Multi-scale modelling of the mechanical behaviour of a CoNiCrAlY bond coat alloy during small punch testing

Abstract

The present work is undertaken to determine the ability of the small punch test to determine mechanical properties of CoNiCrAlY, a two phase bond-coat material found in thermal barrier coatings. It utilises a multi-scale modelling methodology in which 2-dimensional representative volume elements of CoNiCrAlY and finite element models of the small punch test are developed. Effective Young’s moduli and Poisson’s ratios are obtained from the representative volume elements and are compared with those obtained from analytical homogenization through the Voigt, Reuss and Voigt-Reuss-Hill schemes. The volume fraction of the β-Nial phase in CoNiCrAlY is varied and the force–displacement responses of representative volume elements are contrasted with those from small punch test finite element models, through comparison of ratios of discrete fréchet distances. The results of the study estimated Young’s modulus and Poisson’s ratio to be 178.56 ± 7.65GPa and 0.249 ± 0.037 respectively, and for an increasing β-Nial phase volume fraction, the Young’s modulus and Poisson’s ratio decrease. Lastly, the results suggest that the small punch test is insensitive to variations in material elastic behaviour because its results are more influenced by the yield properties of a material.