H. Y. Al Fadhli, Saudi Oil Comapny, Dhahran, Saudi Arabia; T. Ghamdi, Saudi Aramco, Dhahran, Saudi Arabia; B. S. Yilbas, Y. A. Al Shehri, Saudi Oil Company, Dhahran, Saudi Arabia
This paper presents the effect of the residual stresses resulted from thermal spray coating applied over welded surfaces. The temperature variation and residual stresses response of Inconel-625 powder thermally sprayed using High Velocity Oxygen Fuel (HVOF) coating was theoretically and experimentally evaluated when it was applied over three different metallic surfaces: (a) plain stainless steel (SS), (b) spot welded stainless steel (SW-SS), and (c) composite surface of stainless steel and carbon steel welded together (C-SS-CS). ANSYS finite element analysis was used to predict the temperature variation during the cooling process as well as residual stresses effect resulted from having different substrate compositions. These results were also supported using analytical techniques for determining residual stress in deposits. To compare the finite element analysis results with experimental test, the three different substrate was sprayed using Inconel-625 powder and exposed to various corrosive environments and subjected to fatigue, bending and tensile mechanical tests. The surface morphology and the elemental composition of the coating before and after the mechanical tests were examined using SEM and EDS techniques. Finite element analysis results showed that there is a slight variation in the temperature and residual stresses due to having different physical properties of the metallic substrates, but this variation is minimal and below the yielding tensile strength of the tested material. These results were supported experimentally indicating that varying the substrate composition or having a weld spots in the substrate is not much affecting the coating substrate bonding even when it is subjected to various mechanical tests under highly corrosive environments. Microscopic observations of the coating substrate interface showed that the HVOF coating is mainly dependant on the mechanical interlocking and not of coating substrate metal diffusion.
Summary: This paper presents the effect of the residual stresses resulted from thermal spray coating applied over welded surfaces.
