Failure Mechanisms of Alloy 800H in Steam Reformer Furnace Pigtails

摘要

This paper will discuss the results of an investigation into cracking that occurred on alloy 800H pigtails from a steam reformer furnace. Typically, cracks on pigtails occur circumferentially due to high bending stresses in the bends, or at welded connections. However, in present samples, longitudinal cracks were found on the pigtails. Metallurgical evaluation revealed that the pigtails had cracked from both ID and OD as a result of intergranular stress oxidation cracking. This failure mechanism results from the combination of intergranular creep crack growth from repeated loading and high temperature oxidation. Our metallurgical observations are consistent with a common failure mechanism reported for alloy 800H.