CRACKING IN WELDS OF HEAVY-WALL NICKEL ALLOY PIPING DURING FABRICATION

摘要

Alloy 800HT (UNS N08811) and Alloy 617 (UNS N06617) are widely recognized as having highsusceptibility to reheat cracking (also referred to as relaxation cracking or stress relief cracking).However, in a recent cracking case in heavy-wall Alloy 800HT piping during fabrication, the crackingwas found in weld metal of ENiCrCoMo-1 (UNS W86117: welding electrode for shielded metal arcwelding) only, while no cracking was found in the HAZ of Alloy 800HT or the weld metal ofERNiCrCoMo-1 (UNS N06617: filler metal for gas tungsten arc welding). This paper firstly presentsinvestigations into the recent cracking case in the circumferential weld metal of heavy-wall Alloy 800HTpiping. Then, the high temperature tensile properties of Ni base welding consumables, which aregenerally used for Alloy 800HT welding, are described. Cracking in service is outside the scope of thispaper. This paper also offers several recommendations to mitigate the risk of cracking duringfabrication.