Multiscale Fracture of Ti-Al-N Coatings under Uniaxial Tension

The fracture behavior of Ti0.45Al0.55N coatings under uniaxial tension was investigated at different scale levels. The coatings were deposited on 12Cr18Ni9Ti steel substrates by direct current reactive magnetron sputtering. According to molecular dynamics simulation, the nonuniform distribution of aluminum in the coatings affects the initiation and growth of cracks in them. It was found experimentally that the macroscopic fracture of Ti0.45Al0.55N coatings on a metal substrate under uniaxial tension occurs in four stages, whose duration is determined by the competition between different stress relaxation mechanisms. The effect of the coating thickness on the development of competing deformation and fracture mechanisms in the coatings is demonstrated.