The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds

Min-Yi Chen,Leu-Wen Tsay,Sheng-Long Jeng,Tai-Cheng Chen,Tai-Jung Wu

doi:10.3390/met9060651

Min-Yi Chen, Leu-Wen Tsay + Show 3 more

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https://doi.org/10.3390/met9060651

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Abstract

Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the structures were identified by electron backscatter diffraction (EBSD). The hot cracking of the overlay welds was related to the microconstituents at the interdendritic boundaries. The formation of γ-intermetallic (Ni3(Nb,Mo)) eutectics was responsible predominantly for the hot cracking of the 52M and 52MSS overlays. The greater Nb and Mo contents in the 52MSS overlay enhanced the formation of coarser microconstituents in greater amounts at the interdendritic boundaries. Thus, the hot cracking sensitivity of the 52MSS overlay was higher than that of the 52M overlay. Moreover, migrated grain boundaries were observed in the 52M and 52MSS overlays but did not induce ductility dip cracking (DDC) in this study.

Highlights

Stress corrosion cracking (SCC) is a major concern in high temperature water environments, which are commonly found in water reactors and piping systems in nuclear power plants [1,2,3,4]
The results indicated that hot cracks were more likely to be seen in directly onto the CF8A substrate
The results indicated that hot cracks were more likely to be seen in the ending craters, especially those of the 52MSS welds

Summary

Introduction

Stress corrosion cracking (SCC) is a major concern in high temperature water environments, which are commonly found in water reactors and piping systems in nuclear power plants [1,2,3,4]. IN52, 52M, and 152 alloys are widely used as the filler metals for the overlay-welding of different components to alleviate SCC damage in those dissimilar welds [6,7]. Decreasing the dilution rate of a dissimilar weld will be an effective way to mitigate hot cracking of 52M overlays [19,20]. In practical application, depositing proper buffer layers before a 52M overlay is applied decreases the number of hot cracks in the welds [21,22]. An increase in Nb and Mo contents increases the size and Metals 2019, 9, 651; doi:10.3390/met9060651 www.mdpi.com/journal/metals

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Discussion

Conclusion