A comparative research on TiAlN coatings reactively sputtered from powder and from smelting TiAl targets at various nitrogen flow rates

The deposition rate achieved with the powder targets was ∼30% higher than that obtained from the smelting targets. TiAlN coatings deposited by two types of targets have totally different surface morphology. The surface roughness of the coating with powder target was 20% lower than with smelting target. The number of metallic macro-particles in the coating prepared by powder target was fewer than that by smelting target as a function of the nitrogen flow rates. The phase of coatings is related to the nitrogen flow rate. When the nitrogen flow rate is 20 sccm, both coatings have a phase c-TiN. When the nitrogen flow rate is >20 sccm, both coatings exhibits a stable phase Ti2AlN. The formation of Ti2AlN was attributed to the nitrogen concentration in the coatings and the elevated deposition temperature. The coatings grown from powder targets showed superiority in adhesion strength but less well-behaved in hardness, which is in contrast to those synthesized from the smelting targets.