A New Welding Material for Improved Resistance to Ductility Dip Cracking

Nickel-Chromium-iron alloys and welding products have been used throughout the life of the nuclear welding industry. From the beginning, Welding Electrode 182 and Filler Metal 82 were used to weld alloy 600 until they were found to be susceptible to primary water stress-corrosion-cracking (PWSCC). This brought about the need for a 30% Cr-containing alloy 690 along with Welding Electrode 152 and Filler Metal 52. These materials were resistant to PWSCC, but the welding products were found to be susceptible to ductility dip cracking (DDC). Because DDC is a solid state cracking phenomenon that may occur in highly restrained austenitic welds, most of the existing tests were ineffective for measuring DDC. The Ohio State University welding group introduced the Strain-to-Fracture (STF) test to measure the tendency for DDC. A number of nuclear welding materials have been subjected to STF testing and a new nickel alloy material with 30% chromium, INCONEL (R) FM52MSS, has shown substantially improved DDC cracking resistance when measured with the STF test. This paper discusses the development and performance of the welding material and the results of STF test of this new alloy.