Low pressure bonding of PCD bodies and method for drill bits and the like

An earth boring bit, comprising

• a matrix bit body,
• a matrix carrier metallurgically bonded to said matrix bit body,
• at least one polycrystalline diamond element which is temperature stable to at least about 1,200.degree. C.,
• a tungsten coating at least 5 microns thick coated on said diamond element between said diamond element and said matrix carrier, said tungsten coating including a tungsten carbide layer adjacent said diamond element and an outer portion comprising substantially tungsten metal adjacent said matrix carrier,
• said diamond element being chemically bonded to said tungsten coating by means of said carbide layer, and said outer portion of said tungsten coating being chemically bonded to said matrix carrier, said carbide layer bonding said diamond element to said matrix carrier with a bond strength in shear of at least 5,000 pounds per square inch.

An earth boring bit, comprising:

• a matrix support,
• at least one cutter element bonded to said matrix support, said cutter element comprising at least one preformed polycrystalline diamond element which is temperature stable to about 1200.degree. C. coated with a carbide forming metal layer at least 5 microns thick,
• said metal layer being selected from the group consisting of tungsten, tantalum, and molybdenum,
• said metal layer including a carbide layer adjacent to said diamond element and a substantially metallic outer portion adjacent to said matrix support,
• said diamond element being chemically bonded to said metal layer via said carbide layer, and said outer portion of said metal layer being chemically bonded to said matrix support, said carbide layer being of sufficient thickness to bond said diamond element to said matrix support with a bond strength in shear of at least 5,000 pounds per square inch.

An earth boring bit, comprising:

• a matrix support,
• a plurality of polycrystalline diamond elements which are temperature stable to about 1200.degree., each of said diamond element being preformed into a predetermined geometrical shape and each of which includes at least one surface metallurgically bonded to said matrix support,
• a metal layer coating at least said metallurgically bonded surface of each of said polycrystalline diamond elements, said metal layer being selected from the group consisting of tungsten, tantalum, and molybdenum,
• said metal layer being at least 5 microns thick and comprising a carbide layer adjacent to and chemically bonded each of said polycrystalline diamond elements to its metal layer, said metal layer further comprising a substantially metallic outer portion metallurgically bonding said metal layer to said matrix support, said carbide layer being of sufficient thickness to bond each of said polycrystalline diamond elements of said matrix support with a bond strength in shear of at least 5,000 pounds per square inch.