Microstructural Evolution of Diamond-Based Composites at High Temperature and High Pressure.

Improving the toughness of diamond composites has become an industrial demand. In this work, CoNiFe multi-element alloy was designed as binder for diamond-based composites prepared by high temperature and high pressure (HTHP). Two methods of mixing-sintering and infiltration-sintering were used to prepare diamond-based composites with different diamond contents. The phase diagrams of Co-C and CoNiFe-C at 6 GPa were calculated by Thermo-Calc. The results show that CoNiFe multi-element alloy promotes the sintering of diamond powder than element Co. The transverse rupture strength (TRS) of sintered diamond with CoNiFe (CoNiFe-75 vol% diamond) is higher than that of Co-Comp (Co-75 vol% diamond). The TRS of polycrystalline diamond (PCD) with CoNiFe alloy binder is up to 1360.3 MPa, which is 19.2% higher than Co-PCD. Compared with Co, using CoNiFe as binder results in a less metal residue in PCD, while the metal cluster area is smaller and the metal distribution is more uniform.