The effect of the addition of Al and Si on the physical and mechanical properties of titanium nitride

In this work it will be shown that the addition of Al and Si improve not only the oxidation resistance of TiN, but also its adhesion behaviour. For this, Ti1-xSixN and Ti1-yAlyN coatings with 0 less than or equal to x less than or equal to 0.3, 0.38 less than or equal to y less than or equal to 0.81 and of thickness ranging from 1.2 to 5.6 mu m, were deposited onto polished high-speed steel substrates by de and rf reactive magnetron sputtering. Samples were oxidised in air at temperatures of between 500 and 900 degrees C. The atomic composition was measured by means of Rutherford Backscattering Spectrometry (RBS) and the texture by X-ray diffraction (XRD). Adhesion behaviour was characterised by scratch test experiments. The results show a great improvement in oxidation resistance for both Ti1-xSixN and Ti1-yAlyN systems when compared with that of TiN. For the Ti1-yAlyN system, higher oxidation resistance was observed for y = 0.65, which is the value where the best results for critical loads were observed. For the Ti1-xSixN system, the best oxidation performance was observed for x = 0.3, but the highest critical loads were obtained for x = 0.15. (C) 1999 Elsevier Science S.A. All rights reserved.