Kanao Fukuda

Sliding Properties of Pure Metals in Hydrogen Environment

As the first step to understand how hydrogen influences the sliding properties of metallic materials, nine self-mated pairs of metallic elements were tested using a pin-on-disk apparatus. The results of friction force, wear amount, and observations of wear debris showed that the elements could be roughly categorized into two groups; transition and non-transition elements. Chemisorption of hydrogen on the sliding surfaces was thought to be predominant of the tribological properties in the first group of elements, while chemisorption did not take place on the sliding surfaces of the latter group. The effect of hydrogen on sliding appeared similar to that of oxygen in terms of chemisorption.Copyright

An Investigation of Lapping Characteristics for Mirror-Like Finish Using a Lathe with Linear Motor

Lapping is possible to produce excellent surface finish with higher geometrical form. Additionally, automated lapping process is perfectly suited with todays industry requirements and also economically advantage over other manufacturing processes. This research is devoted to study the characteristics of the lapping process for mirror-like surface finishing by using the linear motor lathe. In the process of mirror-like finish, various factors that effect on rate of material removal, limit surface roughness and geometrical form improvement were examined on low, medium and high hardness materials by series of experiments. The conclusion shows that active grain characteristics, hardness ratio, lapping pressure, lapping speed, residual stress and chatter vibration on the work surfaces all have influenced on the mirror-like surface finishing process.

Influences of Trace Water in Hydrogen and Argon on the Tribological Properties of Pure Iron

Tribological properties of pure iron were studied in argon environments containing trace water which is controlled at the value between 1 and 10,000 ppb and virtually no oxygen. The experimental data were compared with those obtained in our previous study with the same conditions of experiment but in hydrogen. The influences of trace water were recognized in both gases and confirmed not peculiar to a hydrogen environment. The coefficients of friction and specific wear rates were different to some extent between argon and hydrogen environments. The differences were supposed to be attributed to the influences of hydrogen atoms which chemisorbed on pure iron atoms appeared on the nascent surface made by sliding. Whether hydrogen and water have synergy effect on influencing tribological properties was not clarified in this study.

Influences of gases on the tribological properties of pure iron

In this study, trace oxygen and water as impurities in experimental gas environments were reduced to less than 10 ppb to eliminate their influences on the tribological properties. A pin-on-disk apparatus in an ultra-high vacuum vessel equipped with a gas filtering system enabled pure experimental gas environments. Dry friction tests clarified that the tribological properties of pure iron in ultra-high vacuum and argon were similar to each other. On the other hand, friction coefficients obtained in hydrogen and nitrogen were considerably lower than those obtained in ultra-high vacuum and argon. Specific wear rates of pin and disk were close to each other in ultra-high vacuum, argon and hydrogen while those took very different values in nitrogen. Hydrogen influenced the tribological properties of pure iron to some extent but the influences were not as much as that of nitrogen.Copyright

Tribological Properties of Austenitic Stainless Steel in Pressurized Hydrogen Up to 40 MPa

The tribological properties of austenitic stainless steel (JIS SUS316L) were studied in pressurized hydrogen, i.e. 0.3, 10 and 40 MPa. The coefficient of friction was small under all the conditions tested in this study by comparison with data obtained previously at the standard hydrogen pressure (0.1MPa). The specific wear rates decreased with an increase in the atmospheric hydrogen pressure.Copyright

Tribological Characterization of Polymeric Sealing Materials in High Pressure Hydrogen Gas

Bearings and seals used in fuel cell vehicles and related hydrogen infrastructures are operating in pressurized gaseous hydrogen. However, there is a paucity of available data about the friction and wear behavior of materials in high pressure hydrogen gas. In this study, authors developed a pin-on-disk type apparatus enclosed in a high pressure vessel and characterized tribological behavior of polymeric sealing materials, such as polytetrafluoroethylene (PTFE) based composites, in gaseous hydrogen pressurized up to 40 MPa. As a result, the friction coefficient between graphite filled PTFE and austenitic stainless steel in 40 MPa hydrogen gas became lower compared with the friction in helium gas at the same pressure. The chemical composition of worn surfaces was analyzed by using X-ray photoelectron spectrometer (XPS) after the wear test. Results of the chemical analysis indicated that there were several differences in chemical compositions of polymer transfer film formed on the stainless disk surface between high pressure hydrogen environment and high pressure helium environment. In addition, the reduction of surface oxide layer of stainless steel was more significant in high pressure hydrogen gas. These particular effects of the pressurized hydrogen gas on the chemical condition of sliding surfaces might be responsible for the tribological characteristics in the high pressure hydrogen environment.Copyright

Tribology of Ceramic Matrix Composites against Metals

Abstract The sliding of silicon nitride matrix–silicon carbide whisker composites against bearing steel has been investigated, and it was observed that the wear of the ceramic specimens decreased with increasing amount of incorporated whiskers. In hot-pressed silicon nitride based ceramics, the appearance of anisotropy in the mechanical properties has generally been observed. Such an anisotropy was also found in the tribological properties of those ceramics. A series of investigations on ceramics sliding against pure iron was also carried out, with as result that composite ceramics did not always show better wear resistance than monolithic ones. The tribological compatibility must be considered with first priority when the sliding countermaterial is selected. In this chapter, the discussion is based on the viewpoint of the adhesive-wear mechanism with special emphasis on the tribological compatibility of the sliding materials