The role of structural properties on damage behaviour of titanium and aluminium nitride coatings: An EXAFS and TEM study

Indentation tests are performed on a set of Ti1 − xAlxN films prepared in various compositions by reactive magnetron sputtering. Ti K-edge X-ray absorption fine structure spectra recorded by focusing the beam onto the centre of typical indentation craters and onto undamaged area are compared. For cubic TiN and Ti0.50Al0.50N, the octahedral Ti environment remains unchanged under indentation tip. EXAFS analysis reveals that about 60% of Ti atoms are located in hexagonal lattice of Ti0.32Al0.68N film against about 40% in cubic-like octahedral environment. The short-range order around Ti atoms substituted for Al in hexagonal lattice undergoes strong distortions when the film is submitted to indentation test. Furthermore, cross-sectional images of typical indentation prints reveal a more and more brittle behaviour as increasing Al content in Ti1 − xAlxN coatings.