Evolution of thermal stress in a coating/substrate system during the cooling process of fabrication

An analytical model is established for the thermal stress evolution in a film/substrate system during the cooling process of fabrication. Herein, heat transfer characteristics are incorporated which is critical for thermal spray coatings. The in situ temperature field solution is used to derive the instantaneous thermal stress field. Since the loss of thermal energy is account for, the new model may provide the basis for a more realistic prediction of the in situ thermal stress the fabrication process. The magnitude of thermal stress derived from the present model is lower than that of the classic one. The thermal stress is generated quickly and significantly during the initial seconds of the cooling process, and stabilizes later. The effects of several spray factors, such as the pre-heat temperature and the thicknesses of coating and substrate, are discussed and compared with a parallel experiment.