Structure and thermal stability of arc evaporated ( Ti 0 . 33 Al 0 . 67 ) 1 − xSixN thin films

Ti0.33Al0.67)1-xSixN (0≤x≤0.29) thin solid films were deposited onto cemented carbide substrates by arc evaporation and analyzed using analytical electron microscopy, X-ray diffraction, nanoindentation, and density functional theory. As-deposited films with x≤0.02 consisted mainly of a metastable c-(Ti,Al)N solid solution for which Si serves as a veritable grain refiner. Additional Si promoted growth of a hexagonal wurtzite (Al,Ti,Si)N solid solution, which dominated at 0.02<x<0.17. For x≥0.17, the films were X-ray amorphous. Despite these widely different microstructures, all as-deposited films had nanoindentation hardness in the narrow range of 22-25 GPa. Isothermal annealing of the x=0.01 alloy film at a temperature of 900 °C, corresponding to that in turning operation, resulted in spinodal decomposition into c-AlN and TiN and precipitation of hAlN. For x=0.09 films, annealing between 600 °C and 1000 °C yielded c-TiN precipitation from the h-(Al,Ti,Si)N-phase. Furthermore, the x=0.01 and x=0.09 films