Integrity of internally coated premium connections

A research project was established for developing highly corrosion-resistant oil country tubular goods with thin layers on their inside surfaces. This report studied the integrity of internally coated joints as a premium connection, which was verified by anti-galling, sealability, and full scale SSC tests. Pin was coated with Plasma Transferred arc hardfacing (PTH), Ion plating, Plasma CVD, or Planer magnetron sputtering process (PMSP), while coupling was done with PTH, or Cylindrical magnetron sputtering process (CMSP). Coating material was TiN (titanium nitride) or UNS N10276. Anti-galling properties were studied by twenty-time Makeup/Breakout tests. Sealability was studied with a dedicated thermal-cycle-tester under thermal-cycling with internal pressure and tension, and static combined loads of internal pressure, tension, and bending. Full scale SSC test was carried out under the condition of 200 C-1.1 MPa H{sub 2}S-1.5MPa CO{sub 2}-20%NaCl. Final selected coatings were as follows. Coating material was UNS N10276. The processes for pin were PTH for inside surface, and PMSP for threads, respectively; those for coupling were PTH for inside surface and CMSP for threads. No galling, no leak, and no corrosion attack were observed in the established connection.