Residual Stress in EB-PVD Thermal Barrier Coatings

Abstract

A NiCoCrAlY bond coating was low-pressure plasma sprayed on a stainless steel sub- strate. Zirconia with 8 wt% yttria was deposited on the bond coating using an electron beam-physical vapor deposition (EB-PVD) method. The top coating had the preferred orientation with the h111i axis direction perpendicular to the coating plane. The distribution of the in-plane residual stress in the top coating was measured using laboratory Cr-K X-rays with a progressive layer removal method. The value of the in-plane stresses was determined by the sin2 method after the separation of the 133 and 331 peaks. The distribution of the out-of-plane strain in the top coating was measured using the strain scanning method with hard synchrotron X-rays. The out-of-plane strain was obtained from the 333 peak which had strong intensity due to the preferred orientation. The measured value of the in-plane stress in the top coating was a large compression, and showed a steep decrease near the in- terface between the top and the bond coatings. The distribution of the out-of-plane stress showed a compression, and its magnitude was smaller than that of the in-plane stress.