Performance evaluation of CrAlN and TiAlN coatings deposited by HiPIMS in micro drilling of a Ni-based superalloy

The current study aimed at investigating the effects of CrAlN and TiAlN coatings deposited using high power impulse magnetron sputtering (HiPIMS) on the performance in micro drilling of Incoloy 825. Influence of feed which played a major role on size effect was studied for the uncoated and coated micro drills in terms of thrust force along with its bandwidth and average flank wear. Particular emphasis was placed on the exploration of the mechanism of wear of the coated micro drills in comparison with their uncoated counterpart. Rate of rise in thrust force gradually decreased and was accompanied by a fall in bandwidth with the number of holes. HiPIMS coated micro drills were successful in mitigating thrust force, bandwidth and rate of progression of wear. However, TiAlN consistently outperformed the CrAlN coating owing to the superior hardness, coating adhesion and tribological properties. TiAlN also exhibited remarkable capabilities to resist elastic and plastic deformation under the regime of ploughing (lower feed) and the condition of higher chip load (higher feed).