The Effect of Nozzle Safe End Hot/Cold Wire Tungsten Inert Gas Buttering on Microstructure and Property

Abstract

Hot wire tungsten inert gas (HWTIG) and cold wire tungsten inert gas (CWTIG) have been used for nozzle safe-end buttering of nuclear island critical equipment, the effect of the HWTIG and CWTIG buttering on microstructure and property has been investigated. Research results revealed that the grain orientation of HWTIG buttering layer is mostly concentrated in (0 0 1) direction and the average grain size is 118.375μm, while the grain orientation of the CWTIG dispersed distribution in (0 0 1), (1 1 1) and (1 0 1) direction, and the grain size is 158.479μm. Furthermore, the grain boundary misorientation angle of HWTIG buttering layer has higher occurrence frequency between 10° and 30° high-angle boundary, whereas the CWTIG has higher occurrence frequency within 30° and 60°. Moreover, the microstructure of HWTIG buttering layer has less chromium-rich M23C6-type carbide compared to CWTIG, and the M23C6-type carbides discontinuous distribution on the grain boundary of HWTIG buttering layer. The buttering layer of HWTIG has lower ductility-dip cracking sensitivity than CWTIG.