Reaserch On Bonding Interface Morphology And Properties Of YG10/40Cr Joints

Cemented carbide with high strength, high hardness and good corrosion resistance, widely used in cutting tool, wear-resistant parts, mining and road engineering machinery and other fields. However, cemented carbides exhibit great brittleness, making it difficult to produce large size, complex shape products. Therefore, the joining between hard alloy and steel has practical value to expand the application scope of cemented carbide. In this article, WC-Co and steel were connected by means of partial transient liquid phase bonding and current assisted diffusion bonding, respectively. The microstructure of joint, phase composition and distribution regularity of interface elements were evaluated by scanning electron microscopy(SEM), X-ray spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS), respectively. The shear strength of joints was evaluated by universal testing machine and the fracture model of the joints was analyzed by combining the SEM and EDS.Ti/Ni/Ti was selected as interlayer system, and the partial transient liquid phase was used to prepare the YG10/40 Cr bonding. The results indicated that:(1)when the bonding temperature was 950℃~1100℃, the joint strength was increased first and then decreased with the temperature increased; joint strength came to maximum value at 1000℃, the value was 137 MPa, the fracture mode of the joint was across-interface mixed fracture; with the temperature increased, the reaction layer Ni3 Ti was overgrown, which reduced the interface bonding strength; the gradient layer combination interface structure of WC-Co/(TiC+WC) transition layer/TiNi3/Ni(Ti)solid solution/Ni was formed between YG10/interlayer; the gradient layer combination interface structure of TiC/TiNi3/Ni(Ti)solid solution/Ni was formed between interlayer/40Cr;(2)the thickness of interface fragile reaction layer Ni3 Ti was increased gradually and the joint strength was increased first and then decreased in the case that the brazing time was increased from 1h to 7h at 1000℃, which indicated that there was an optimum value for the thickness of interface reaction layer, and if the thickness of interface reaction layer was greater than this value, the joint shear strength was decreased drastically.Ni was selected as interlayer and the plasma activated sintering technique was used to realize the rapid diffusion bonding of YG10/40 Cr. The results showed that:(1)the joint strength was increased gradually with the brazing temperature increased(680℃~750℃)in the case that the bonding time was 13min; the joint strength was increased gradually with the holding time(6min~13min) extended on occasion that the brazing temperature was 750℃;(2)the roughness of surface of substrate showed an obvious influence on joint bonding strength, with the descent of roughness, the joint strength was increased; in the case that the roughness of YG10 was 0.677μm, the maximum joint strength was 201.89MPa;(3)the thickness of the interlayer Ni showed an influence on the distribution of residual stress, thus influence the joint strength; with the increase of thickness of Ni layer, the shear strength of joint was decreased continually; the maximum joint strength was 293.07 MPa in the thickness of 50μm.