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 800Hrnpigtails from a steam reformer furnace. Typically, cracks on pigtails occur circumferentially due to highrnbending stresses in the bends, or at welded connections. However, in present samples, longitudinalrncracks were found on the pigtails. Metallurgical evaluation revealed that the pigtails had cracked fromrnboth ID and OD as a result of intergranular stress oxidation cracking. This failure mechanism resultsrnfrom the combination of intergranular creep crack growth from repeated loading and high temperaturernoxidation. Our metallurgical observations are consistent with a common failure mechanism reported forrnalloy 800H.