A parametric study on residual stresses induced by cold spraying Ti-6Al-4V on Ti-6Al-4V substrates

Cold spray (CS) is a solid-state additive material deposition technique, which has gained attention in the aerospace industry as a potentially viable technology for structural repair of high value parts made of high-strength alloys such as Ti-6Al-4V (Ti-64). The distribution and magnitude of residual stresses that build up in the substrate and deposited materials during cold spraying can influence the mechanical performance, substrate-deposit adhesion, cohesion between deposited layers, and overall integrity of a coating or repair. However, the nature, magnitude and distribution of residual stresses in Ti-6Al-4V/Ti-6Al-4V CS repairs are currently unknown. This study aims to evaluate the effects of geometrical variables (number of CS layers, individual CS layer height, and substrate height), track pattern and post-deposition heat treatment on the magnitude and distribution of residual stresses in cold spray deposit-substrate assemblies. Residual stress profiles were measured experimentally by contour method and neutron diffraction at ENGIN-X, ISIS Neutron Source, UK. An analytical model was developed to predict the through-thickness residual stress distributions which were validated by the experimental measurements.