An experimental and numerical study of a CoNiCrAlY coating using miniature specimen testing techniques

Abstract

Small punch tensile (SPT) tests have been carried out for a CoNiCrAlY coating at room temperature (RT), 500 °C and 700 °C. Highly re-producible results have been obtained for SPT at 700 °C while the formation of early cracking at lower temperatures tends to compromise the repeatability of the tests. An alternative novel miniature specimen testing method has been developed and used for the miniature tensile tests of the CoNiCrAlY coating in the same temperature range. Good agreements have been achieved between the SPT and miniature tensile testing results regarding the ductile to brittle transition temperature (DBTT). Excellent repeatability has been achieved over the full range of the temperature for the miniature tensile tests. An inverse approach has been developed and used to extract the mechanical properties of the material from the miniature tensile tests, using a temperature-dependent Johnson-Cook model. Finite element (FE) modelling of the SPT tests, including damage evolution, has been carried out using the extracted material properties to give comparable predictions of the SPT testing results, such as the load-displacement curves and the approximate locations of the fracture failures.