Wear resistance of a high nitrogen austenitic stainless steel coated with amorphous carbon films: influence of grain size and film composition

In this paper, the wear resistance of nitrogen alloyed austenitic stainless steels is, for the first time, investigated and compared to that measured for the same samples coated with amorphous carbon (a-C:H) films deposited by means of plasma enhanced chemical vapour deposition. Ball on Disk (BoD) tests are performed in order to investigate the wear stability of coated and uncoated substrates with different grain sizes. For the uncoated samples, the BoD results show a strong dependence of the wear track volume versus grain size. Furthermore, a strong improvement of the wear resistance is found in a-C:H coated specimens with respect to the uncoated ones with the same substrate microstructure. The effects of nitrogen incorporation into the films are also investigated showing an improvement of the tribological properties of the coated stainless steel. In particular, a synergic effect is detected between the grain refining and the film in the case of nitride amorphous carbon overcoats with a consequent increase of the wear resistance. (C) 2002 Published by Elsevier Science B.V.