Oxidation behavior and mechanical properties of laminated Hf–Ta coatings

Abstract

This study explores the internal oxidation of laminated Hf–Ta coatings with a cyclically gradient chemical concentration distribution along the growth direction. The oxidation behavior was examined by annealing the coatings at 400–600°C in a 15ppm O2–N2 atmosphere for 30min. The variations in crystalline structure, nanohardness, chemical states, and chemical composition profiles in depth after various annealing conditions were investigated. The results indicate that all the Hf–Ta coatings maintain a laminated structure after annealing at 400–600°C. Internal oxidation conducts during 500 and 600°C annealing, but part of the outmost layers exhibits complex oxides after annealing at 600°C. The nanohardness of annealed Hf–Ta coatings related to the formation of HfO2, Hf6Ta2O17, and amorphous Ta-oxide were studied.