AN ANALYTICAL MODEL FOR PREDICTING RESIDUAL-STRESSES IN PROGRESSIVELYDEPOSITED COATINGS .1. PLANAR GEOMETRY

An analytical model has been developed to predict the residual stress distributions in progressively deposited coatings, such as those produ ced by thermal spraying. This is based on the concept of a misfit stra in, caused by either the deposition stress (e.g. due to quenching of s plats in thermal spraying) or by differential thermal contraction betw een substrate and coating during cooling. The deposition stress is int roduced as the coating is formed layer-by-layer, with a specified laye r thickness, such that the misfit strain is accommodated after each la yer addition (rather than for the coating as a whole). From a knowledg e of deposition temperatures, material properties and specimen dimensi ons, residual stress distributions can be predicted. The model is stra ightforward. It can be implemented with a simple customised computer p rogram or by using a standard spreadsheet. Comparisons are presented b etween predictions from this model and from a numerical model for thre e plasma sprayed systems. Good agreement is observed and the predictio ns also serve to highlight various features of typical sprayed systems . (C) 1997 Elsevier Science S.A.