Delamination Energy Evaluation of 8mass% Y2O3-ZrO2 Coating Sprayed on Co-Based Superalloy
Masahiko KATO, Keijiro NAKASA, Lin GAO, Teruhito BANSHO, Hidetaka NISHIDA and Hiroshi YAMAGUCHI
Abstract:In order to evaluate the delamination strength of Y2O3-ZrO2 ceramics coating deposited on Co-based superalloy with CoNiCrAlY bond coat, the tensile test and the edge-indent test were carried out. When the tensile load is applied to the specimen, the ceramic coating is divided by parallel cracks, and the cracks propagate not only along the interface but also into the bond coat layer until the delamination of top coat. With an additional load, the bond coat layer also delaminates. The equation to obtain the critical strain energy release rate Gci/I+1 or the interfacial fracture toughness between I and I+1-th layers for the coating of (n-1) layers on a substrate is introduced fracture-mechanically, and the experimentally measured GC1/23 between the ceramic coating layer and the bond coat layer is lower than that between the CoNiCrAlY bond coat layer and the substrate. The delamination energy of ceramic coatings measured by the edge-indent tests almost correspond to GC1/23. Both the tensile and the edge-indent methods are applicable to evaluate the delamination strength of double layer coating specimen as well as the single layer coating specimen. Key Words:Delamination strength, Co-based superalloy, Y2O3-ZrO2 ceramics, Tensile test, Edge-indent test