Residual stresses and residual stress distributions in TiCN- and TiN-coated steels

Abstract

In this paper results are presented using X-ray diffraction for the analysis of residual stress states in hard coatings formed by chemical vapour deposition (CVD) and physical vapour deposition (PVD). The problem of the unknown X-ray elastic constants was solved by measuring these constants for CVD TiCN and PVD TiN coatings on steel 52100 for different coating temperatures and different X-rays (Cr Kα and Cu Kα). Using the measured constants residual stress states at the surface as well as depth profiles of residual stresses in the coatings and the substrate were determined.CVD TiCN coatings exhibited compressive residual stresses, depending strongly on the temperature of the coating process and on the substrate material used. For the TiN coatings the temperature dependence of residual stresses is strong for specimens coated on a single side and less for specimens coated on two sides. Surface residual stresses increased to very high values with increasing substrate bias. Residual stress distributions exhibited practically constant values of the residual stresses over the coating thickness. At the interface differences between the CVD and PVD processes were found.