Comparison of reciprocating wear behaviour of electrolytic hard chrome and arc-PVD CrN coatings

This study was conducted to systematically investigate the wear behaviour of electrolytic hard chrome and arc-PVD coatings under lubricated reciprocating conditions. Experiments were conducted in unformulated base oil and the effects of normal load (5, 10 and 30 N) and temperature (room and 60 °C) on wear behaviour of both electrolytic hard chrome and arc-PVD CrN coatings are investigated. The results indicated that CrN performed better than hard chrome plating under lubricated reciprocating wear conditions used in this study. This effect became more pronounced by the increase of temperature and normal load. Profilometric wear depths on both coatings could not be determined after the tests conducted at room temperature. However, at 60 °C, wear depths as deep as 3.5 μm (at 30 N load) on EHC coating could be recorded by profilometer. Profilometric depth on CrN coated discs could not be detected. The reciprocating sliding tests on brushed CrN coated discs clearly demonstrated the important role of droplets on tribological behaviour of arc-PVD coatings.