Influence of porosity characteristics in MgO.ZrO2-GG coating subjected to thermal loading

In this investigation, coupled (thermal and structure) finite-element analysis has been employed to analyse the influences of porosity volume, size and distribution in MgO.ZrO2-GG coating subjected to thermal loading. Coatings with and without NiAl interlayer material were modeled. All models had a 1/10 coating-to-substrate thickness ratio and a porosity ratio of 3% and 7%. The porosity location and distribution were also considered and modeled. Thermal stresses at the vulnerable areas (film/substrate) were obtained and compared. The results showed that the volume, size, location and distribution of the porosity have a significant influence on the level of the developed thermal stresses. In the case of MgO.ZrO2-GG coatings the optimum low-level stresses are developed with 7% small-size uniformly-distributed porosity allocated far away from the coating surface. (C) 1997 Elsevier Science Ltd. All rights reserved.