Electron beam welding-brazing of hard alloy to steel with Ni-Fe intermediate

The direct welding of hard alloy to steel by electron beam was carried out. The weld was mainly composed of molten steel. The microstructure of joint mainly consisted of the cellular dendrites and the eutectic phases. A transition layer enriched with large amounts of carbides formed at the interface of hard alloy. Finite element analysis of the welding sequence indicated that the maximum residual stress distributed at the weld or the hard alloy base metal where the macroscopic cracks tended to generate. According to the metallurgical compatibility principle, the cracks can be avoided by a powder metallurgy Ni-Fe intermediate during electron beam welding-brazing of hard alloy to steel. The microstructure of the joint was composed of (Fe,Ni) solid solution and carbides. The transition layer enriched with brittle phases did not form at the interface in the hard alloy side. Therefore, the microhardness of the weld was reduced and the compatible deformation ability of the weld was improved, and thus macroscopic cracks could be avoided.