Polycrystalline diamond cutting elements having improved thermal resistance

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Polycrystalline diamond constructions are disclosed which have a polycrystalline diamond body and a substrate attached thereto, wherein the diamond body has a material microstructure comprising a plurality of bonded-together diamond crystals forming a polycrystalline matrix phase, and second phase formed from different types of materials or sintering aids designed to reduce or eliminate the amount of free Group VIII elements therein. The materials used to combine or react with Group VIII elements include Cr, Mn, Ti, Zr, Hf, V, Nb, Mo, W, Ta and alloys thereof. The sintering aids may comprise Pd, Fe, Co, Ni, Mn, Ti, TiO2, Si, alkali earth metals, alkaline earth metals, rare earth elements and O. Thus the sintering aids may be titanates, SiO2 or complex oxides. The use of such materials and the reduction and/or elimination of free Group VIII elements, in addition to graphitization, facilitates the sintering the construction at high pressure/high temperature conditions, e.g., greater than about 65 Kbar, to produce a construction having a high degree of thermal stability and/or thermal resistance when compared to conventional PCD materials. Polycrystalline diamond constructions of this invention are preferably configured as cutting elements that are disposed on drill bits used for drilling subterranean earthen formations.