Research on Vacuum Brazing of 40Cr Steel with YG8 Hard Alloy

The vacuum brazing of 40Cr steel to hard alloy YG8 with CuMnNi brazing filler metal is investigated.The influence of brazing temperature and the interlayer thickness on the joint's strength is studied.The optimal process parameters are determined through the three-point bend test.The microstructure is observed by the SEM,and the CuMnNi filler's diffusion in the base metal is also analyzed through the energy spectrum analysis.Through the comparison of the wetting angle of the brazed filler metal spreaded onto 40Cr steel and the hard alloy YG8,the bonding properties of the brazed filler metal with the base metal are discussed.Experimental results show that Ni interlayer and the base metal are well joined with filler metal.No crack is found in the brazed joint,and the bonding strength is improved when the thickness of Ni interlayer is 0.2 mm and the brazing temperature at 1 020 ℃.