Abstract
During the welding of 690 nickel-based alloy, solidification cracking (SFC) and ductility-dip cracking (DDC) easily forms, which has a negative effect on the quality of welded joints and service life. The present study examined the effects of welding heat input and cladding layers on the SFC and DDC, as well as their formation mechanism. The microstructure observation, elemental distribution, and Varestraint test were carried out. The results show that SFC and DDC were formed for the Inconel filler metal 52M, and SFC is more prone to form than DDC. The alloy elements such as Fe, Si, C, and P from base metal can expand the solidification temperature range, such that the SFC sensitivity increases. With the increase of welding heat input, the grain size of cladding metal is increased with a great SFC sensitivity. The increasing welding heat input also makes DDC possible due to the formation of a large angle grain boundary.
Highlights
Hot cracking is a fatal defect for the Ni-based alloy during weld overlay [15,16], which is generated at a high temperature during cooling after welding or during reheating via subsequent welding [17]
The results showed that hot cracking occurred near the fusion boundary when the 308L was cladded to the buffer layer of Inconel 52
F304LN base metal melts were melted in the weld during the welding process, resulting in a dilution in the weld composition, which had an effect on they were introduced into the weld with the dilution of the base metal
Summary
Many studies have been carried out on the hot cracking of Ni-based alloys during weld overlay [18,19]. Rapettia et al [21] studied the effect of composition on DDC of 690 nickel alloy during multi-pass welding. They found that the cracks observed in this study resulted from DDC, not from liquation or SFC. The evolution and controlling of cladding metal formation, microstructure, and DDC is studied, as well as the effect of welding parameters, thermal boundary conSFC, and DDC is studied, as well as the effect of welding parameters, thermal boundary ditions, and impurity elements on SFC and DDC.
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