Research On Key Technology Of Brazing Diamond Abrasive With Ni-Cr Alloy In Protective Furnace

Compared with electroplating and sintering diamond tools, brazing diamond tools have the characteristics of achieving chemical metallurgical combination between diamond^brazing alloy and substrate, brazing layer having high holding force, consistent with modern green design and green manufacturing, no environment harmful, high exposure, large storage space of wear debris, high effective utilization and long using time, so they are widely used in machining, geological exploration and stone materials processing. The mechanism of high temperature brazing diamond in protective furnace with Ni-Cr alloy was investigated, and methods of brazing diamond with little thermal damage and improving the self-sharpening action of brazing layer were explored.The main contents in this paper are summarized as follows:1、Ni-Cr brazing alloy was used to brazing diamond in protective furnace, on the surface of diamond, it is flaky carbide Cr3C2and prismatic carbide Cr?C3, the growth direction of carbide Cr3C2has a certain relationship with the atom arrangement of diamond lattice plane, carbide Cr7C3nucleates and grows on the surface of Cr3C2, at the interface between diamond and brazing layer, it is gradient transition of diamond/Cr3C2/Cr7C3/brazing alloy layer. The micro structure of brazing layer is matrix y-Ni solid solution, carbide Cr7C3、Cr23C6and compound CrB uniformly distributes on the matrix. The hardness of brazing layer is about800HV0.2g, at the interface between brazing layer and steel matrix.it forms gradient transition. After brazing, a small part of diamond graphitizes. at the top of diamond, it is pressure stress, at the bottom of diamond, it is tensile stress, only a few diamonds generate crack.2、Ni-Cr brazing alloy added with Ni/C was used to braze diamond in protective furnace, on the surface of diamond, it forms flaky carbide Cr3C2, columnar thin rod and hollow carbide Cr7C3and filamentous metal-no-metal eutectic microstructure. The thermal damage of diamond reduces. The microstructure of brazing layer is matrix y-Ni solid solution, carbide and compound uniformly distributes on the matrix. At the same time, the hardness of brazing layer becomes smaller.3、Ni-Cr brazing alloy added with Ni/MoS2was used to braze diamond in protective furnace, chemical wetting forms between diamond and brazing alloy. After brazing, not only carbide Cr3C2、Cr7C3but also a few carbide Mo2C forms on the surface of diamond, with the increase of Ni/MoS2in brazing alloy, the amount of hollow carbide Cr7C3gradually decreases. The thermal damage of diamond reduces. The micro structure of brazing layer does not have a large change, carbide and compound uniformly distributes on the matrix. The hardness of brazing layer declines.