Effect of fluid scour on stress distribution of film-substrate system

Under strong fluid scour in special service environment, the film-substrate system is prone to weaken its mechanical properties due to the additional shear stress by fluid, resulting in film debonding. The present study establishes a mechanical model incorporating the fluid shear stress for a film-substrate system with partial debonding. The debonding length, scour strength and thermal mismatch are considered in the model, respectively. Fluid induces compressive stress on inflow side and tensile stress on outflow side. Potential debonding behavior of film by the additional shear stress is qualitatively analyzed. Results show that the compressive stress by fluid releases part of the tensile stress of thermal mismatch, may mitigate surface cracking of film. The surface scour effect is amplified by the partial debonding, and is further enhanced with the increase of debonding length. The unevenness of stress distribution at the interface is intensified by the debonding and fluid scouring. The fluid scour poses a potential threat to the film-substrate system.