Abstract
A study was completed in which the sulfide-stress cracking (SSC) resistance of weld repairs in A487-9Q and CA-15, two commonly used wellhead alloys, was evaluated. The SSC resistance of weld repairs in the as-welded condition was grossly inferior to that of the unrepaired casting. Poor SSC resistance of the repairs was attributed to high hardness in the heat-affected zone. Stress-relieving at 593°C (1100°F) was only marginally effective in reducing hardness and improving SSC resistance. Stress-relieving at 649°C (1200°F) and 704°C (1300°F) produced significant reductions in hardness and improvements in SSC resistance. In these stress-relieved conditions, the SSC resistance of the A487-9Q weldments exceeded that of the unrepaired base metal. However, the SSC resistance of weld repairs in the CA-15 alloy, although improved after post-weld stress-relief heat treatments, was still not equivalent to the SSC resistance of the unrepaired base metal. The only post-weld heat treatment that produced the same level of SSC resistance in the weld repair as in the unrepaired base metal employed austenitization at 982°C (1800°F) and tempering at 704°C (1300°F). The microstructure in the heat-affected zone of the weld repair, even when stress-relieved, was more susceptible to SSC than the base metal in a non-repaired component.
