Multi-Edge Working Surfaces for Polycrystalline Diamond Cutting Elements

"The present invention is a new type of PCD cutting element that has two cutting lips when in use. This new element is particularly useful for drilling in earth boring drill bits. The element has a table of superhard material bonded to a substrate of less hard material, with the superhard material containing interstices containing a catalyzing material. The element has an end working surface and a peripheral working surface, with at least part of each surface being free of catalyzing material. The element has two protruding lips, one on the end working surface and one on the peripheral working surface. The end working surface is substantially planar and the peripheral working surface is substantially perpendicular thereto. The superhard material may be polycrystalline diamond, and may incorporate regions of different abrasion resistance. The element may be exposed to the earthen formation during drilling, with the protruding lips forming on the first and second working surfaces. The invention also relates to a method of manufacturing the cutting element by forming a table of superhard material and treating at least part of each working surface to remove the catalyzing material therefrom, with the option of exposing untreated superhard material between the end and peripheral working surfaces."

A common trait of PCD elements is the use of catalyzing materials during their formation, the residue from which, often imposes a limit upon the maximum useful operating temperature of the element while in service.

The assembly is then subjected to very high temperature and pressure in a press.

Such an element may be subject to thermal degradation due to differential thermal expansion between the interstitial cobalt binder-catalyzing material and diamond matrix beginning at temperatures of about 400 degrees C. Upon sufficient expansion the diamond-to-diamond bonding may be ruptured and cracks and chips may occur.

A common problem with these PCD elements, especially when used in highly abrasive cutting application, such as in drill bits, has been the limitation imposed between wear resistance and impact strength.

In observing these PCD cutting elements in the worn condition, it was discovered that the differential wear rate caused a protruding lip to form on the wear edge of the working surface.