Development of a Chromium-Free Consumable for Austenitic Stainless Steels—Part 1: Monel (Alloy 400) Filler Metal

During fusion welding of stainless steels and other high-Cr alloys, evaporation and oxidation of Cr from the molten weld pool result in the generation of carcinogenic hexavalent chromium (Cr[VI]) in the welding fume. Stringent new exposure limits from the Occupational Safety and Health Administration (OSHA) might limit the environment in which the welding of stainless steel will be possible in the future. Therefore, a Cr-free filler metal is needed to reduce the release of Cr(VI) during the welding of stainless steel. From the galvanic series, the corrosion potential of the Ni-Cu alloy K400 (UNS N04400) is located in the same potential range as Type 304 (UNS S30400) and Type 316 (UNS S31600) stainless steels. In this study, the applicability of the Monel-type filler metals for the welding of austenitic stainless steel is examined. Type 304L (UNS S30403) stainless steel plate was successfully welded with Monel filler wire, resulting in high-quality welds with no cracks. The welds survived long-term exposure to mildly aggressive environments like 0.1 M sodium chloride (NaCl) with no evidence of corrosion. However, Cu-rich regions in the weld were the weak spots for corrosion susceptibility.