Research On Vacuum Brazing Of Steel16Mn And Hard Alloy YG6C

In this paper, the vacuum brazing of steel16Mn and hard alloy YG6C with self-madeCuMnNi filler metal was studied. The melting temperature range was tested by DTA method.Through three-point bending experiment, wetting test, SEM and EDS, the effects of vacuumdegree, different brazing temperature, joint clearance and thickness of Fe interlayer onmicrostructure and properties of the joint were discussed respectively, and the best processparameters could be found.Vacuum degree has a great impact on the wetting properties. In the condition of middlevacuum, the CuMnNi filler metal can not be wet on both YG6C and16Mn steel; but in thecondition of high vacuum, The CuMnNi filler metal in the base metal has good wettabilityin brazing process and on the wetting properties of the steel16Mn is better than hard alloyYG6C. With the rising of temperature, the wetting angle decreases and the wettability getsbetter and better.The brazing temperature is the most important process parameters in the vacuumbrazing process. When the temperature is too low, the element diffusion ability is weak andInterface metallurgy combined is poor, so the strength of joints is low; with the rising oftemperature, the diffusion of Ni and Fe, and Co elements exacerbate. The hardness andfragility of the reaction products increase, but the strength of joints is lower. In thetechnology parameter: brazing temperature is950℃and clearance is0.2mm, the bendingstrength is best which reaches to709MPa.The brazing clearance also has a great influence on the strength of joints. When theclearance is too big or too small, the strength of joints can be influenced. When the brazingclearance is too small, the distance of Fe and Co elements diffusion is small and much morethe reaction product can be formed. More brittle reaction products make strength of jointslow; when the clearance is too big, the distance of Fe and Co elements diffusion increases,and it can’t form good metallurgical combination. When the brazing clearance is too wide,capillary action of brazing seam decreases and filler metal is easy to drain, and it is difficultto fill the gap brazing seam, which can appear empty, so the joint strength decreases. Thebest bending strength is got when joint clearance is0.2mm.Add different thickness of Fe interlayer can not improve the strength of the joints.Because of the Fe interlayer hinders the diffusion of elements, the reaction product of interfacial region is less. Therefore, bending strength of the joint is affected and theperformance of the joint is poor.