Residual Stresses Distribution Through Thick HVOF Sprayed Inconel 718 Coatings

Paper in proceeding, 2008

Residual stress build up in thick thermal spray coatings is a property of concern. Coating adhesion to the substrate is influenced by residual stresses that are generated during the coating deposition process. In the HVOF spray process, significant peening stresses are generated during impact of semi molten particles on the substrate. The combination of these peening stresses together with quenching and thermal mismatch stresses can be of significant importance. Both numerical Finite Element Method (FEM), to calculate peening, quenching stresses, and experimental methods, i.e. Modified Layer Removal Method (MLRM) and Neutron Diffraction, have been utilised in this work. The investigation was performed on thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimisation. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.