Chromium-doped Fe-Co-Ni binders for diamond cutting tools: The features of the structure, mechanical properties, and adhesion to diamond

This study is aimed at the development of novel chromium-doped Fe-Co-Ni binders for diamond cutting tools with enhanced mechanical properties, wear resistance and adhesion to diamond single crystals. Fe-Co-Ni-Cr powder mixtures were prepared by mechanical alloying to obtain uniform elemental distribution. The dependence of the mechanical properties of hot-pressed Fe-Co-Ni-Cr binders on Cr concentration has been studied. The Fe-Co-Ni-7%Cr binder fabricated by means of mechanical alloying and hot pressing is characterized by the maximal strength (3220 MPa) and hardness (114 HRB), which are due to the reduced stacking faults energy, caused by dissolution of chromium in alpha-Fe solid solution, and formation of Cr2O3 nanoparticles, which impede the dislocation gliding. The wear resistance of the Fe-Co-Ni-7%Cr binder with uniformly dissolved chromium is tenfold higher than that of the binder having the same composition but containing chromium as an individual phase. The presence of Cr in the binder leads to the improvement of its adhesion to diamond single crystals. Studies of the surface of diamond single crystals at fractures of diamond-containing segments showed that adhesion was improved due to the formation of chromium carbide (Cr3C2) sublayers.