A finite element analysis technique for predicting as-sprayed residual stresses generated by the plasma spray coating process

It is essential to analyze the residual stresses during the deposition of plasma sprayed coatings since they adversely affect the coatings' performance during their service. In this article, finite element coupled heat transfer and elastic-plastic thermal stress analysis using a general purpose commercial FEM software ANSYS (ANSYS Inc., Southpointe, PA, USA) are presented to simulate the in situ residual stress generation during plasma spraying of duplex thermal barrier coatings (TBCs). The complicated physical spray process was idealized and a multiple layer-by-layer coating structure was assumed. In the simulation, the geometry was updated layer by layer and results from the previous layer analysis, including temperature and displacement, were used as loads for the current layer analysis. The predicted specimen temperature and curvature agreed well with those experimentally measured by thermocouples and a specially designed laser-displacement-measurement system, respectively. A simple method by post-deposition treatment was also proposed to effectively reduce the residual stress level in the coated specimen, with the possibility of eliminating the residual stress.