Papers by Author: Shinya Sasaki

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Authors: A. Iwase, T. Iwata, T. Nihira, Shinya Sasaki
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Authors: Jia Hu Ouyang, Takashi Murakami, Shinya Sasaki, Yu Zhou
Abstract: The friction and wear characteristics of a cathodic arc ion-plated CrSiN coating in sliding against different counter materials have been investigated under both unlubricated and boundary-lubricated conditions. Under boundary-lubricated conditions, the CrSiN coating exhibits a friction coefficient of 0.12 to 0.20 against a SAE 52100 steel ball and of 0.04 to 0.07 against a CrN-coated steel pin, depending on wear parameters used. The effects of load, temperature and counter materials on friction and wear of the CrSiN coating were discussed. The worn surfaces and wear debris generated under different wear conditions were examined by means of scanning electron microscopy and Raman spectroscopy to identify the tribochemical reaction and phase structures generated during the wear process. Under unlubricated conditions, iron-based oxides formed in sliding against a steel ball, while some chromium oxides were identified on worn surfaces of the CrSiN coating in sliding against an alumina ball in air.
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Authors: Jia Hu Ouyang, Takashi Murakami, Shinya Sasaki, Yu Feng Li, Ya Ming Wang, K. Umeda, Yu Zhou
Abstract: The high-temperature friction and wear characteristics of different ceramics and ceramic matrix composites (CMCs) incorporated with various solid lubricants have been investigated from room temper- ature to 1000oC. The solid lubricants considered in this paper include representative precious metals, hexagonal boron nitride, graphite, fluorides, soft oxides, chromates, sulfates, and combinations of various solid lubricants. General design considerations relevant to solid lubrication were proposed on the basis of friction and wear data of self-lubricating CMCs. The self-lubricating composites incorporated with SrSO4 or/and CaSiO3 exhibits low and stable friction coefficients of 0.2 to 0.3 and small wear rates in the order of 10-6 mm3/Nm from room temperature to 800oC. The optimized composites appear to be promising can- didates for long-duration, extreme environment applications with low friction and small wear rate.
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Authors: Takashi Murakami, K. Umeda, Shinya Sasaki, Jia Hu Ouyang
Abstract: In the present study, Al2O3, (ZrO2-3mol% Y2O3)-39.6mass% Al2O3, Si3N4 and MgO substrates coated with SrSO4 particles were prepared, and their high-temperature tribological properties were investigated. It was clarified that SrSO4 worked as solid lubricant efficiently against Al2O3 and (ZrO2-3mol% Y2O3)-39.6mass% Al2O3 substrates in the temperature range of room temperature to 1073K in air. In addition, thin SrSO4 films were observed on the wear scars formed on the Al2O3 and (ZrO2-3mol% Y2O3)-39.6mass% Al2O3 substrates.
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Authors: Takeshi Murakami, Shinya Sasaki, K. Ito, Haruyuki Inui, Masaharu Yamaguchi
2557
Authors: Jia Hu Ouyang, Takashi Murakami, Shinya Sasaki, Yu Zhou, De Chang Jia, Ya Ming Wang
Abstract: Spark plasma sintering is employed to synthesize a variety of self-lubricating ZrO2(Y2O3)- Al2O3 matrix nanocomposites by tailoring the chemical compositions and by adjusting the sintering parameters. Different additives are incorporated into the nanocrystalline ceramics of ZrO2(Y2O3)- 20wt.% Al2O3 to evaluate their potentials as effective high temperature solid lubricants from room temperature to 800oC by using a high temperature friction and wear tester in sliding against alumina ball in air. The density, microstructure, hardness and tribological properties of the sintered nanocomposites have been investigated, as contrasted with the unmodified ceramics, to obtain a better understanding of lubrication mechanisms over a wide temperature range. The ZrO2(Y2O3)-Al2O3-SrSO4 composite exhibits steady-state friction coefficients of less than 0.2 and wear rates in the order of 10-6 mm3/Nm over a broad temperature range from room temperature to 800oC.
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Authors: Yan Qiu Xia, Shinya Sasaki, Takashi Murakami, Miki Nakano
Abstract: The friction and wear properties of phosphor bronze discs sliding against SAE52100 steel balls were evaluated using an Optimol SRV reciprocating friction and wear tester under the lubrication of pure poly-alpha-olefin (PAO) and PAO containing commercial phosphite ester, zinc dialkyldithiophosphate (ZDTP) and oleic acid additives. The morphologies of the worn surfaces of the phosphor bronze discs were observed using a scanning electron microscope (SEM). In addition, the elemental compositions and chemical states of several typical elements on the worn surfaces of the phosphor bronze discs were examined by means of X-ray photoelectron spectroscopy (XPS). The findings indicated that the phosphor bronze discs exhibited higher wear resistance under the lubrication of PAO containing phosphite ester than pure PAO, PAO containing ZDTP, and PAO containing oleic acid. Also, the phosphor bronze discs exhibited stable friction coefficients as low as 0.09-0.11 when lubricated with PAO containing phosphite ester. According to the XPS analyses, it was considered that the formation of CuO and phosphate led to lower friction coefficient and high wear resistance of phosphor bronze specimens lubricated with PAO containing phosphite ester. In the case of the phosphor bronze specimens lubricated with PAO containing ZDTP and oleic acid, the formation of organic compounds seemed to lead to lower friction coefficient, but did not seem to affect the wear resistance.
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Authors: Takashi Murakami, T. Inoue, H. Shimura, Shinya Sasaki, Miki Nakano
Abstract: In this study, Fe-2.0Si-4.6C (mass%) gray cast iron disk specimens with three different matrix phases were coated with MoS2 using pressure spraying, and the friction and wear properties of the specimens were investigated against AISI52100 steel and polytetrafluoroethylene balls under the lubrication of oil using an Optimol SRV friction tester. When AISI52100 steel balls were used as the paired material, all of the MoS2-coated gray cast iron specimens showed lower friction coefficients and higher wear resistance than the non-coated disk specimens. On the other hand, MoS2-coated gray cast iron specimens exhibited higher friction coefficients than non-coated disk specimens for the most part, when polytetrafluoroethylene balls were used as the paired material.
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