SCC Behavior at Alloy 52M-182 Weld Overlay Interfaces in a PWR Environment

摘要

Weld overlays (WOL) of alloys believed to possesssuperior stress corrosion cracking (SCC) resistance dueto their higher Cr content are typically applied over weldsmade with SCC-susceptible alloys with the expectationthat they will act as a barrier to SCC. The objective ofthis work is to investigate the behavior of a crack initiatedin Alloy 182 as it approaches the Alloy 52M WOL. Forthis purpose, several Alloy 52M WOLs deposited on Alloy182 welds were tested in simulated primary waterenvironment. Testing revealed that the SCC crack growthrates (CGRs) in Alloy 182 ahead of the interface weremoderate, or were found to decrease substantially aheadof the interface. In all cases, the crack advanced fromAlloy 182 into Alloy 52M to varying degrees, dependingprimarily on the Cr dilution of the first Alloy 52M layers.This cracking can substantial, yielding SCC CGRs ratesof 10~(-10) m/s in the first few weld layers. Crack deflectionalso occurred at the interface between the two alloys,primarily in cases where Alloy 52M WOL appearedresistant.