The 3rd Malaysia-Japan Tribology Symposium, MJTS 2014, was held at Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia, on November 12-14, 2014. In MJTS 2014, 24 original papers were presented and 3 students were awarded “Excellent Student Research Awards.”Excellent papers presented were recommended for submission to Tribology Online and those have subsequently undergone the normal peer-review process by multiple reviewers and finally 6 papers were accepted and published in this Special Issue. On behalf of the Editorial Committee, I, the Guest Editor of Tribology Online, acknowledge the authors’ efforts to submit their papers to this Special Issue. I also express my sincere thanks to the Editors, the Reviewers, and the Publication Coordinators for their effort to complete the peer-review processes and the publication work.
The tribological behavior of diamond-like carbon films (DLC) is strongly dependent on the hydrogen content, sp2/sp3 ratio, and sliding environment. Some hydrogenated amorphous carbon films (a-C:H) exhibit superlow friction in hydrogen conditions. However, previous works have not clarified the dominant factors of the superlow friction phenomena of DLC films. In this research, we focused on the effects of hydrogen derived from the surrounding atmosphere and the hydrogen within the DLC films on superlow friction phenomena. To investigate these effects, friction tests were conducted on three DLC films having different hydrogen contents (0, and 18, 30 at%) in the air and in low-pressure-hydrogen conditions at various hydrogen pressures. After the friction tests, the wear tracks were examined by confocal laser scanning microscopy, Raman spectroscopy, elastic recoil detection (ERDA) analysis, and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The hydrogen derived from the surrounding atmosphere and the formation of the hydrogen-rich tribofilm were key factors for the superlow friction phenomena.
The wear particles generated from ultra-high molecular weight polyethylene (UHMWPE) are considered as the main reason to cause the osteolysis and aseptic loosening related to the failure of the artificial joint. This paper investigated the effect of radiation dose and contact pressure on the wear rate and wear particles of shelf-aged crosslinked UHMWPE using a multi-directional pin-on-plate wear tester. Scanning electron microscopy (SEM) and necessary software were used for quantitative analysis of wear particles. Results showed that for the shelf-aged crosslinked UHMWPE, the surface region where exhibited a low oxidation level, still maintained very good wear resistance. The specific wear rate was decreased with the increase of radiation dose and contact pressure. Quantitative analysis results of wear particles from crosslinked UHMWPE showed that after the wear tests, the percentage volume of smaller particles, complexity, specific biological activity (SBA) index of wear particles and the functional biological activity (FBA) index were reduced with increasing radiation dose. The contact pressure did not obviously affect the complexity of wear particles from crosslinked UHMWPE but had a clear influence on wear rate, SBA index and FBA index, and the effect on the particle size distribution was getting weaker as the radiation dose increases.
The aim of this study was to examine the mechanical characteristics of a polyvinyl alcohol hydrogel (PVA-H) as a candidate material for artificial joint cartilage. In the study, PVA-H was filled with α-tricalcium phosphate (α-TCP) in order to improve its mechanical properties. In addition, laminated composite materials with 3 layers were prepared by laminating α-TCP–filled PVA-H and unfilled PVA-H. The samples were prepared with different numbers of repeated freeze–thaw cycles and several concentrations of α-TCP. Compression tests and friction tests were carried out to investigate the mechanical and friction properties of the PVA-H. The results of the tests showed that the compressive modulus and the friction coefficient of the α-TCP–filled PVA-H were higher than those of the unfilled PVA-H. Thus, α-TCP was found to be effective in reinforcing the PVA-H. In the friction tests, the friction coefficient of the laminated material was approximately equal to the values of the unfilled PVA-H. Furthermore, the compressive moduli of the laminated materials that underwent 5 and 7 freeze–thaw cycles improved to a level equal to that of the α-TCP–filled PVA-Hs. Therefore, the lamination of PVA-H made it possible to achieve both a low friction coefficient and high compressive strength.
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 aim of this study was to investigate the effect of temperature on the tribological properties of Palm Kernel Activated Carbon-Epoxy (PKAC-E) composite. All specimens were formed into 10 mm diameter pins of 30 mm length, using a hot compaction technique. Tribological testing was carried out using a pin-on-disc tribometer in dry sliding conditions by applying temperatures in the range of 27°C to 150°C, at constant sliding speed, applied load, and sliding distance. The results showed that both coefficient of friction (COF) and wear rate of the composite increased with operating temperatures. Abrasive wear and crack formation that would induce delamination wear were identified as the predominant wear mechanisms.
Hardfacing layers developed by tungsten inert gas (TIG) surface melting on commercial purity titanium (CP-Ti) placing with a mixture of Fe, C and Si powders under two different traverse speeds (1 mm/s and 2 mm/s) and energy input of 1080 J/mm in an argon gas environment were investigated in terms of surface condition, microstructure, hardness and wear of the processed tracks. The surface appearance of treated layers was found to be free from any obvious defect. The TIG hardfacing layer produced dendritic structure due to dissolution of preplaced powder in the Ti melt. A maximum microhardness value of 630 HV0.5 was found on the surface layer processed with lower speed which was 2.5 to 3.5 times higher than the base material. Ball-on-plate wear tests exhibited better performance of the hardfacing layer than the untreated CP-Ti which is attributed to the presence of carbides and silicides in the Ti melt.