The Effect of Carbon Content in Filling Alloys on η Phase Formation in the Interface Zone of YG30 and Weld Bead
The cemented carbide YG30 and steel 1045 were welded with Co-Fe-C filling alloys with different carbon contents by the tungsten-inert-gas (TIG) arc welding. η phase formation at the welding joints was investigated through scanning electronic microscopy (SEM). The results show that the average composition of η phase is W-25, Fe-22, Co-19, C-24 (mass, %), which is a kind of carbide enriched by Fe, W，and Co. The amount of η phase formed near the interface of YG30 and weld bead is related to the C content in the filling alloy. Namely the amount of η phase decreases with the increasing of the C content in the filling metal. When the C content reaches to 0.8 wt%, no η phase forms. The reason of which is that the added C reduces and/or restrains the resolving of the WC that locates at the interface, so that inhibit the W and C to form η phase with Fe and Co. The existence of large-size η phase near the interface is mainly attributed to the aggregation of small size η phase with the unsolved WC due to the stir of liquid metal, and then growing up.
Zhengyi Jiang, Shanqing Li, Jianmin Zeng, Xiaoping Liao and Daoguo Yang
X. J. Zhao et al., "The Effect of Carbon Content in Filling Alloys on η Phase Formation in the Interface Zone of YG30 and Weld Bead", Advanced Materials Research, Vols. 189-193, pp. 3309-3312, 2011