Abstract
High Velocity Oxy-Fuel (HVOF) spraying is one of the preferred surface engineering technologies that can offer advantages such as user-friendliness and cost-efficiency in mass production of coatings for various applications. While the main applications of the HVOF process are related to wear, corrosion resistance can be one of the important desired features of the surface engineering process. However, the porosity of HVOF sprayed coatings is usually a problem when coatings are used in corrosion applications. Low carbon steel substrates were High-Velocity Oxygen Fuel (HVOF) sprayed with Inconel 625 and then coated with a thin film of electroless nickel (electroless nickel plating). Reference sample without electroless nickel was sprayed at the same time. Characterization of the coatings was made by X-Ray diffraction analyses, microstructural surveys, cross-section and corrosion tests. Results showed that sequential application of HVOF spraying and electroless coating processes provided the multi-layered coating consisting of an inner inconel 625 based layer and an outer Ni-P layer. Electroless Ni-P also caused the remarkable increasing in the corrossion resistance as compared to the as-HVOF sprayed state.
Highlights
The use of thermal sprayed corrosion-resistant coatings to protect an underlying steel substrate has received much interest over the past few years (Johnson et al, 2011)
Deposited Inconel 625 coating designed for use in harsh service environments can be damaged because some residual oxides and porosity remain at splat boundaries (Rakhes et al, 2011; Poza et al, 2014)
It was found that the laser coating demonstrated poor corrosion performance because cracking due to rapid melt pool solidification acted as sites for crevice and pitting corrosion (Abioye et al, 2015)
Summary
The use of thermal sprayed corrosion-resistant coatings to protect an underlying steel substrate has received much interest over the past few years (Johnson et al, 2011). The advantage of this method is the substantial weight and cost reduction compared to using bulk alloys (Hjornhede and Nylund, 2004). Deposited Inconel 625 coating designed for use in harsh service environments can be damaged because some residual oxides and porosity remain at splat boundaries (Rakhes et al, 2011; Poza et al, 2014). We carried electroless deposition process to improve the corrosion performance onto the HVOF sprayed Inconel 625 coating to reduce corrosion attack at the coating surface to any open porosity or splat boundaries. According to the available literature, there is no such report on the HVOF sprayed Inconel 625 coating deposited with
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