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Effect Of Chromium Dilution On SCC Growth Rate In Inconel Welds

Naval Nuclear Laboratory has developed Alloy 52i, a high chromium (~27 wt%) weld metal that can be welded onto Alloy 600, Alloy 625, or Alloy 690 wrought material. Alloy 52i by itself has shown to be very resistant to SCC in deaerated pure water. However, there is a concern when welding Alloy 52i onto the more SCC susceptible Alloy 82H or Alloy 600 that the first weld bead would be chromium diluted by the mixing with the lower-chromium base metal. This lower chromium level may lead to higher SCC susceptibility than the surrounding weld metal, since chromium content has shown a correlation with nickel alloy SCC susceptibility. In commercial nuclear power applications, many plant components are limited by SCC propagation in welded components within the weld metal; this test program seeks to understand which weld combinations, with respect to chromium concentration, may yield deleterious SCC properties for improved lifetime of plant components.

Product Number: ED22-17109-SG
Author: Ainsley Pinkowitz, David S. Morton, Tyler E. Moss, John V. Mullen
Publication Date: 2022
$20.00
$20.00
$20.00

This test program was designed to evaluate the effect of weld dilution on the stress corrosion cracking (SCC) performance of nickel based weld metals. Tests were performed in deaerated pure water on specimens with controlled levels of chromium, which range from the high chromium weld metal Alloy 52i (exceptional SCC resistance) to the low chromium weld metal Alloy 82H (poor SCC resistance). Chromium content has been shown to correlate with nickel weld SCC susceptibility for Inconel-only welds. Tests were also conducted in specimens from Inconel/Low alloy steel welds. SCC growth rates (SCCGR) for specimens above 21 wt% chromium, which includes Alloy 52i (equivalent to Alloy 152) diluted with Alloy 600 (A600), Alloy 82H (equivalent to Alloy 82), or Alloy 690 (A690) and monolithic Alloy 52i, are one to two orders of magnitude slower than chromium contents below 19 wt%, which includes 8N12 (equivalent to Alloy 182) and Alloy 82H diluted with A600. These results indicate that Alloy 52i weld dilution, associated with Alloy 600 and Alloy 82H welds, does not degrade the SCC performance of Alloy 52i.

This test program was designed to evaluate the effect of weld dilution on the stress corrosion cracking (SCC) performance of nickel based weld metals. Tests were performed in deaerated pure water on specimens with controlled levels of chromium, which range from the high chromium weld metal Alloy 52i (exceptional SCC resistance) to the low chromium weld metal Alloy 82H (poor SCC resistance). Chromium content has been shown to correlate with nickel weld SCC susceptibility for Inconel-only welds. Tests were also conducted in specimens from Inconel/Low alloy steel welds. SCC growth rates (SCCGR) for specimens above 21 wt% chromium, which includes Alloy 52i (equivalent to Alloy 152) diluted with Alloy 600 (A600), Alloy 82H (equivalent to Alloy 82), or Alloy 690 (A690) and monolithic Alloy 52i, are one to two orders of magnitude slower than chromium contents below 19 wt%, which includes 8N12 (equivalent to Alloy 182) and Alloy 82H diluted with A600. These results indicate that Alloy 52i weld dilution, associated with Alloy 600 and Alloy 82H welds, does not degrade the SCC performance of Alloy 52i.