Orientation dependence of the fracture mechanisms in (V,AI)N coatings determined by micropillar compression

Transition metal aluminium nitrides produced by physical vapour deposition are widely used as hard, protective coatings in the manufacturing industries. To optimise coatings wear resistance while maintaining fracture toughness, an understanding of the mechanisms linking the microstructure and the orientation-dependent fracture behaviour is required. (V,AI)N coatings were synthesised by direct current and high power pulsed magnetron sputtering. Uniaxial compression testing was performed using micropillars oriented between 0 degrees and 90 degrees with respect to the growth direction to assess the effect of microstructure on the fracture behaviour. We show here that different fracture mechanisms are active depending on the alignment of grains and loading direction. The fracture behaviour could be divided into three classes associated with column buckling, decohesion or shearing and no significant difference between the specimens induced by the deposition process could be observed.