Investigation of stress analysis on coating-substrate interfacial with pre-cracked model

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 Dundur's parameter a. 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 a values). The location of the maximum tangential stress predicted also changes from the trailing edge to the center of contact with increasing a values. Thus, evolution of stress intensity factor at crack tip, which highly depends on tangential stress distribution, was studied. A pre-micro-crack was placed at the coating-substrate interface to study the effect of stress intensity factor on stress behavior at crack tip. The stress intensity factor at crack tip does not exceed the fracture toughness due to null face friction applied to the crack seam. Effect of changes of coating thickness on the predicted maximum tangential stress value is more significant for high positive a values. Risk of coating fracture at the interface is therefore predicted to increase with the increase of coating thickness and stiffness.