Cutting Element with Low Metal Concentration

Abstract

In one aspect of the present invention, a downhole fixed bladed bit comprises a working surface comprising a plurality of blades converging at a center of the working surface and diverging towards a gauge of the bit, at least on blade comprising a cutting element comprising a superhard material bonded to a cemented metal carbide substrate at a non-planer interface, the cutting element being positioned at a positive rake angle, and the superhard material comprising a substantially conical geometry with an apex comprising a curvature.

1 . A cutting element, comprising:
 a carbide substrate bonded to body of sintered polycrystalline diamond at a non-planar interface that intersects a central axis of the cutting element;   the diamond comprising a tapered side face leading to an apex along the central axis;   the apex comprises a curvature starting at a transition from side face to the curvature;   a volume defined by the apex comprises less than 5 percent metal concentration by volume; and   95 percent of interstices in the volume comprises some metal.   
     
     
         2 . The cutting element of  claim 1 , wherein the transition comprises diameter of width less than a third of a diameter of width of the carbide substrate. 
     
     
         3 . The cutting element of  claim 1 , wherein the diameter of the transition is less than a quarter of the diameter of the substrate. 
     
     
         4 . The cutting element of  claim 1 , wherein the curvature is a radius of curvature. 
     
     
         5 . The cutting element of  claim 3 , wherein the radius of curvature is less than 0.120 inches. 
     
     
         6 . The cutting element of  claim 1 , wherein the curvature is defined by a portion of an ellipse. 
     
     
         7 . The cutting element of  claim 1 , wherein the curvature is defined by a portion of a parabola 
     
     
         8 . The cutting element of  claim 1 , wherein the curvature is defined by a portion of a hyperbola. 
     
     
         9 . The cutting element of  claim 1 , wherein the curvature is a catenary. 
     
     
         10 . The cutting element of  claim 1 , wherein the curvature comprises a continuously varying radius of curvature. 
     
     
         11 . The cutting element of  claim 1 , wherein the curvature is defined by a parametric spline. 
     
     
         12 . The cutting element of  claim 1 , wherein the non-planar interface comprises an elevated flat region that is joined to a cylindrical portion of the substrate by a single tapered surface. 
     
     
         13 . The cutting element of  claim 1 , wherein the elevated flat region comprises a larger diameter of width than the diameter of the transition. 
     
     
         14 . The cutting element of  claim 1 , wherein a volume of the body of polycrystalline diamond is greater than a volume of the substrate. 
     
     
         15 . The cutting element of  claim 1 , wherein a thickness of the body of polycrystalline diamond along the central axis is greater than a thickness of the substrate along the central axis. 
     
     
         16 . The cutting element of  claim 1 , wherein the body of sintered polycrystalline diamond comprises a generally cylindrical region intermediate the side face and the interface with the carbide substrate. 
     
     
         17 . The cutting element of  claim 1 , wherein the tapered side face forms an angle of less than 45 degrees with the central axis.