Multilayered coatings with alternate pure Ti and TiN/CrN superlattice

Multilayered coatings containing alternating layers of pure Ti and TiN/CrN superlattice were deposited with controlled layer thickness and superlattice bilayer period using pulsed DC magnetron sputtering technique. The preferred orientation of the TiN/CrN superlattice constituent was either (1 1 1), (2 0 0) or random depending on the sub-structure between the Ti and superlattice layers. Nano-indentation testing showed that mechanical properties of the coatings varied with the bilayer period, crystallographic orientation and volume fraction of superlattice layers in the coatings. For the same bilayer period and superlattice volume fraction, coatings with (2 0 0)-oriented superlattice layers were harder than those with randomly and (1 1 1)-oriented superlattices. Scratch testing revealed severe interfacial failure between coating/substrate and superlattice/Ti layers. Due to the brittle nature of the superlattice layers and weak interfacial strength, these multilayered coatings exhibited poor performance in erosion testing involving high-speed particle impingements, which caused extensive cracking and localized interfacial detachments between the coating and substrate and between the superlattice and pure Ti layers.