Microstructure transformation and crack sensitivity of WC-Co/steel joint welded by electron beam

The 30 mm thick WC-Co cemented carbide and AISI 1045 steel were electron beam welded (EBW) with and without Ni-based filler metal. Welding-brazing joints of WC-Co and steel were obtained as the molten pool wet and spread on the unmelted WC-Co base metal. The WC loose areas formed at the WC-Co interface have guaranteed the effective metallurgical bonding. According to simulation results, the thickness of filler metal should be less than 1 mm to avoid unbonding. The direct EBW WC-Co/steel joint was mainly composed of martensite, residual austensite and herringbone M₆C carbides. The bulk brittle phases η-Fe₃W₃C increased the joint brittleness and crack sensitivity. With Ni-based filler metal, the microstructure of the joint was mainly composed of γ-Fe and herringbone carbides FeW₃C. No η-Fe₃W₃C formed at WC-Co interface because of the metallurgical blocking effect. The plastic property of the joint was improved, and WC-Co/filler metal/steel EBW joints with no crack were obtained.