Effects of oxide layer on the friction characteristics between TiN coated ball and steel disk in dry sliding

In this study, the effect of oxide layer on friction characteristic of titanium nitride (TiN) coated ball and steel disk was investigated through sliding test. Sliding tests were conducted in both air and nitrogen environments to study the role of oxide layer in sliding motion as well as to investigate the effect of oxide layer on TiN coating. For the coated ball specimen, AISI52100 steel ball was used and AISI1045 steel was used for the disk type counter part. From the results, the iron oxide layer, which is formed by the adhesive wear, formed on wear track in the steel disk dominates the friction characteristics between the two materials and induces friction transition and high friction. The oxide layer on the coated ball delays the oxide layer formation on the disk. Therefore, the low friction region increases as the iron oxide amount on coated ball increases, but it does not induce friction transition and high friction. And the oxide layer formed on steel disk in air can be removed by wear in nitrogen environment and because of that, the low friction region reappears.