PCD Elements And Process For Making The Same

Abstract

Catalyst in a sintered polycrystalline diamond (PCD) structure is dissolved in at least a portion of the structure by a liquid solvent metal. The structure is infused with the heated solvent and the solvent infiltrates interstitial spaces between consolidated diamond grains to contact residual catalyst from the sintering process. The dissolved catalyst passes to the bulk solvent and the solvent replaces the catalyst in the interstitial spaces.

Description

FIELD OF THE INVENTION[0001]This invention is related in general to the field of polycrystalline diamond elements, which are used in drill bits and other ground engaging products.BACKGROUND OF THE INVENTION[0002]To improve performance of cutting elements on earth boring tools, such as drill bits, one or more wear or working surfaces of the cutting elements are made from a layer of polycrystalline diamond (PCD) in the form of a polycrystalline diamond compact (PDC) that is attached to a substrate. This layer of PCD is often also called a “diamond table” or a “diamond crown.” A common substrate for the PCD layer is cemented tungsten carbide. PDC, though very hard with high abrasion or wear resistance, tends to be relatively brittle. The substrate, typically cobalt bonded tungsten carbide, while not as hard, is tougher than the PDC, and thus has higher impact resistance. The composite structure of a hard table bonded to the tough substrate is suitable for drilling and other downhole ap...

AI Technical Summary

Benefits of technology

The invention relates to a method for improving the thermal stability of sintered diamond compacts which involves replacing the residual catalyst materials with solvent metals that are more compatible with the diamond. The solvent metal can be heated to high temperatures in a vacuum or inert gas atmosphere to dissolve the catalyst. The resulting structure has improved thermal stability without causing stress or damage to the diamond matrix. The use of solvent metal can extend the operational temperature range of the diamond compacts and reduce processing costs.

Problems solved by technology

PDC, though very hard with high abrasion or wear resistance, tends to be relatively brittle.

Because of the presence of catalyst metal within the diamond matrix, sintered PCD exhibits thermal instability.

During use of the cutter, the thermal expansion of the catalyst contained in the interstitial spaces of the rigid diamond structure can initiate cracking in the structure compromising the structural integrity of the table.

The residual metal catalyst can also cause diamond crystals within the PDC to begin to graphitize, which can weaken the PCD structure.

Removal of the cobalt can reduce toughness of the PDC, thus decreasing its impact resistance.

Leaching can also result in removal of some of the cobalt near the table / substrate interface that cements or binds the table to the substrate, thus affecting the strength or integrity of the substrate and / or the interface of the substrate and diamond interface.

The acids used for leaching can be highly toxic and the leaching process can require many hours to as long as weeks to leach the cutter.

The leaching process requires careful handling of material by trained operators and complex equipment that adds to the cost of producing the cutter significantly,

Sintered diamond compacts produced by high pressure, high temperature processing generally incorporate residual catalytic materials between grains that can compromise the structural integrity of the compact under operational conditions.

Images