Solidification Behavior and Weldability of Dissimilar Welds Between a Cr-Free, Ni-Cu Welding Consumable and Type 304L Au
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GOVERNMENT regulations in the United States and elsewhere are decreasing the allowable exposure levels of hexavalent chromium (Cr VI) to weldingrelated personnel. Achieving these reduced exposure levels may not be practical from an engineering controls standpoint during stainless steel component fabrication in tightly enclosed locations. Such applications include the inside of ship hulls and pressure vessels. One method of addressing this problem is the implementation of a chromium-free welding consumable that provides equivalent mechanical performance and corrosion characteristics to those exhibited by current stainless steel welding consumables. Consumable development research has shown that a Ni-Cu welding consumable, with noble alloying additions of either Pd or Ru, may be suitable for this purpose.[1–6] The corrosion of dissimilar welds is typically controlled by galvanic interactions. The current study was part of a larger effort investigating alloys JEFFREY W. SOWARDS, formerly Graduate Research Assistant, with the Welding & Joining Metallurgy Group, The Ohio State University, Columbus, OH 43210, is now Metallurgist, with NIST, Boulder, CO 80305. Contact e-mail: jeff[email protected] DONG LIANG, formerly Graduate Research Assistant, with the Fontana Corrosion Center, The Ohio State University, is now Project Engineer, with DNV, Columbus, OH. BOIAN T. ALEXANDROV, Research Scientist, and JOHN C. LIPPOLD, Professor, are with the Welding & Joining Metallurgy Group, The Ohio State University. GERALD S. FRANKEL, Professor, is with the Fontana Corrosion Center, The Ohio State University. Manuscript submitted March 9, 2010 Article published online October 26, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
from the Ni-Cu metallurgical system for use as a welding consumable because they are galvanically compatible with Type 304 stainless steel in seawater. However, when switching from a commonly used welding consumable that solidifies under primary ferrite solidification mode (such as the filler metal E308L) to one that solidifies as austenite, weldability may be affected adversely, particularly with respect to weld solidification cracking.[7] The weld solidification cracking susceptibility of Ni-base alloys is typically higher than Type 304L/308L stainless steel as a result of the fully austenitic solidification mode.[7–9] Previous research has shown that MONEL* consum*MONEL is a registered trademark of the Special Metals Corporation, Huntington, WV.
ables (nominally 70Ni-30Cu; Special Metals Corporation, Huntington, WV) may be used to weld stainless steel without any adverse weldability issues as long as the proper weld practice is followed.[10–13] Based on the reviewed literature regarding dissimilar metal welding of Ni-Cu consumables with stainless steel, composition is the most important factor that must be considered in evaluation of the weldability performance. Dilution of the welding consumable with the base metal can alter the weldability with regard to solidification and liquation cracking, porosity formation, wel
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