Microstructure and properties of W-Cu/1Cr18Ni9 steel brazed joint with different Ni-based filler metals

Abstract W-Cu alloy and 1Cr18Ni9 steel were brazed with NiCrSiBFeTi and NiMnSiCuZr filler metals in a vacuum furnace. The main microstructure of the NiCrSiBFeTi brazing seam region was a Ni-based solid solution of W, Cu, Cr, and Fe dissolved in the Ni phase and intermetallic compounds CrB and TiCr ₂ . The main microstructure of the NiMnSiCuZr brazing seam region was a Ni-based solid solution of Cu, Cr, and Fe dissolved in the Ni phase Fe-based solid solution of Ni, Cu, and Cr dissolved in the Fe phase and intermetallic compounds Mn ₅ Si ₃ , Ni ₃ Si, and Ni ₇ Zr ₂ . The elements Ni, Si, and Ti contained in the NiCrSiBFeTi filler metal and the elements Ni, Mn, and Si contained in the NiMnSiCuZr filler metal were more easily diffused into the interface of W-Cu alloy compared with that of 1Cr18Ni9 steel. The shear strength values of NiCrSiBFeTi joint and NiMnSiCuZr joint were approximately 285 and 249 MPa, respectively, and fracture of the two joints occurred at the interface near the W-Cu alloy side. The fracture morphology of the former was identified as cleavage brittle fracture, and the latter was identified as intergranular brittle fracture.