Comparison of residual stress generation in high kinetic HVOF and HVAF processes

Comparison of residual stress generation in high kinetic HVOF and HVAF processes Tommi Varis, Tomi Suhonen, Mika Jokipii, Jarkko Metsäjoki Thermal spray processes has been developing towards lower particle temperature and higher velocity. Newest generation HVOF and HVAF produce very dense coating structures, due to the higher kinetic energy. High kinetic energy also generates higher peening stresses and final residual stresses (thermal mismatch, quenching and peening) have a significant role on the coating mechanical response and fatigue behaviour of the coating. Understanding these effects is detrimental for damage tolerant coating design. In this study, comparison of residual stresses in various thermal spray systems HVOF (CJS and DJ Hybrid) and HVAF (AcuKote from Kermetico, USA) was measured by in situ techniques, which offers tool to evaluate the origins of residual stresses on each coating substrate system. The effect of different particle temperature-velocity characteristics on the deposition efficiency was also determined. The research has been done for various particle densities to study the effect of particle morphology on the residual stress.