The sliding friction between solids is a problem related to the material surface and its neighborhood. It is very important to control and adjust it in engineering. In this research, the characteristics of sliding friction between thermal sprayed surfaces have been studied. Materials sprayed were aluminum (Al), zinc-5% aluminum alloy (Zn-A1), and alumina (Al2O3) and sliding pairs were either of the same material or of different materials. Further, it also has been studied from the standpoint of applying thermal spraying to the surface treatment for high-strength bolted joints. In the experiments, frictional force was recorded as a function of sliding distance. It was found that force-distance curves of as-coated specimens could be classified into two types; one is periodical oscillation with the stick-slip such as for the sliding pair of Zn-Al/Zn-Al and the other is with random fluctuation for the sliding pairs of Al/Al and Al2O3/Al2O3. The coefficient of friction was biggest for sliding pair of Al/Al, which is about 2 times as high as that of the shot-blasted surface of mild steel substrate (for Al/Al and Zn-Al/Zn-Al). It has been confirmed also that Amontons law is applicable in any of the sprayed sliding pairs tested. Especially, it has be shown that aluminum-sprayed coating and zinc-sprayed coating will be expected to apply to high-strength bolted joints, because of having big coefficient of friction and strong corrosion resistivity.
