Performance improvement of PDC and PDC bits by cryogenic treatment

Abstract

Polycrystalline diamond compact (PDC) is one of the most widely used cutting tools in the field of oil and gas drilling. In this paper, PDC was cryogenically treated at temperature of around −190 °C and then the mechanical properties such as microhardness, wear ratio, and impact toughness after cryogenic treatment were tested. The morphology, elemental composition and crystal structure of the PDC was investigated by scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD). Meanwhile, the residual stress of the PCD layer was analyzed using Raman spectroscopy. Untreated and cryogenically treated PDC were respectively fabricated into drill bits and the drilling performance were tested. The results showed that the average microhardness of the PDC after cryogenic treatment was increased by 5.3GPa/10.4%, the maximum wear ratio was increased by 11.8%, and the impact toughness was greatly improved to reach 420 J and increased by 79.4% on average. The average rate of penetration (ROP) of the bit equipped with untreated PDC was 1.03 m/h, while the ROP of the bit equipped with cryogenically treated PDC was 1.56 m/h, increased by 51.4%. Microscopic characterization revealed that the change of fracture mode and the evolution of residual stress in PDC was the main mechanism for the improvement of mechanical properties.