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The purpose of this paper is to investigate the effect of multi-shape photochemical textured (PCT) steel surfaces on tribological performance. The textured surface with specific arrangement was fabricated by photochemical texturing, a common technique implemented in the microelectronic mechanical systems (MEMS) industry. It involves photolithography and chemical etching processes. The multi-shape studied were circle with line (CL) and circle with wavy (CW). Fabricated samples’ surfaces were characterized by using a 3D optical profiler to check the produced texture’s dimension. The effect of six different etching times on the texture’s dimension was observed. Then, only two sizes of both multi-shape textures were considered for tribological characterization. It was conducted by using ball-on-disk tribo-tester under lubricated conditions. The results obtained are compared with the reference untextured (UT) surface. From the results, it is found that appropriate size and shape of texture could lead to good friction reduction and anti-wear behaviour. The smaller size, size A, of CL multi-shape presented a lower friction coefficient compared to size B. However, different size of CW multi-shape has no effect on the friction behaviour. This is believed due to higher area density of CW compared to CL resulting in detrimental effect on friction for both CW’s size. Additionally, CL(size A) textured surface shows improved tribological behaviour compared to UT surface as lower friction coefficient and better wear resistance is obtained. This is maybe due to effective lubricating layer formation, good debris trapping effect and lower contact stress of the CL(size A) textured surface. These beneficial effects were achieved under lubricating condition through an increase in applied load.

Presence of adsorbed water on the solid surface gives significant influences on the tribological phenomena. This study aims to elucidate how the difference in surface roughness of austenitic stainless steel influences the amount of adsorbed water. Firstly, the necessary time for the adsorbed water to saturate on the surfaces with different roughness when relative humidity (RH) changed was determined by weighing method. Then, the saturated adsorbed water amount at different RH % was determined for the surfaces with different roughness. It was clarified that the rougher surfaces tend to require longer time for water adsorption to achieve the saturation level and adsorb more amount of water compared with smoother surfaces.

Hard anodizing has proven to be a helpful surface treatment for aluminium alloy and typically accompanied by the growth of a porous and highly flawed oxide layer. The presence of pores on the oxide surface can be taken as an advantage in improving the surface properties. Fly-ash particles are high in SiO2 and Al2O3 content and can be utilized as inexpensive strengthening particles, which can increase the wear resistance and microhardness of composite material. It was noticed that limited research had been carried out in utilizing fly-ash as reinforcement on composite oxide coating as a wear resistance candidate. Thus, this study focused on reinforcing fly-ash on oxide coating and investigating its tribological performance. The composite oxide coating was grown on AA2017 aluminium alloy through anodizing process. To understand the effect of anodizing time and fly-ash content, the parameters were varied from 5–60 min and 0–50 g/L, respectively. The findings suggested that 60 min of anodizing time provides the highest thickness and surface roughness at 35 µm and 6.5 µm, respectively. Interestingly, composite oxide coating with 50 g/L fly-ash provides the highest coating thickness but has the lowest roughness at 52 μm and 8.2 μm, respectively. The composite oxide coatings are observed to reduce friction only for a limited time, despite their potential in significantly reducing the wear rate. The wear mechanism observed was adhesion, micro-crack, and delamination. The findings of this study are believed to provide insight on the potential of fly-ash to be a reinforcement for wear-reduction materials.

The study of the effect of humidity on friction behavior in HiPIMS (High Power Impulse Magnetron Sputtering) W-C:H coating/steel ball system confirmed the formation of transfer layer adhered to the ball and consisting of hydrogenated carbon, ferritungstate and small amounts of tungsten (sub)oxides and iron oxides. The corresponding mechano(tribo)chemical reactions driven by flash temperature in the sliding asperities involved oxidation, water vapor dissociation and carbon hydrogenation. Such composition agreed with the results of modelling based on the minimization of free Gibbs energy in the mutually interacting thermochemical reactions. The applicability of modelling to friction was attributed to fast reactions among microscopic asperities eliminating kinetical factors. In inert atmospheres, oxidation and hydrogenation were suppressed and friction seemed to be controlled by the amount of additional carbon.

A physical model of adhesive wear mechanism needs to be improved from quantitative aspect as possible to predict phenomena in the real world. The model should also be able to provide necessary information for the design of tribo-mechanics in logical manner. In this research, an attempt on explaining how saw teeth shape in the chart of specimen displacement perpendicular to the sliding surface for tribo-testing of adhesive wear using a quantitative simulation method had been made. Some simple processes i.e. sliding, accumulation of material and transfer of the accumulated material, which appear in the very early stage of sliding, are subjects of simulation in this research. A simple model which consisted of limited number of parameters could achieve success to simulate experimental data to some extent and mimicked the selected simple processes. The research clarified the limitation of the proposed model. Necessary additional parameters should be shape and size of a transfer unit and shear strength at interface of sliding with theoretical background. It is necessary to define those parameters theoretically based on scientific knowledge to comprehend the sliding phenomena.

A study was carried out on the influences of atmospheric humidity in the very early stage of sliding for austenitic stainless steel (JIS SUS316). Pin-on-disk tests were conducted under different rates of relative humidity (RH). A relatively low magnitude of applied load to lessen the influences of mechanical effect was employed for emphasizing the humidity effect on tribological phenomena. The results of the current study were compared with our previous study results obtained at higher magnitude of applied load. The comparison suggested different mechanisms of adsorbed water layer exert influences on the tribological phenomena in the very early stage of the sliding when applied load was changed.

