Effect of Al content on the microstructure and mechanical properties of Mo–Al–Si–N films synthesized by DC magnetron sputtering

Mo–Al–Si–N films were deposited by reactive magnetron sputtering on substrates of Si wafer, alumina, and stainless steel from composite targets consisting of Mo, Al and Si. To investigate the effect of Al content on the properties of the Mo–Al–Si–N films at a constant Si content of 9 at.%, the chemical composition, microstructure, surface morphology and mechanical properties of these films were characterized by means of energy dispersive spectrometer, X-ray diffraction, field emission scanning electron microscopy, nanoindentation, and thermogravimetric analysis. It was found that the preferred orientation of the Mo–Al–Si–N films is (111) at lower Al content and gradually changes into (200) with increasing Al content. The hardness and elastic modulus of the Mo–Al–Si–N films initially increases and then decreases with increasing Al content, after passing the maximum values of 29 GPa and 350 GPa at 10 at.% Al, respectively. The oxidation temperature of the Mo–Al–Si–N films increases to 610 °C when the Al content reaches 13 at.%. These results demonstrate that the addition of 10 at.% Al can improve the properties of the Mo–Si–N films containing 9 at.% Si.