Smith International, Inc.

Naresh J Kar

Madapusi K Keshavan

Thomas W Oldham

Lance D Underwood

Cary A Roth

Brian J Armstrong

Chris Edward Cawthorne

William J Salesky

Steven J Guzowski

Steve Peterson

A rock bit for drilling subterranean formations has an improved dynamic O-ring seal for retaining lubricant around the rock bit bearings during operation of the rock bit. Such a bit has a plurality of journal pins, each having a bearing surface, and a cutter cone mounted on each journal pin and including a bearing surface. A grease reservoir is in communication with such bearing surfaces for maintaining grease adjacent to the bearing surfaces. The grease is sealed in with dynamic O-ring seals rotating against a sealing surface with a Vickers hardness of at least 1000 and vibratory burnished to have a surface finish in the range of from 5 to 32 microinches AA. Preferably, the sealing surface is formed on a seal ring interposed between the cone and journal. Preferably the sealing surface comprises a tungsten carbide composite sprayed onto the outside surface of a steel ring which is then welded to a journal.

Rock bit

A hard facing for teeth on a milled tooth rock bit comprises at least 65% by weight of a mixture of tungsten carbide particles and a balance of steel bonding the carbide particles together and to the cutter cone of the rock bit. The tungsten carbide particle mixture comprises from 35% to 80%, and preferably from 65% to 80%, by weight 20 to 30 mesh cemented tungsten carbide, and from 20% to 65%, and preferably from 20% to 35% by weight 40 to 80 mesh single crystal monotungsten carbide.

Hard facing for milled tooth rock bits

Tools, and particularly rock bit cutter cones, having 'hard' cermet cutter inserts enveloped in an intermediate layer or coating of a suitable high melting metal, and embedded in a cast steel matrix are disclosed. The cermet inserts, which usually comprise tungsten carbide in a cobalt phase (WC-Co), are coated with a layer of a metal or metal alloy, preferably nickel, which does not substantially melt during the subsequent step of casting the steel matrix of the tool. An additional layer of copper is advantageously employed on the cermet insert beneath the layer of the high melting metal, such as nickel. The coated inserts are held in appropriate position in a suitable mold and the steel matrix of the tool is poured from molten metal. The coatings on the cermet inserts prevent thermal shock to the inserts, prevent deterioration of the cermet due to diffusion of carbon into the adjacent steel, and metallurgically bonding and embedding the inserts to the steel matrix.

Cast steel rock bit cutter cones having metallurgically bonded cutter

A new and improved tungsten carbide insert for rock bits is disclosed, in which the inserts are subject to extended vibratory tumbling in order to increase their fracture toughness. More specifically the vibratory finishing or tumbling of the inserts has been increased from a typical time of 30-60 minutes to time periods of at least 90 minutes and preferably a minimum of 225 minutes. A marked improvement in toughness is obtained by this process because the size and distribution of surface flaws of the inserts were greatly reduced, and because the surface hardness of the inserts was increased, thereby resulting in an increase in the stress required to cause fracture, and a consequent increase in resistance to breakage.

Rock bit insert

A hard facing for teeth on a milled tooth rock bit comprises at least 65% by weight of a mixture of tungsten carbide particles and a balance of steel bonding the carbide particles together and to the cutter cone of the rock bit. The tungsten carbide particle mixture comprises from 35% to 80%, and preferably from 65% to 80%, by weight 20 to 30 mesh cemented tungsten carbide, and from 20% to 65%, and preferably from 20% to 35% by weight 40 to 89 mesh single crystal monotungsten carbide.

A cone blank for a rotary cone rock bit is forged, rough machined, carburized and heat-treated, followed by the formation of insert holes therein. Inserts are then pressed into the insert holes. The finished cone is subsequently sprayed with hardfacing cladding material in powdered form. The powder is thereafter densified and fused with a laser source to give a hard, erosion-resistant clad layer on the outer surface, including in the immediate vicinity of the inserts.

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Westminster, CA, United States of America

Naresh J Kar