Evaluation of Sulfide Stress Cracking Susceptibility of Welded Joints of Supermartensitic Stainless Steel Used in Oil Country Tubular Goods (OCTG)

Mandrels for chemical injection are used in the production column of oil and gas wells, a complex system below the Christmas tree, also known as oil country tubular goods. The exploration in the deep water and sub-salt layer brought new problems, such as the increase of the aggressiveness of the transported fluids. Supermartensitic stainless steels (SMSSs) are used to construct mandrels, and the fabrication processes include the joining of forged and seamless tubes by welding. Even containing much less carbon than traditional martensitic stainless steels, the welding of SMSSs requires attention. In this work, the microstructure and sulfide stress cracking resistance of welded joints of a mandrel were analyzed. The objective was to evaluate whether other mandrels from the same supplier can be put into service in mid-sour environments. The results show that even being heat-treated after welding, the weld metal has poor resistance to sulfide stress cracking, and this can be attributed to the excessive hardness of the WM and also to the presence of welding defects (pores).