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

Abstract

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.

Impact-sliding wear properties of PVD CrN and WC/C coatings

“…The WC/C coating contains about 92.8% W and C, as well as a small amount of O (1.5%), which indicates that the WC/C coating also oxidised in the air but to a lesser degree than the CrN coating. This is attributed to the fact that the WC/C coating surface is much denser and has a much lower defect density than the CrN surface and thus the degree of oxidation is also much lower [51]. Figure 9(b,c) shows that the O content in the impact zone (point B) is slightly higher than that of the non-worn surface (1.5 and 5%, respectively), whereas O is not detected in the sliding zone (point C).…”

Geometric Influence of Hard Phase on Corrosion Performance between WC-Reinforced Coatings Prepared by High-Velocity Oxygen-Fuel Spray and Electric Contact Strengthening

“…WC-reinforced coatings are widely used in mining, oil drilling and other industries due to their excellent performance [1,2]. One of the most common WC-reinforced coatings is the WC-12Co coating.…”

Tribo-behaviour of APS and HVOF sprayed WC–Cr3C2–Ni coatings for gears

“…The thermal sprayed WC coatings with improved tribological performance could be a capable alternative solution to the chromium plating in automobile and marine industries. The government rules about environmental issues related to hard chromium plating enforced the automotive industry to work on alternatives [1][2][3]. The atmospheric plasma spray (APS) and high-velocity oxyfuel (HVOF) techniques have been commonly used thermal spray variants for numerous applications.…”

“…The cermet composite coatings demonstrated abrasive wear mechanisms, which are related to the volume fraction of binder, retained hard phases in the coatings and the grain size of carbides and binder mean free path [11]. Numerous material removal mechanisms of WC coatings are reported as follows: (i) cavities due to carbide particles pull-out [4,6,9,12], (ii) microcutting [2,9], (iii) small pits due to fractured carbide grains [13], (iv) removal of binder due to plastic deformation under higher contact pressures [6,14,15], (v) coating delamination due to severe shear stress [14], (vi) coating sublayer cracking due to fatigue [16] and (vii) ploughing due to incursion of hard particles on the coatings [2,11,15]. The optimization technique focuses on maximizing the bonding strength [17] of HVOF-sprayed WC-Cr 3 C 2 -Ni coatings.…”