A novel criterion to identify coatings’ adhesion

A novel criterion, plastic/elastic deformation work (Wp/We), was introduced to identify the co-deformation capacity of chromium–nitrogen (Cr–N) coating and titanium alloy system, which can be related to the coating/substrate adhesion. By changing the N2 flow (fN2), the Cr–N coatings were deposited on Ti6Al4V (TC4) alloy substrate to obtain Cr(N), Cr2N and/or CrN coatings, which could be related to the various deformation capacities. It indicated that the high Wp/We ratios of the metallic Cr(N)/TC4 systems deformed coordinately and attached well. Among the ceramic CrNx/TC4 systems, the single-phase CrN/TC4 exhibited higher Wp/We ratio of 1.71 than 1.52 and 1.61 of the Cr2N or Cr2N@CrN/TC4 and better adhesion. As a novel criterion, Wp/We ratio indicates the co-deformation capacity of a coating/alloy system, related to the failure mechanism and the adhesion of a coating to the substrate.