Interface Effect and Thermodynamic Behavior between Diamond Grit and Fe–Co–Cu Pre-Alloyed Powders

This paper demonstrates a novel horizon that the Fe, Co and Cu metal elemental distribution on the diamond surface and the Gibbs free energy change of the transformation behavior in the vacuum heating-press sintering process. The reaction products on the diamond surface after sintering with Fe–Co–Cu pre-alloyed powders were examined by X-ray diffraction (XRD), Raman spectra and infrared spectrum, respectively. The distribution of every element of Fe–Co–Cu pre-alloyed powders on diamond surface were analyzed by energy dispersive X-ray spectroscopy (EDS). By thermodynamic theories the Gibbs free energy change of the transformation behavior was calculated. Results show that after sintering with Fe–Co–Cu pre-alloyed powders graphitization happens on the diamond surface and the cobalt element has enriched on the contact position. Under the vacuum heating-press sintering condition, the calculated Gibbs free energy change is negative, which demonstrates that the graphitization is a spontaneous process.