Investigation of combined surface treatments and coatings to increase the wear behavior of heat treatable steels

A combination treatment of nitriding and induction hardening can achieve high hardness depths in short treatment times and can therefore be seen as an alternative to deep nitriding. However, the compound layer, which makes a significant contribution to the wear resistance of nitrided components, decomposes during the induction heat treatment of the nitrided part. Therefore, the tribological behavior of parts processed this way is affected. In the present work, the wear behavior of surface layers resulting from combined heat treatment of EN42CrMo4 and PVD a-C:H(:Si) coating is investigated and evaluated. For the wear testing, a two-disk test rig was used. The wear was determined gravimetrically and by optical evaluation of the wear tracks. It was found, that the wear resistance of the investigated heat-treatable steel can be improved by duplex surface treatments such as nitriding and induction hardening as well as nitriding and PVD a-C:H(:Si) coating compared to the heat treated-only condition. By triplex treatment, no further improvement of the wear resistance could be observed.