The application of thick HVOF coatings on metallic parts has been widely accepted as a solution to improve their wear properties. The adherence of these coatings to the substrate is strongly influenced by the residual stresses generated during the coating deposition process. In an HVOF spraying process, due to the relatively low processing temperature, significant peening stresses are generated during impact of semi-molten particles on the substrate. At present, FE models of residual stress generation for the HVOF process are not available due to the increased complexities in modelling the stresses generated due to the particle impact. In this work, deposition of an HVOF sprayed copper coating on a copper substrate is considered as an example system. An explicit finite element analysis is carried out to study the effect of particle impingement. The results from the analysis are subsequently used in a thermo- mechanical FE model to allow the development of the residual stresses in these coatings to be modelled.

The acoustic emission (AE) technique, when used with the four-point bend test, is potentially an effective method for characterization of the ductility and fracture behaviour of certain thermally sprayed coatings. Monitoring of AE during such tests on brittle coatings reveals that the rate of the occurrence of events with increasing load changes gradually over the duration of the test. In this work, finite element modelling (FEM) of a brittle coating on an elastic substrate in four-point bending is used to analyze the fracture behaviour of the coating and predict its AE behaviour. The results from the FE analysis show good agreement with experimental data from four-point bending of thermally sprayed WC-Co coatings.