Thermal cycling behavior of plasmsa-sprayed thermal barrier coatings with various MCrAlX bond coats

The influence of bond coat composition on the spallation resistance of plasma-sprayed thermal barrier coatings (TBCs) on single-crystal Rene N5 substrates was assessed by furnace thermal cycle testing of TBCs with various vacuum plasma spray (VPS) or air plasma-sprag (APS) MCrAlX (M = Ni and/or Co; and X = Y, Hf, and/or Si) bond coats. The TBC specimens with VPS bond coats were fabricated using identical parameters, with the exception of bond coat composition. The TBC lifetimes mere compared with respect to MCrAlX composition (before and after oxidation testing) and MCrAlX properties (surface roughness, thermal expansion, hardness, and Young's modulus). The average TBC spallation lifetimes varied significantly (from 174 to 344 1 h cycles at 1150 degrees C) as a function of bond coat composition. Results suggested a relationship between TBC durability and bond coat thermal expansion behavior below 900 degrees C. Although there mere only slight differences in their relative rates of cyclic oxidation weight gain, VPS MCrAlX bond coats with better oxide scale adhesion provided superior TBC lifetimes.