Influence of Sliding Speed and Surface Roughness on the Friction Coefficient and Wear of TiN Coatings Deposited at Low Temperature

Abstract

Wear behavior of TiN coatings during dry reciprocating sliding against an alumina ball was studied. The research focus was on the influence of sliding speed on friction and wear. In addition, the coatings of different surface roughness were tested in order to find the optimum one. The range of surface roughness analyzed in this research provides insight into a rarely studied domain of fine surface finish. The wear tests were conducted at low load with low sliding speeds in order to determine the wear behavior of TiN coatings in mild conditions. Low values of friction coefficient were obtained, ranging from 0.13 to 0.24. The decreasing trend of the friction coefficient and increasing trend of the wear rate with increase in the sliding speed were observed for the coatings of different surface roughness. The highest friction coefficient was found on the roughest specimen, while the smoothest specimen exhibited the highest wear rate. The different wear behavior is due to different wear mechanisms acting on specimens with different roughness. For the tests conditions and range of surface roughness studied, the coating with roughness of 20 nm has the optimum surface finish. This coating exhibited low friction coefficient and the lowest wear rate. No significant difference in wear behavior was found when sliding transversal and parallel to machining ridges.