Carbon-based films such as diamond, diamond-like carbon, and carbon nitride exhibit a low coefficient of friction in the order of 0.1 or an ultra-low coefficient of friction in the order of 0.01. In addition, depending on the friction conditions, they may exhibit a high friction coefficient of 0.3 or higher. However, there are no reports explaining why carbon-based films exhibit these properties. To address this issue, the factors involved in the development of low friction coefficients in carbon-based films in dry environments are considered in this study, and eight phenomena are proposed. The basic concept is that a carbon-based film is graphitized by frictional heat in the presence of trace amounts of oxygen and/or water; which results in the generation of gases such as CO, CO2, H2, and N2, further reducing its friction coefficient. Consequently, it was possible to reasonably interpret the various frictional properties of carbon-based films, and to clarify the relationship between conditions such as the atmosphere of friction and friction properties, in relation to these eight phenomena.
This study developed surface finishing methods to prevent corrosion of electropolished SUS316L stainless steel in isopropyl alcohol（IPA）. For this development, immersion corrosion tests in 99.7% IPA and anodic polarization tests in 0.15 kmol･m－3 HCl were conducted using electropolished SUS316L specimens passivated with 30% HNO3, 0.1 kmol･m－3 Na2MoO4-containing 30% HNO3, 3.5% H2O2 and 0.98% H2O2- containing 8% citric acid. Identical tests were also applied to specimens heated to 200－450 ℃ after passivation treatments. Corrosion morphologies of these specimens in 99.7% IPA exhibited pitting. Pit densities and corrosion rates of these specimens in 99.7% IPA showed good correlation with pitting potentials in 0.15 kmol･m－3 HCl. Judging from the obtained values of pit densities and pitting potentials, specimens passivated with 30% HNO3 or 0.1 kmol･m－3 Na2MoO4-containing 30% HNO3 showed very good corrosion resistance against IPA corrosion. Heat-treatment at 200 ℃ after surface finishing using 30% HNO3 and 0.1 kmol･m－3 Na2MoO4-containing 30% HNO3 increased corrosion resistance against IPA. However, heat-treatment at temperatures higher than 350 ℃ decreased the corrosion resistance.