Effect of a nanoparticulate anti-friction coating on galling resistance of threaded oil-casing couplings

• A high-concentration nano-copper ethanol colloid was made by the author.
• A nanoparticulate anti-friction (NPAF) coating was made based on the colloid.
• The field experiments of NPAF on oil casing couplings were tested.
• The NPAF showed that the make-up torque of oil casing couplings can be greatly reduced.

Copperized oil-casing couplings exhibit excellent galling resistance, but owing to economic and environmental issues, there are limited techniques available for copperizing surface treatments. The use of a nanoparticulate anti-friction (NPAF) coating is presented here as a feasible alternative solution. A NPAF coating was fabricated by mixing nano-polytetrafluoroethylene (nano-PTFE) and polyacrylic resin with a high-concentration nano-copper ethanol colloid. The nano-copper ethanol colloid, which was prepared by a patented liquid-phase reduction method, has a nano-copper particle concentration of concentration from 14 to 20 wt%. The average particle size D50 of the nano-copper is about 95 nm. The NPAF coating was successfully used on the surface of threaded oil-casing couplings, which showed clear improvement in friction- and wear-reduction. The field experiments showed that the make-up torque was greatly reduced after using the NPAF coating on the knuckle-thread and buttress-thread casing couplings. The galling resistance of oil-casing couplings was also greatly improved.

The comparison of make-up torque of NPAF coating samples at different positions.From Fig. 5, four NPAF coatings had greatly reduced the make-up torque. At the middle position, because the friction between thread was not too high, the make-up torques corresponding to the specimen 1#, 2#, 3#, and 4# were reduced about 2.70%, 3.93%, 3.18%, and 4.02% respectively. With the increasing of rotations, the friction between thread was also increased rapidly. When arriving at the vertex positions, the make-up torque reached its extreme value. The more of the increasing of rotations, the more effective of the NPAF coating. The maximum make-up torque was reduced about 20.19%, 24.85%, 21.40%, and 24.65% respectively.Figure optionsDownload as PowerPoint slide