Influence of microstructure and mechanism of vacuum brazed diamond with heavy rare earth Yb-doped Ni Cr filler alloy

In this study, a method of brazing connection between diamond and American Iron and Steel Institute 1045 (AISI 1045) using heavy rare earth Yb-doped Ni Cr filler alloy was proposed. Firstly, the effects of different doping amounts of Yb on the organization and properties of Ni Cr filler alloy were investigated. The doping of Yb alters the microstructure of the Ni Cr filler alloy, promoting the transformation of coarse dendrites into fine equiaxed grains. When the doping amount of Yb was 1.0 wt%, the microhardness of the filler alloy was up to 738.63 Hv 0.2 . Secondly, the formation of rare earth compounds Ni 7 Yb 2 and NiYb 3 can effectively inhibit the chemical corrosion of diamond by the catalytic element Ni in filler alloy. The size and morphology of the carbides were changed, and the fine carbides were conducive to improving the quality of the brazed joints . Especially when the doping amount of Yb was 1.0 wt%, the reaction between the filler alloy and the diamond interface was more intense, the carbide layer was thicker about 4.26 μm. Diamond abrasive grains had the lowest degree of graphitization and the highest hydrostatic strength of 3575.7 MPa. Moreover, the surface morphology of diamond abrasive grains was intact after the friction wear test, and the removal amount of alumina ceramics by grinding was up to 42.7 mg. It is shown that the brazed diamond has excellent mechanical properties and wear resistance.