Polycrystalline diamond cutting elements having improved thermal resistance

Abstract

Polycrystalline diamond constructions of this invention 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 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.

Description

FIELD OF THE INVENTION[0001]This invention generally relates to cutting elements comprising one or more regions of bonded together diamond crystals and, more specifically, to cutting elements comprising bonded together diamond crystals that are specially engineered to provide an improved degree of thermal resistance during cutting and / or wearing operations when compared to cutting elements that are formed from conventional polycrystalline diamond materials, thereby providing improved service life in desired cutting and / or drilling applications.BACKGROUND OF THE INVENTION[0002]Polycrystalline diamond (PCD) materials and PCD elements formed therefrom are well known in the art. Conventional PCD is formed by combining synthetic diamond grains with a suitable solvent catalyst material to form a mixture. The mixture is subjected to processing conditions of extremely high pressure / high temperature, where the solvent catalyst material promotes desired intercrystalline diamond-to-diamond bon...

AI Technical Summary

Benefits of technology

[0022]Such polycrystalline diamond constructions of this invention display improved properties of thermal stability and / or thermal resistance when compared to conventional PCD materials, and are engineered to include a substrate material bonded thereto to facilitate attachment of the construction, e.g., when configured as a wear and / or cutting element, by conventional method such as welding or brazing and the like.

Problems solved by technology

A problem known to exist with such conventional PCD materials is that they are vulnerable to thermal degradation, when exposed to elevated temperature cutting and / or wear applications, caused by the differential that exists between the thermal expansion characteristics of the interstitial solvent metal catalyst material and the thermal expansion characteristics of the intercrystalline bonded diamond.

Such differential thermal expansion is known to occur at temperatures of about 400° C., can cause ruptures to occur in the diamond-to-diamond bonding, and eventually result in the formation of cracks and chips in the PCD structure during wear and / or cutting operations, rendering the PCD structure unsuited for further use.

Specifically, the solvent metal catalyst is known to cause an undesired catalyzed phase transformation in diamond (converting it to carbon monoxide, carbon dioxide, or graphite) with increasing temperature, thereby limiting practical use of the PCD material to about 750° C.

While this approach produces an entire diamond that is substantially free of the solvent catalyst material, is it fairly time consuming.

Additionally, a problem known to exist with this approach is that the lack of solvent metal catalyst within the diamond body precludes the subsequent attachment of a metallic substrate to the diamond body by solvent catalyst infiltration.

However, the difference in thermal expansion characteristics between the TSP body and the substrate, and the poor wettability of the TSP body due to the substantial absence of solvent metal catalyst, makes it very difficult to bond the TSP body to conventionally used substrates.

Since such TSP bodies are substantially devoid of a metallic substrate they cannot (e.g., when configured for use as a drill bit cutter) be attached to a drill bit by conventional brazing process.

The use of such TSP body in this particular application necessitates that the TSP body itself be mounted to the drill bit by mechanical or interference fit during manufacturing of the drill bit, which is labor intensive, time consuming, and does not provide a most secure method of attachment.

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