Study On Thermal Stability Of(Ti,Al)N Films Prepared With PVD Technology

(Ti,Al)N and(Ti,Cr,Al)N thin films were deposited on W6Mo5Cr4V2 High Speed Steel by multi-arc ion plating technology which is in hollow cathode electron beam assisted deposition situation. The phase and surface morphology were detected and observed by XRD and SEM、CLSM. The friction coefficient、hardness、film adhesion and3 D surface topography were characterized by universal material tester. The thermal stability law of films under the experimental condition were heated at different temperature and atmosphere, and the impact on structure and properties of(Ti,Al)N with adding Cr was studied.The results show that the phase of(Ti,Al)N films was mainly composed of Ti1-xAlxN and AlTi3 N, the film surface is smoothy, the mechanical properties of films prepared by 50% Al target are below, including hardness(34.19GPa), friction coefficient(0.5573), film adhesion(37.5N). When adding Cr to the target, Cr dissolved into(Ti,Al)N forming the substitution solid solution of alternative Ti or Al from Cr,morphology and mechanical properties of films were improved, such as hardness(39.31GPa), friction coefficient(0.5173), film adhesion(41.2N).The phase composition of(Ti,Al)N films prepared by “5-5” target has almost no change, only(220) diffraction peak intensity of Ti1-xAlx N phase increased, the peak width narrowed. The structure grew slightly in impact of temperature, the surface roughness(0.3749) and hardness(28.23GPa) has no significant change, exhibiting good thermal stability in 1200℃; When heating the films in air condition higher than 800℃, the phase composition, surface roughness and hardness values have obvious changes, hardness value decreased to 12.27 Gpa and roughness is 1.8245. After heating at 900℃, the films cracked and dropped, the substrate was severely oxidized. Increasing the Al content in target to70%, the phase composition of(Ti,Al)N films has almost no change after heating at 700℃and 800℃ in air, but the diffraction peak of Ti1-x AlxN moved slightly. When heated at900 ℃ in air, the phase composition changed completely, the oxide of substrate was detected, and films cracked and failed, hardness value dropped to 13.85 Gpa.(Ti,Cr,Al) N film surface cracked at 1000 ℃ in air, the cracking temperature has increased about 100℃ compared with(Ti,Al)N. Mainly because Cr improved the oxidation resistance of Al-depleted zone in films and the formation of(Cr,Al)2O3 which can prevent inward diffusion of oxygen, in hence, oxidation resistance of films was improved.