A threaded coupling in the production tubing string in an oil well at a tension leg platform in the Gulf of Mexico failed in June 1999. T h e coupling was a 110 grade, 15Cr martensitic stainless steel. The fracture was longitudinal, through-wall, the entire length of the coupling, and intergranular.

Neither harm to personnel nor release of hydrocarbons to the environment occurred because of this failure.

This paper presents and discusses the results of a laboratory failure analysis from which it was determined that the fracture was caused by the heat treatment. The fracture was not caused by the production environment or by any other well-bore fluids. The fracture mode was duplicated in unused product in the laboratory. The QA/QC in place for the order did not detect this problem.

Subject
Scanning electron microscopy, Materials, Couplings, Fracture surfaces, Intergranular cracking, Tubing, Mechanical failure, Heat, Fracture, Hardness, Grain boundary, Heat treatment, Toughness
Keywords:
Martensitic stainless steel, 15Cr, UNS $42500, failure analysis, brittle fracture, intergranular cracking, heat treatment, production, tubing, coupling
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
GOV
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