Tribological and mechanical properties of structure-modulated Cr_XN coatings fabricated by HiPIMS

CrN coatings with monolithic CrN, composition gradient Cr_XN, multilayer Cr/CrN, and alternating compositional gradient Cr_XN structures are deposited on silicon wafers and 304 stainless steel substrates using high power impulse magnetron sputtering technique. This study systematically investigates the microstructures, mechanical properties, tribological characteristics, and electrochemical corrosion resistance of these coatings, exploring their interrelations. All coatings are prepared under identical average power conditions, with the monolayer exhibiting a continuous columnar crystal structure. The gradient structure progressively developed three microstructural characteristics along its growth direction: Cr phase, Cr₂N phase, and CrN phase. The multilayer structure manifested as a periodic columnar crystal structure with distinct phase interfaces, while the alternating component gradient structure presented a large number of irregular polygonal configurations, and these grains are closely packed, suggesting a “staggered arrangement” structural morphology. Due to the continuous growth of columnar crystals in monolayer coatings, numerous interconnecting inter-columnar gaps between the surface and substrate led to the highest corrosion current density. For the gradient structure, the high-volume fraction of ceramic phases and the presence of the hard Cr₂N phase contributed to achieving the highest hardness of 23.6 GPa, though with inferior crack propagation resistance. The multilayer structure, characterized by the highest proportion of metal phases and a layered structure, demonstrated superior crack resistance and the highest corrosion potential. The alternating compositional gradient structure, designed with small-scale compositional gradients and a cyclic layered structure, attained optimal wear and electrochemical corrosion resistance while preserving high hardness. This design greatly improves the damage tolerance of the coating and provides a new idea for the structural design of hard Cr_XN coating which is resistant to wear and corrosion.