Comparison of the microstructure of ERNiCrFe-7A deposited metal by cold wire GTAW and hot wire GTAW

Abstract

ERNiCrFe-7A filler metal is widely used for welding Inconel 690 alloy, which is often considered for fabricating key components such as reactor pressure vessel and steam generator of nuclear island main equipment. In this work, ERNiCrFe-7A deposited metal was prepared by cold wire and hot wire GTAW process separately. The microstructure and mechanism of precipitation of deposited metal were studied by OM, XRD, SEM, and TEM. Results show that both cold wire and hot wire GTAW can get good quality of ERNiCrFe-7A deposited metal. The matrix of deposited metal is γ-austenite. The microstructure of deposited metal has a cellular dendritic characteristic. The intragranular precipitates are MX phases (M = Nb and Ti, X = C and/or N), and the intergranular precipitates are Cr-rich M23C6 phases. The heat input of cold wire GTAW is higher than that of hot wire GTAW, the columnar grains by cold wire GTAW are wider than those of hot wire GTAW, and the number of MX and M23C6 phases by cold wire GTAW is more than that by hot wire GTAW.