Impact and Indentation Resistance of Superhard AlCrN Thin Films

Abstract

Binary transition metal nitride films have excellent tribological properties but these binary systems are still inadequate for high temperature applications due to their low oxidation temperature. Above 700°C, formation of porous oxides at the film surface deteriorates their mechanical properties rapidly by the. Especially impact and indentation resistance of these films deteriorate very quickly. In order to overcome these problems, Al based Al1-xCrxN films with X=0.29 and X=0.69 were synthesized by closed field unbalanced magnetron sputtering with vertical magnetron sources and their chemical composition, crystalline structure, morphology and mechanical properties including impact and indentation resistance were investigated. Synthesized Al1-xCrxN films formed solid solution showing FCC B1 type structure with strong (111) preferential orientation and films with X=0.29 showed a superhard hardness value of approximately 41GPa while films with X=0.69 did approximately 31GPa. While there was insignificant difference between Al1-xCrxN films with X=0.29 and X=0.69 in terms of Rockwell C indentation resistance, much improved impact resistance could be observed from the Al1-xCrxN films with X=0.29.