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Abstract
Effects of ER308L buffer layer and welding parameter slope down time on the hot cracking susceptibility of alloy 52M overlay on CF8A base metal were studied. The results indicated that Si segregation was a critical factor affecting Alloy 52M hot cracking. Applying ER308L buffer layers between CF8A and Alloy 52M can reduce the dilution of Alloy 52M weld beads and minimise the contribution of Si from CF8A into Alloy 52M, thereby alleviating Si segregation and the hot cracking susceptibility of Alloy 52M. When the Si content in the grain boundary region was lower than 0·81 wt-%, the hot cracking in the weld bead could be mitigated completely. In many cases, crater cracks occurred in the end crater of the weld bead. Increasing the number of ER308L buffer layers and extending the slope down time could reduce crater crack susceptibility. However, the Si content in the grain boundary region should be controlled to be lower than 0·63 wt-% to prevent crater cracking.