Smith International, Inc.

John (Youhe) Zhang

Thomas W Oldham

Kumar T Kembaiyan

Yuelin Shen

Cutting elements include an ultra-hard body, e.g., comprising diamond, that is attached to substrate, e.g., comprising a cermet. An interface exists between the body and the substrate, and an angle of departure as measured between the interface and a free edge of the cutting element within one or both of the body and substrate, is less than about 90 degrees to provide a desired stress reduction along the interface. The angle of departure can be from about 3 to 87 degrees. The desired reduced angle of departure is provided by a surface feature disposed along an outer side surface of the cutting element adjacent a free edge of the interface. The surface feature can in the form of a groove disposed circumferentially around the body and/or substrate outer side surface, that is configured to provide the desired reduced angle of departure within the body and/or substrate.

Cutting element having stress reduced interface

Drill bit reinforcing members or blanks of this invention are formed from high-strength steels having a carbon content less than about 0.3 percent by weight, a yield strength of at least 55,000 psi, a tensile strength of at least 80,000 psi, a toughness of at least 40 CVN-L, Ft-lb, and a rate of expansion percentage change less than about 0.0025%/&#xb0; F. during austenitic to ferritic phase transformation. In one embodiment, such steel comprises in the range of from about 0.1 to 0.3 percent by weight carbon, 0.5 to 1.5 percent by weight manganese, up to about 0.8 percent by weight chromium, 0.05 to 4 percent by weight nickel, and 0.02 to 0.8 percent by weight molybdenum. In another example, such steel comprises in the range of from about 0.1 to 0.3 percent by weight carbon, 0.9 to 1.5 percent by weight manganese, 0.1 to 0.5 percent by weight silicon, and one or more microalloying element selected from the group consisting of vanadium, niobium, titanium, zirconium, aluminum and mixtures thereof.

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Tomball, TX, United States of America

John (Youhe) Zhang