| YIN Qi-shuai,YANG Jin,LI Zhen-kun,CHUAI Guang-shan,SHEN Guo-hua,YANG Fu-gui,SONG Yu.Effect of Airless Spray MoS2/Cu/C Composite Coating on Buckle-resistant Performance of Offshore Pipe String Threads[J],51(5):24-31 |
| Effect of Airless Spray MoS2/Cu/C Composite Coating on Buckle-resistant Performance of Offshore Pipe String Threads |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.05.003 |
| KeyWord:MoS2/Cu/C composite coatings airless spraying thread anti-galling drill string tubing and casing offshore drilling and completion |
| Author | Institution |
| YIN Qi-shuai |
China University of Petroleum Beijing, Beijing , China |
| YANG Jin |
China University of Petroleum Beijing, Beijing , China |
| LI Zhen-kun |
Engineering Technology Branch of CNOOC Energy Development Co., Ltd., Tianjin , China |
| CHUAI Guang-shan |
CNOOC Enertech Equipment Technology Co., Ltd., Tianjin , China |
| SHEN Guo-hua |
CNOOC Enertech Equipment Technology Co., Ltd., Tianjin , China |
| YANG Fu-gui |
ZS Titanium Co., Ltd., Liaoning Dandong , China |
| SONG Yu |
China University of Petroleum Beijing, Beijing , China |
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| Abstract: |
| Threaded pipes deliver offshore oil or gas under high pressure. Thus, threaded connections must be gas or liquid tight in the severe offshore environment. Uneven force or deformation on the surface of the thread tooth will cause galling and even lead to thread failure. Galling is the key that affects the safety and life of the pipe strings and restricts the quality and efficiency of offshore drilling and well completions. In addition, environmental protection has become the primary concern in recent years. This paper aims to innovatively prepare MoS2/Cu/C composite coatings using a non-polluting airless spray coating technology to improve the anti-galling performance of the threads of the offshore pipe strings. MoS2/C coating is a well-known solid lubricant that can reduce drag. Further, nano-scale Cu powder has good thermal conductivity. The prepared MoS2/Cu/C composite coatings provide a thin layer of heterogeneous composite materials with good thermal conductivity, and excellent friction reduction on the thread surface of the offshore pipe strings. The MoS2/Cu/C composite coatings are prepared by doping MoS2/C coating with nano-scale Cu powder and adopting airless spraying and high-temperature curing. Properties of the composite coatings, including microstructure, microhardness, and friction coefficient, are evaluated first. Then, the morphology of the prepared MoS2/Cu/C composite coatings is analyzed by scanning electron microscopy. Finally, make-up and breakout tests are conducted on the pipe string samples with the prepared MoS2/Cu/C composite coatings to test their anti-galling performance. As a result, the semi-molten powder is superimposed and deposited multiple times during airless spraying and high-temperature curing, forming a dense structure without apparent pores. Besides, sandblasting pretreatment of MoS2/Cu/C composite coatings significantly improved the uniformity and adhesive strength of the coatings. Moreover, the coatings and the metal substrate are tightly combined in a zigzag shape. The hardness of the metal substrate does not change before and after sandblasting and airless spraying. The MoS2/Cu/C composite coatings formed a smooth protective film on the thread surface and had no detrimental effect on the metal substrate. The friction coefficient of the thread surface is reduced. The make-up torque is reduced by 19% to 23%. In conclusion, doping nano-scale Cu powder in MoS2/C coating to form MoS2/Cu/C composite coatings effectively reduce the friction coefficient of the thread surface without reducing the strength of the metal substrate. The MoS2/Cu/C composite coatings obtained by airless spraying and high-temperature curing can effectively improve the anti-galling performance of the threads of the offshore pipe strings. Pipe strings with the prepared MoS2/Cu/C composite coatings have been successfully applied to offshore drilling and well completions. The prepared MoS2/Cu/C composite coatings turn out to prolong the life of the pipe strings and enhance the efficiency of offshore drilling and well completions, saving a substantial amount of money for the oil and gas industry. Overall, the technology presented in this paper has excellent reference significance and is recommended for offshore drilling and well completions. |
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