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this paper, the adhesive wear characterization of MoS2, PTFE and mixture of MoS2 and PTFE films coated on stainless steel substrate, i.e. SUS440C, have been studied. The films were deposited by dry spray techniquecommercially available domestically. The films properties which are surface hardness, film thickness, surface roughness and adhesion strength were investigated. The thickness and the surface hardness of the films were approx. 7, 6.8 and 6.2 µm and 0.1,0,8 and 0.4GPa for MoS2, PTFE and the mixture of MoS2 and PTFE, respectively.The surface roughness of MoS2, PTFEwerefound to be similar with the value of Ra of approx. 0.302-0.303 µm. The mixture of MoS2 and PTFE showed smoother surface with the surface roughness (Ra) of approx.0.260µm. The PTFE film has shown better adhesion strength with higher critical load for first failure and full delamination. However, the failure pattern observed suggested lower severity of surface damage.Theresults fromtribologicaltests between the coated SUS440C ball and the SUS304 discshowedstrong effect of the coating on adhesive wear behavior of the contacting systems.For MoS2coated surface, the coatingsurface peeled offgraduallyuntil the surface ofthe substrate was revealed. Whereas, the PTFEcoated surface had delaminated immediately once in contact resulting in plate liked wear debris.The mixture ofMoS2 andPTFE haslower thefriction coefficient compared to the individual coating. Thewearbehavior found on the mixture of MoS2 and PTFE coated surface had similar characteristic to those found on surfacecoatingwithMoS2. It also showed lower wear occurrences with better appearance due to tearing wearat the edges of the worn suggesting better load capacity of the mixed film than the individual PTFE coating.

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Ti-based coating has been used for biomaterials to improve biocompatibility, mechanical and corrosion properties. Each coating shows unique performance depending on a variety of factors such as coating microstructure and properties as well as in-service conditions. In this study, the microstructure, surface topography, hardness, adhesion and corrosion properties of Ti and TiN films on stainless steel 316L coated by cathodic arc physical vapor deposition process (PVD) were studied. The results showed that the surface roughness of 316L increased after being coated with Ti and TiN film as evidenced by the numerous particles and voids observed on the surface of both films. The hardness of 316L coated with Ti and TiN was increased by approximately 50% and 85%, respectively. Ti and TiN coated samples showed good adhesion strength with the first critical load (LC1) of approximately 10N and 15N, respectively. However, the types of film failure for Ti and TiN were found to be different. Partial delamination with a high degree of plastic deformation was observed for Ti coating, whereas surface cracks were found for TiN coating. This finding is likely attributable to the difference in flow resistance and the amount of particles and voids observed. All samples showed a stable passive region during 7 days of immersion in Ringer’s solution. Ti film showed better corrosion resistance than TiN, which may have been caused by the effect of more voids on TiN surfaces formed by PVD coating.

In this study, the effect of deep cryogenic treatment on the generation of stainless steel particles in screw tightening process in hard disc drive assembly was investigated. During the cryogenic treatment, the specimens of both stainless steel screw and contacting tool (called as “bit”) material were quenched in a chamber containing liquid nitrogen at-196 oC with the soaking times of 33 hr. The specimens were then subjected to sliding wear tests under normal loading conditions. The experiments used for simulating dry sliding wear mechanisms were carried out by TriboGear machine. The machine consists of a stationary bit loaded against the plate containing screw. The screws used were made of martensitic 410 stainless steel and the bit was made of S2 tool steel. The experiments were carried out under both under single and multiple loading cycles under the normal load corresponding to the effective stresses higher and lower than the yield strength of screw material. The results showed that the deep cryogenic treatment led to more homogeneous distribution of fine size carbide particles in both martensitic 410 stainless steel and S2 tool steel. This lead to different failure mechanism of the stainless steel resulting in smaller and slender stainless steel particles generated. This was expected due to the effect of the change in the dimension of carbide, the stress distribution in the material and the crack propagation path.