Phase Composition, Hardness, and Thermal Shock Properties of AlCrTiN Hard Films with High Aluminum Content

Abstract

TiCrAlN hard films based on TiN or CrN show superior properties in terms of hardness, wear resistance, and thermal stability due to the addition of alloying elements. AlCrTiN films based on AlN may have higher thermal shock properties, but the knowledge of AlCrTiN films with high Al content has been insufficient until now. In this study, two sets of AlCrTiN hard films with different Al contents of 48 at.% and 58 at.% among metal components were prepared via multi-arc ion plating so as to investigate the effect of Al content on the phase composition, hardness, and thermal shock resistance of the films. The same microstructures, morphologies, and thicknesses of the fabricated film samples were achieved by changing the combination of cathode alloy targets and adjusting the arc source current during deposition. The surface chemical composition, cross-sectional elemental distribution, microstructure, morphology, phase composition, surface hardness, film/substrate adhesion strength, and thermal shock performance of the AlCrTiN films were examined. The obtained results reveal that the two sets of AlTiCrN hard films are face-centered cubic solid solutions with a columnar fine grain structure and a preferred growth orientation of (200) crystal plane. The hardness of the AlCrTiN films can be improved up to HV2850 by properly reducing the Al content from 58 at.% to 48 at.%. Meanwhile, the film/substrate adhesion performance is strong enough in terms of critical loads greater than 200 N. Furthermore, the AlCrTiN films maintain high thermal shock resistance at 600 °C when the Al content decreases from 58 at.% to 48 at.%. The optimal composition of the AlCrTiN hard films is 25:13:15:47 (at.%), based on the consideration of hardness, adhesion, and thermal shock cycling resistance. This optimal AlCrTiN hard film can be suggested as an option for protective coatings of hot process die tools.