Abstract
W-Cu composite and 1Cr18Ni9 steel were brazed with Ni-based amorphous filler metal in a vacuum furnace. Four-point bending strength, fracture morphology, microstructure and elements distribution were studied by a series of standard methods. Then the influence of brazing clearance on microstructure and properties of the brazed joint were analyzed and discussed. Results indicated that, within the scope of the selected parameters, bending strength of the brazed joint increased significantly as reducing the brazing clearance. While the brazing clearance controlled to be 20 μm, the four-point bending strength performed the largest value, up to 333 MPa. The joint fracture showed a typical ductile fracture characteristics. Microstructure of the brazing seam was mainly composed of γ-Ni solid solution, W-Ni solid solution, CrB, and a part of eutectic phases of Ni₃Si and Ni3B. The microstructure of brazed joint with brazing clearance 20 μm was more uniform and more stable. Microstructure and element of brazed joint almost transformed into single-phase solid solution. Meanwhile micro holes disappeared and the amount of brittle phases reduced, which provided well plastic reserves for the brazed joint.

Key words
W-Cu composite, brazing clearance, microstructure, fracture, bending strength

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