Study on filler metal (Ni-Fe-C) during GTAW of WC-30Co to 45″ carbon steel

In this study, WC-30Co cemented carbide is welded to carbon steel by the gas tungsten arc welding (GTAW) using Ni-Fe filler metal and Ni-Fe-C filler metal. The butt joints manifest more embrittling η-phase carbides with Ni-Fe filler metal, while less even no η-phase carbides with Ni-Fe-C filler metal. The η-phase carbides morphology and formative factors were further discussed using Backscattered Electron Imaging (BEI) method; Electronic probe microanalysis (EPMA) is used to determine the distribution of elements Ni, Fe, C, W and Co across the HAZ (Heat Affected Zone) near WC-30Co/welded-seam interface. The hardness profile is determined using micro-hardness measurements and bend strength value of butt joint with different filler metal is tested by four-point bend strength test. The hardness profile and bend strength value agree with the information obtained from microstructure analysis, BEI analysis and X-rays phase analysis very well. The results show: (1) butt joint of WC-30Co/carbon steel can be obtained using GTA with Ni-Fe-C filler metal; (2) the addition of carbon content to Ni-Fe filler metal leads to less even none η-phase multi-carbides strongly, and mechanical property of butt joint can be improved.