Thermal shock behaviors of Ti1−xZrxN coatings by accelerated test based on pulsed laser ablation

Abstract

The degradation behaviors of Ti1−xZrxN coatings on SUS304 were investigated through an accelerated test method using a pulsed laser to induce thermal shock. The accelerated test was designed based on the Arrhenius model, and the changes in surface roughness were measured to determine the failure of the coating specimens. The predicted lifetimes obtained by a statistical analysis of the failure time data were increased by a factor of ~1.5 according to the increase in the Zr ratio from 10 to 50wt%. The increase of the lattice parameters and hardness for the as-deposited specimens indicated lattice volume expansion and distortion according to the Zr addition, respectively. Depth profiles for the coating (Ti, Zr) and the substrate (Fe, Cr) atoms revealed that the atomic diffusion distance by laser ablation decreased with lattice distortion. Delamination of the coating layer was only observed in the specimen with 10wt% of Zr after repeated thermal shock. The coating thickness decreased with surface cracks and was suppressed in the specimens with 30 and 50wt% of Zr by the increase of ZrN formation.