High-temperature thermal stability and oxidation resistance of Cr and Ta co-alloyed Ti - Al - N coatings deposited by cathodic arc evaporation

Cr and Ta co-alloyed Ti - Al - N coatings were synthesised by cathodic arc deposition. The high-temperature stability and oxidation behaviour of the coatings were investigated by annealing in an inert atmosphere and oxidation environment, respectively. The results indicated that FCC-structured (Ti, Al, Cr, Ta)N coatings exhibit spinodal decomposition and age-hardening upon annealing. Ta retarded the formation of wurtzite A1N and helped to maintain high coating hardness at 900-1000 degrees C. Cr promoted the formation of protective (Al, Cr)(2)O-3 scale and (Ti, Ta)O-2 rutile oxide was found beneath, which reduced mass transport of oxygen during oxidation. Co-alloying with Cr and Ta leads to optimal oxidation resistance of (Ti, Al, Cr, Ta)N coatings.