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 plas ma-sprayed thermal barrier coatings (TBCs) on single-crystal Rene N5 substr ates was assessed by furnace thermal cycle testing of TBCs with various vac uum 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 coa t composition. The TBC lifetimes mere compared with respect to MCrAlX compo sition (before and after oxidation testing) and MCrAlX properties (surface roughness, thermal expansion, hardness, and Young's modulus). The average T BC 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 behav ior below 900 degrees C. Although there mere only slight differences in the ir relative rates of cyclic oxidation weight gain, VPS MCrAlX bond coats wi th better oxide scale adhesion provided superior TBC lifetimes.