Comparative Study on the Mechanical Properties and Thermal Stability of Cr/Cr–N Multilayer Coatings with Different Phase Structures

Cr–N coatings are promising for severe-service applications owing to their high corrosion and wear resistance, yet their performance is governed by phase constitution and multilayer architecture. In this study, a monolithic Cr coating and three Cr-based multilayer coatings, Cr/Cr(N), Cr/Cr2N, and Cr/CrN, were synthesized by a hybrid DCMS/HiPIMS process and systematically compared with respect to structure, mechanical properties, and oxidation behavior at 900 °C. XRD and TEM showed that Cr/Cr(N) was primarily characterized by a bcc Cr-type structure, while the N-containing layers exhibited slightly expanded lattice spacings relative to pure Cr; no Cr2N precipitates were detected within the resolution of the analyses. Among the multilayers, Cr/Cr(N) provided the most favorable combination of hardness, adhesion, and indentation damage tolerance, reaching 885 HV and a critical scratch load of 80 N while maintaining damage tolerance comparable to monolithic Cr. By contrast, Cr/Cr2N and Cr/CrN displayed more pronounced brittle damage and lower interfacial reliability. Upon oxidation at 900 °C, Cr and Cr/Cr(N) formed relatively compact Cr2O3 scales, whereas Cr/Cr2N, and particularly Cr/CrN, experienced stronger oxidation-induced phase decomposition, blistering, and local delamination. These findings identify Cr(N) solid-solution sublayers as an effective alternative to brittle ceramic nitride layers.