Influence of Doping with Si and Y on Structure and Properties of (ti, Al)N Coating

Composite metastable Ti0.3Al0.7N and Ti0.39Al0.55Si0.05Y0.01N hard coatings were deposited on a wrought martensite steel 1Cr11Ni2W2MoV for aero-engine compressor blades by the magnetron sputtering system with the bias voltage of 0 and -100 V respectively Detailed microstructure, chemical composition, crystal structure, hardness and adhesion were examined by means of FESEM, EDS, XRD, Micro hardness tester and scratch tester. The influence of doping with Si and Y and bias on structure, oxidation-resistance and mechanical properties of (Ti, Al)N coatings were investigated. Pulsed bias and the doping with Si and Y gave rise to the change of phase structure and improvement of density. Doping with small amounts of Si and Y into (Ti, Al)N significantly improved the oxidation resistance at 950 degrees C. The oxidation-resistance of (Ti, Al, Si, Y)N is based on the formation of dense protective Al2O3 layer. The application of negative pulse led to decreased hardness for (Ti, Al)N while remarkable decrease of hardness for (Ti, Al, Si, Y)N. For (Ti, Al, Si, Y)N prepared under -100 V bias, annealing 10 h at 950 degrees C slightly decreased it's hardness because of the formation of B4 structure. And for which deposited at 0 V bias, heat-treatment of 950 degrees C for 10 h improved the hardness from 26 GPa to 35 GPa. The hardness change of the coating may be ascribed the transition of B1. phase structure. Scratch tests show that the continuous span is not occurred for all the coatings under the critical load of 50 N.