Analysis of Interface Fracture of Cold Sprayed Coatings Due to Thermal Cycling

Driving mechanisms for the interface fracture of cold sprayed chromium/steel coating subjected to a cyclic thermal loading are studied by using thermomechanical analysis. First, the equilibrium stress states of the chromium coated steel substrates are determined for different coating thickness vales. The coated systems are then subjected to periodic heating and cooling cycles. Crack initiation and growth in the systems are simulated with and without embedded micro-cracks. The corresponding crack driving forces are characterized using the interface stresses, energy release rate and stress intensity factors as a function of the thermal cycles. The effects of coating thickness, location of embedded micro-cracks and initial residual stresses on these driving forces are investigated systematically to demonstrate the risk of coating fracture and delamination. The corresponding possible causes for the major driving force under these effects are also explored to better understand the potential transition of peeling- and shearing- dominated fracture mechanism during the thermal cycles.