The authors have been developing objective and combinational analysis method for multiple kinds of data obtained by a repeated sliding test performed with a pin-on-disk apparatus to clarify the wear mechanisms. The developed analysis method successfully showed the growth rate and the size of adhered substances on the sliding surface for adhesive wear mechanism. In this paper, the developed method was applied for analyzing chronological changes in severe-mild wear forms transition to understand the phenomena more quantitatively. Friction force, pin specimen displacement perpendicular to the slid surface and electrical contact resistance between pin and disk specimens were employed as the multiple kinds of data. The devised analysis showed that the formation of a plateau with around 25 μm height on the slid surface is a key factor for the transition.

A study was carried out to estimate the thickness of the adsorbed water layer on the surface of austenitic stainless steel (JIS SUS316) in different atmospheric humidity conditions. The purpose of the study is to have a quantitative data on water adsorption that has influences on the tribological phenomena. The mass of stainless steel plate was determined by the weighting method as a function of the relative humidity (RH) in ambient atmospheric air. An experimental device consisting of atmospheric humidity controller and high sensitivity analytical balance with affixed airtight chamber was used for the purpose of the study. The result of water adsorption progression on SUS316 surface has been discussed and schematically demonstrated. It is clarified that the thickness of adsorbed water is significantly large to influence the tribological properties as demonstrated in a schematic model of the interface state of pin-on-disk prior to contact in high RH.

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.

The influences caused by difference in relative humidity (RH) on the early stage of dry sliding were studied using a horizontal ball-on-disc tribotester equipped with air-humidity controller. The ball displacement perpendicular to sliding surface and friction force during the initial stage resulted in different consequences with different percentage of RH. The middle rate of RH 49% showed a contradictory behavior with the common sense known that friction force of sliding decreases with increment of RH. Friction force of sliding can be dominated by water meniscus and water viscosity as well as local solid-solid contact in atmosphere at certain rate of RH.

The influence of trace water and oxygen in a hydrogen environment on the sliding behavior of pure iron was studied using a newly developed pin-on-disk apparatus in a vacuum chamber equipped with an advanced gas replacement system. The hydrogen environment in the siding tests contained 0.5 to 95 ppm water and 0.07 to 2 ppm oxygen; a turbo-molecular pump was used for evacuation and a chemical filter for reducing water and oxygen in the hydrogen gas supplied to the chamber. The concentrations of water and oxygen in the hydrogen overflow from the chamber were determined using moisture and oxygen sensors, respectively. Other potential contaminant gases were analyzed using a quadrupole mass spectrometer during evacuation and were found to be insignificant. The amount of wear and the appearance of wear debris as well as the sliding surfaces were significantly different for the different concentrations of water and oxygen. The roles of these gasses are discussed.

A new tribo experiment system is developed for sliding tests under high purity gas environments including hydrogen. It uses a transfer vessel such that surface oxidation does not substantially occur during transfer of specimens to surface analyzers. The system’s seal ability is confirmed with surface analysis with XPS and sliding tests with stainless steel. It is found that oxidation as well as adsorption of hydrocarbons as contaminants on steel surfaces during transfer is prevented. In the sliding test, differences in oxide formation on steel surfaces in hydrogen, in vacuum and in air are detected clearly.

The author proposed a new analysis method to conjecture friction and wear mechanisms for the repeated sliding test performed with a pin-on-disk apparatus. Two kinds of data, friction force and pin displacement perpendicular to the sliding surface, were analyzed to obtain a frequency distribution chart of the combinations of these two kinds of data. The devised analysis method was applied to data obtained in adhesive and abrasive wear systems to verify its function. The method successfully differentiated these two sliding systems, and detailed time dependent changes of each system were described.

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.

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 © 2011 by ASME

Ti(C, N) films have been deposited by reactive ion plating and their tribological behavior against steel in air and in argon atmosphere was characterized. It was very effective to decrease wear rate of steel to coat Ti(C, N). The influence of atmosphere on wear of the Ti(C, N) coatings was studied in the dry sliding of steel pin using a pin-on-disk configuration. The wear rate in air was lower than that in argon atmosphere. The decrease of the sliding wear of the steel disk by applying the Ti(C, N) coating was due to formation and growth of iron-oxide particles on the surface of the coating and high shear strength of the coating. A lot of fine and thin iron-oxides were observed at the sliding surface of the Ti(C, N) coating in air and they were identified as magnetite (Fe3O4). It is suggested that small iron debris is derived from pin and oxidized by the reaction with oxygen in air and a protective oxide particle can be formed by growth of oxide debris. These oxides are considered to insulate steel substrate from steel pin, resulting in decreasing adhesive force between pin and disk. Wear behavior of the Ti(C, N) coatings by changing atmosphere is discussed in comparison with a case of steel pair.

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 © 2010 by ASME

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 © 2010 by ASME

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 © 2008 by ASME

Discs of typical engineering ceramics such as silicon carbide, alumina, zirconia and SiAlON were tested in the ball-on-disc type rolling contact fatigue mode using steel balls under lubricated conditions. The fatigue life of the ceramics increased in the order described above. By calculating the maximum tensile stress generated on the edge of a Hertzian contact area in the ceramic discs and comparing with the inherent strength of the material, it was possible to estimate whether the fracture mode depends on the Hertzian cracks or not. Although the cracks occurred in silicon carbide and alumina, no Hertzian cracks appeared in SiAlON materials in both the pressureless sintered and HIPed states for a stress level of 5.88GPa. It is also clarified that HIP treatment improves the fatigue life two orders of magnitude.

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

Understanding the sliding phenomena based on fundamental mechanisms is indispensable to improve the stability and expected life time of sliding parts which work in industrial field. In this paper, adhesive wear in a repeated sliding system was analyzed with a newly devised pin-on-disk apparatus. The analysis on time series data showed some correlational relationship between wear particle sizes and specimen displacement perpendicular to the sliding surface.