Investigation on the Stress Behaviour of Coating-Substrate Interface under Contact Loading

This study is intended to predict the stress behavior of thick hard coating at the interface with the changes of coating stiffness and thickness to the substrate of Ti-6Al-4V and SCMV. The elastic mismatch between the coating and the substrate is presented in the value of Dundurs parameter α. The prediction is done using simple geometry of a cylinder-on-flat model in 2D analysis subjected to normal and tangential loading. Tangential stress distribution along the coating-substrate interface is then obtained from the FE modelling after a finite sliding of the cylinder. It is predicted that the maximum tangential stress value predicted at the interface which relates to coating fracture failure is increasing as stiffer coating is used on compliant substrate (i.e. increasing α values). The location of the maximum tangential stress predicted also changes from the trailing edge to the center of contact with increasing α values. Effect of changes of coating thickness on the predicted maximum tangential stress value is more significant for high positive α values. Risk of coating fracture at the interface is therefore predicted to increase with the increase of coating thickness and stiffness.