Preparation of electroplated diamond core bit and its application in drilling overturned hole in the

In order to meet the requirements of high vertical precision (declination within 1%) , special drilling technique and large diameter engineering core bit are needed for drilling the overturned hole. In this paper, the large diamond engineering core bit is developed and manufactured by adopting composite electroplating method. Nickel - Cobalt alloy is used as matrix material. The bit is available in two grades of diamond MBD8 and MBD10. It contains 20% by weight 40/45 diamond ,30% by weight 45/ 50 diamond ,35% by weight 50/60 diamond and 15% by weight 60/70 diamond. The bits are electroplated at ambient temperature , current density 0.5 to 0.9 A/dm2, pH value 3-5. The optimization design of the steel body is carried out . The effect of steel body,diamond parameters and matrix on the drilling process is comprehensively analyzed. The bit is manufactured in two grades and four grit sizes to extend the range of use and increase the self - sharpness. The results show that it is reasonable of matrix prescription, technical procedure, electroplating parameters and steel body design. Its average life is 16 m and ROP is 0. 3 -0.5m.