Texture determination in highly stressed PVD thin films

Growth texture and residual stress in TiN thin films on 304 stainless steel were studied by XRD in parallel beam configuration. The high residual stress deeply influenced texture determination by conventional methods based on pole figures. Area maps (collections of 8-28 patterns at regular steps of v-tilting) were used to properly assess the mixed [21 l]/[l 1 l] growth mechanism in the nitride thin film, and for a detailed study of the residual stress analysis within the coating and outer layers of the substrate. The residual stress trend in the TiN thin film was studied considering data from (111) and (200) reflections, in order to avoid the effects of the fibre texture on the mechanical anisotropy. In particular, a residual stress gradient of the in-plane stress component was obtained for the thin film, whereas average in-plane stresses were calculated for the Martensitic layer at the thin film - substrate interface and for the outer layers of the substrate Austenitic phase underneath. It was also proposed that the use of Area Maps can be extended to study thickness and layer sequences, as well as microstrain and domain size effects connected with profile width and shape, in order to provide a detailed picture of thin film and interface features.