Thermally sprayed Inconel 625 coating on 304 stainless steel: A neutron diffraction stress analysis

The aim of this project is to enhance fundamental understanding and gaining knowledge about the mechanism and factors controlling the residual stress formation in the Inconel 625 coating on 304 Stainless steel substrates, with potential application to coupled bi-metal(?) materials. It is noted that designing high-performance coatings with long-term active corrosion protection for such components will add value to many strategic industries, including the automotive and aerospace sectors. In this paper, the investigation was conducted to characterise stress and mechanical properties of Inconel 625 with different thicknesses, 300µm and 400µm, deposited on 304 stainless steel (SS) substrate using high-velocity oxy-fuel (HVOF) spraying technique. The coating characterization was carried out to determine the optimal coating thickness to be applied on 304 SS substrates that achieves the best coating performance. The residual stresses were systematically characterized to understand the influence of coating thickness within the coating vicinity using the neutron diffraction technique. The results indicate that the residual stressed were compressive in nature but of slightly different magnitude despite using the same powder as feedstock. This was attributed to the influence of thermal and cooling effect that plays a major role in the coating build-up or some possible random factors.