Effect of bond coat surface roughness on oxidation behaviour of air plasma sprayed thermal barrier coatings

Two layered thermal barrier coatings (TBCs) with different bond coat surface roughnesses were produced by air plasma spraying. Isothermal oxidation test was carried out to evaluate the durability and oxidation behaviour of these systems. The results show that the roughness of bond coat significantly affects the lifetime of TBCs. With the increase in bond coat roughness, the lifetime decreases exponentially. The durability is enhanced by surface grinding treatments that decrease diffusion paths on the surface of the bond coat and diminish Al depletion rate. The shape and path of cracks at failure are also affected by the bond coat surface roughness.