Study On The Performance Of Diamond - Bearing Compound Drilling

This paper discusses the research process of two kinds of diamond oil drilling cutter in detail. Laboratory evaluation has been conducted for some special properties of extensive used polycrystalline diamond compact (PDC), in order to obtain breaking behavior and damage reasons of such oil drilling cutter in the process of drilling rock.(1)This study does not only involve the thermal stability test which is currently concerned in drilling engineering, but also the performance improvement of cobalt leached PDC cutters. This study has a great significance to establish an effective inspection method of PDC drilling cutter and develop new type of diamond contained composite oil drilling cutter.(2)In order to solve PDC cutters’ adaptability of penetrating different formations, preparation technology and performance test research of sintering diamond impregnated oil drilling cutter has also been conducted. The process of study contains the performance test and optimal selection of large-sized mono-crystal diamond particles, matrix alloy’s formula selection and molding experiments of diamond impregnated oil drilling cutters, overall manufacturing technology research of diamond impregnated oil drilling cutters, etc.The main research conclusions in this paper are as follows:(1) The cobalt leached method of fast wash+slow wash pickling can effectively remove the cobalt binder phase of PDC cutters by XRD results. There is no evidence of cobalt in XRD spectrum after cobalt leaching process. The cobalt leaching rate is above90%, and the leached depth by400μm in XRF spectrum.(2) The existence of metal binder cobalt has great impact on its abrasive resistance and residual stress for PDC cutters. Abrasive resistance of cobalt leached PDC cutter has been greatly improved in the same conditions. Raman characteristic peak of original PDC cutters is consistent in residual stress test, but the Raman spectrum of metal cobalt has widened, strengthened and moved up, which is less clear and weaker than cobalt leached PDC cutter. The performance of original polycrystalline diamond has been changed. Residual stress after heat treatment is0.3337GPa, which is greater than normal one0.2967GPa.(3) Make a comparison between original YK-9mono-crystal diamond and CVLT processed and metalized diamond by thermal stability test and single grain compact strength test, and finally choose metalized diamond as the material of sintering diamond impregnated cutter.(4) Select WC-25Co powder as matrix alloy, pre-alloyed it by ball-milling process with granularity distribution range in1～5μm, which accelerate sintering densification. Choose NBR+acetone granulation agent, and1470℃once hot-pressing sintering technology to have high quality sintered samples comparing the once and twice forming technology.(5) Diamond and matrix alloy are strongly combined with each other from the macro-morphology of sintered diamond impregnated cutters with intact diamond grain shape, high sintering density, and no diamond graphitization phenomena. Small-sized matrix alloy and mono-crystal diamond have obviously infiltrated with metallurgical bonding from micro-morphology of sintered diamond impregnated cutters. Sintered diamond impregnated cutters’ maximum load of the compact strength is not different and even higher than the highest drilling pressure. Abrasive-resisting experiment shows that the sintered diamond impregnated cutters are abrasive-resisting with abrasion ratio at106. In the continuous abrasive-resisting experiments, the diamond with good exposure degree does not fall off or break down by different thermal expansion coefficient. Diamond and matrix alloy are effectively bonded and infiltrated.