Effect of annealing on the hardness and microstructure of Cr-Zr-O coatings

The hardness and microstructure of as-deposited and annealed Cr-Zr-O coatings have been comparatively investigated to clarify the effects of annealing treatment. The as-deposited coating comprises of nano-sized columnar grains of (Cr, Zr)2O3 that is formed due to the solution of Zr atoms in Cr2O3. Such a kind of structure is benefit for the hardness. The interface between the as-deposited coating and substrate is well-bonded and a sandwiched structure forms during the deposition process. After annealing at 800 °C, a high density of nano-sized voids were formed in the coating. The sandwiched structure at the interface is damaged and the bonding of interface becomes weak. As a result, the modulus and hardness of the Cr-Zr-O coating decrease significantly after annealing.