Journal of the American Ceramic Society, Vol.101, No.2, 845-855, 2018
Structure, mechanical, and thermal properties of Ti1-xAlxN/CrAlN (x=0.48, 0.58, and 0.66) multilayered coatings
Nano-multilayered TiAlN/CrAlN coatings combining advantages of Ti-Al-N and Cr-Al-N are considered to be promising candidates for advanced machining processes. Here, the structure and thermal properties of Ti1-xAlxN/CrAlN (x=0.48, 0.58, and 0.66) multilayered coatings as well as referential Ti1-xAlxN and Cr0.32Al0.68N monolithic coatings were investigated. Ti1-xAlxN coatings show a structural transformation from cubic structure for x=0.48 to mixed cubic and wurtzite structure for x=0.58 and 0.66, and Cr0.32Al0.68N coating exhibits a single cubic structure. Through a multilayer arrangement with Cr0.32Al0.68N layers, the Ti0.52Al0.48N and Ti0.42Al0.58N layers can be stabilized in their metastable cubic structure, but the Ti0.34Al0.66N layer still tends to crystallize in the mixed cubic and wurtzite structure. The hardness of Ti0.52Al0.48N/CrAlN and Ti0.42Al0.58N/CrAlN coatings is higher than that of corresponding monolithic coatings regardless of as-deposited and annealed states. Especially, after annealing at 800 degrees C, the Ti0.52Al0.48N/CrAlN and Ti0.42Al0.58N/CrAlN coatings reach their peak hardness of similar to 34.2 and 32.8 GPa due to the spinodal decomposition of Ti1-xAlxN layers. However, the oxidation resistance of Ti1-xAlxN/CrAlN coatings is mainly up to the Al content of Ti1-xAlxN layers, where only the Ti0.34Al0.66N/CrAlN coating can survive the 10h exposure to air at 1000 degrees C.