Papers by Author: Miki Nakano

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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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