The Experimental Research On Brazing Welding Process And The Joint Properties Of YG8 Cemented Carbide

The characteristics and industrial applications of cemented carbide were summerized in this paper, and the main problems in cemented carbide welding were analyzed, some welding methods that may be used on cemented carbide, its procedure factors as well as its updated research results were reviewed, including brazing,diffusion welding,gas tungsten arc welding, laser welding, electron beam welding and so on, the forwarding problems to be researched were pointed out as well.The brazing process and joint of cemented carbide and 45 steel were investigated,including the compare of gas brazing and furnace brazing,the choice of brazing alloy and flux and the influence of heat treatment. To find out the quality difference between domestic and import product, the microstructure of joints was investigated with optical microscopy, Vickers-hardness was measured by Vickers ,mechanical properties were tested by standard tensile tests on small-scale specimens, fractography characteristics were observed and analized,chemical components were analized by scanning electron microscopy (SEM), Meanwhile, the reasons that causing macroscopical and microcosmic defects, and the prevention measures in the braze welding process of cemented carbide were discussed.The results show that good surface welded joints can be got under proper matching of welding parameters.The interface between brazing seam and cemented carbide is smoother than the other side in the microstructure of joints.Elements of cemented carbide barely diffuse into brazing seam except C during the brazing process.The brazing alloys diffuse little into the base metal and mainly distribute in the seam.Heat treatment has a little influence on the microstructure and hardness of the joints,but can release the residual stress effectively.The shearing stength of the joints are lower than 200 MPa,it could be the effect of residual stress and any other force during the experiment. Tensile fracture of joints usually occurs near the cemented carbide.The morphology of fracture is ductile and brittle mode.Some cracks occur in the fracture which showed high residual stress in the welding. The common welded defects in the joints are oxide slag,ηphase, cracks, etc.The main cause of the poor performance of domestic product could be the unreasonable design of the brazing seam,which easily result in some welded defects such as incomplete fusion and oxide slag during the manufacture and reduce the practical carrying capacity of the joints.Moreover,the brazing alloy used in the import product could be some kind of tailor-made high strength Cu-based brazing fillier metal.