Interfacial Flaw Evolution of Coatings Under Severe Thermal and Pressure Transients

The effects of severe thermal and pressure transients on coated substrates with indentation-induced, blister defects were analyzed by experimental and finite element methods. Cohesive zone properties evaluated in a previous study were first used in an implicit indentation simulation. Indentation simulation results then served as the initial conditions for explicit modeling of interfacial flaw evolution due to the already determined thermal and pressure transients that included interstitial pressure in the defect. The thermal structural model was used to assess the transient thermal- and stress-states and the propensity for fracture related damage and evolution while undergoing severe convective heating and pressure loading analogous to gun tube conditions. Results illustrated the overall benefits of the in-phase applied pressure in terms of suppressing crack growth except when delayed interstitial loading was considered. Thermal capacitance was also studied and it was found that crack growth decreased significantly with higher specific heat and demonstrates the potential importance of coating thermophysical properties.