Residual Stress Calculations in Coating Configurations Using Finite Element Analysis

Abstract

The use of oxidation-resistant, high toughness, adherent coating configurations would significantly reduce surface damage and strength loss in advanced gas turbine engine components which are in sliding contact. However, due to the mismatch in the thermal and elastic properties of coatings and substrates, residual thermal stresses induced during the coating deposition process would lower the thermal shock resistance of the component. Linear thermoelastic stress analysis by the finite element method was used with the aim to aid selection of suitable coating configurations which would yield low residual stresses in the coatings. Because typical coating thicknesses are orders of magnitude smaller than the dimensions of the substrates, it is very taxing on conventional finite element procedures to obtain accurate numerical solutions. Such a difficulty was overcome by using a hybrid finite element in the procedure in the thermoelastic stress analysis. The development of this procedure which is based on a mixed formulation and an assumed stress field is outlined, and residual stress distribution on candidate coating configurations is presented.