Methods for Determining Coating's Strength Properties Changes After Inducing Plastic or Elastic Residual Stresses

If the film of a coated part deforms plastically due to operational loads, residual stresses (RS) develop in the coating after the load removal. In this way, the film mechanical properties change induced by endogenous reasons, i.e. by the coating crystalline structure plastic deformation. Moreover, if only the substrate deforms plastically, the coating remains elastically deformed during the relaxation, due to the substrate RS. In this case, the film residual RS-changes are caused by exogenous parameters, i.e by the permanent substrate deformation. In the paper, novel experimental-analytical methods, based on nanoindentation and FEM calculations are introduced to determine film RS-changes, when the coating is deformed plastically as for example after micro-blasting, or elastically due to substrate plastic deformation as for instance after the ball penetration into the coated specimen during the impact test.