2002 Volume 51 Issue 1 Pages 95-100
Thermal barrier coating (TBC) was applied on the Co based superalloy specimens, where CoNiCrAlY bond coat was deposited by high velocity oxygen fuel (HVOF) spraying and 8mass% yttria stabilized zirconia (YSZ) top coat by atmospheric plasma spraying. The isothermal oxidation behavior of TBC at high temperature was characterized by scanning electron microscopy, EPMA mapping analysis, energy dispersive spectroscopy and X-ray diffraction. The Alumina and complex oxide layers were formed along the interface between the top coat and the bond coat, and the thickness of the oxide layers increased with increasing heating temperature and holding time. When the delamination of the top coat occurred during the holding of the specimen at 1473K for 1732ks and on cooling after holding at 1273K for 3960ks, half-sphere-shaped cracks grew along the interface between unmelted bond coat particles and Al2O3 layer, and propagated in the complex oxide or the top coat. In tensile test and edge-indent test, the delamination of top coat started near the top of particles and extended in the top coat under shear stress.
