Influence of WC-20Co-1Ni coating by HVOF on lifespan of the downhole drilling motors

Downhole drilling motor is one of the equipment used for drilling and they perform the task of directional drilling. The rotor of these motors is made of 17-4 PH steel, which is generally coated with hard chromium. In this study, the feasibility of replacing hard chromium with WC-20Co-1Ni using a high velocity oxygen fuel system was examined. The result of the metallurgical and mechanical examination showed that changing of the coating to WC-20Co-1Ni improved the wear performance and increased the lifespan of the rotor. In addition, the chemical resistance to corrosion due to the influence of the corrosive gases in the hole on the rotor improved significantly. Finally, substitution of the hard chromium coating with the WC-20Co-1Ni caused an increase in the lifespan and performance of the downhole motor in extreme environmental conditions of the drilling formations, which led to economic savings in amendment and maintenance costs.