors: Yongqing Fu, Peter HingAbstract:The nucleation and growth of Diamond Coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH_4 and H_2 on the microstructure and mechanical properties of the deposited Diamond Coatings were evaluated. Results indicated that the nucleation and growth of Diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and Diamond nucleation; (3) growth of Diamond crystals and Coatings on TiC layer. During the deposition of Diamond Coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of Diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited Diamond Coatings. The effects of gas pressure and gas ratio of CH_4 and H_2 on the nucleation, growth and properties of Diamond Coatings were also studied. A higher ratio of CH_4 during deposition increased the nuclei density of Diamond crystals but resulted in a poor and cauliflower Coating morphology. A lower ratio of CH_4 in the gas mixture produced a high quality Diamond crystals, however, the nuclei density and the growth rate decreased dramatically.
Hiroyuki Hanyu - One of the best experts on this subject based on the ideXlab platform.
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the improvement of cutting performance in semi dry condition by the combination of dlc Coating and cvd smooth surface Diamond Coating
Surface & Coatings Technology, 2005Co-Authors: Hiroyuki Hanyu, Shoji Kamiya, Y Murakami, Y KondohAbstract:The authors have recently developed a finely crystallized smooth surface Diamond Coating. Using this Coating, the anti-sticking property of cutting tools was significantly improved in comparison to conventional rough surface Diamond Coatings. However, small crystal apices still remained. When aluminum alloy is cut by the tools with this Coating, small amount of aluminum alloy still sticks in the valleys in between the apices of Diamond crystals and causes friction loss. To solve this problem, we tried to apply DLC (Diamond like carbon) Coating over CVD Diamond Coatings on cutting tools. DLC Coating has very smooth surface and shows excellent performance in solid lubrication. But it does not have enough durability in the case being in contact with highly abrasive materials. On the other hand, the fine crystal Diamond Coating produced by the authors has great durability against highly abrasive materials. By putting them together, both the excellent lubrication performance and durability of Coating were compatibly achieved. These new combinations of Coatings lead to a better anti-sticking property of cutting tools for aluminum alloy and successfully increased the tool endurance.
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Dry and semi-dry machining using finely crystallized Diamond Coating cutting tools
Surface & Coatings Technology, 2003Co-Authors: Hiroyuki Hanyu, Y Murakami, S. Kamiya, Masumi SakaAbstract:Finely crystallized Diamond Coatings with smooth surfaces have recently been developed by the authors. In the present study, shaft tools with these new Coatings were applied to dry and semi-dry machining of highly adherent aluminum alloys whose efficient means of dry machining have not yet been established for. In comparison to the case of conventional Diamond Coatings with rough surfaces, more than four times longer durability of drills was realized in perfectly dry condition. In the case of minimum quantity of lubricant condition, the lifetime was found again to be more than four times longer and successfully achieved the largest improvement of Diamond-coated drills ever reported in semi-dry condition.
Danial Ghodsiyeh - One of the best experts on this subject based on the ideXlab platform.
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The Application of Surface Response Methodology to the Pretreatment of WC Substrates Prior to Diamond Coating
Journal of Materials Engineering and Performance, 2014Co-Authors: Mostafa R. Shirdar, Abolfazl Golshan, Sudin Izman, Danial GhodsiyehAbstract:High cobalt (Co) content greater than 10% in tungsten carbide is desirable because Co improves the toughness of the cutting tool. However, the additional Co poses a huge challenge in surface preparation given that the Co content must be reduced to less than 1% on the substrate surface prior to applying a Diamond Coating. The excessive presence of Co on the substrate surface during Coating suppresses Diamond nucleation and causes the deterioration of Diamond film adhesion. Many attempts have been made to overcome this issue, including the use of chemical etching, mechanical blasting, and heat treatment, but the successful pretreatment of WC-12%Co is still very limited. In this paper, a single-step chemical pretreatment using a mixture of sulfuric acid and hydrogen peroxide solutions was carried out on WC-12%Co. Two independent variables, i.e., etching time and acid temperature, were varied in the experiments to reduce Co contents as well as to roughen the substrate surface. The experimental plan was based on a central composite design. Variance analysis was employed to verify the precision of the mathematical models and their relative parameters. The predicted models generated by the response surface methodology (RSM) were compared with the experimental results, and close agreement was observed. The models demonstrated the significance of both factors, namely, acid temperature and etching time, in reducing Co contents to less than 1% as well as a roughening of the substrate surface within the desirable range.
Y Kondoh - One of the best experts on this subject based on the ideXlab platform.
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the improvement of cutting performance in semi dry condition by the combination of dlc Coating and cvd smooth surface Diamond Coating
Surface & Coatings Technology, 2005Co-Authors: Hiroyuki Hanyu, Shoji Kamiya, Y Murakami, Y KondohAbstract:The authors have recently developed a finely crystallized smooth surface Diamond Coating. Using this Coating, the anti-sticking property of cutting tools was significantly improved in comparison to conventional rough surface Diamond Coatings. However, small crystal apices still remained. When aluminum alloy is cut by the tools with this Coating, small amount of aluminum alloy still sticks in the valleys in between the apices of Diamond crystals and causes friction loss. To solve this problem, we tried to apply DLC (Diamond like carbon) Coating over CVD Diamond Coatings on cutting tools. DLC Coating has very smooth surface and shows excellent performance in solid lubrication. But it does not have enough durability in the case being in contact with highly abrasive materials. On the other hand, the fine crystal Diamond Coating produced by the authors has great durability against highly abrasive materials. By putting them together, both the excellent lubrication performance and durability of Coating were compatibly achieved. These new combinations of Coatings lead to a better anti-sticking property of cutting tools for aluminum alloy and successfully increased the tool endurance.