Tungsten Carbide Composite Drill Bit Toughness

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Solution Overview

Problem

Earth-boring drill bits face challenges with brittleness and high cost due to the use of tungsten carbide, which cracks under impact and is expensive, while steel bits are prone to erosion and cutter loss.

Innovation Solution

A composite material formed from tungsten carbide crystals with a spheroidal shape and a specific grain size distribution is used to create a drill bit body, offering improved toughness, hardness, and wear resistance, combining the benefits of steel and tungsten carbide without their drawbacks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If tungsten carbide is used to provide erosion resistance, then wear resistance is improved, but brittleness increases causing cracks under impact

Engineering Contradiction:

Improvewear resistanceVSAvoidbrittleness

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention uses a composite material consisting of tungsten carbide crystals suspended in a ductile metal matrix (such as iron, nickel, or cobalt-based alloys). This composite structure combines the wear resistance of tungsten carbide with the toughness and ductility of the metal matrix, resolving the contradiction between erosion resistance and brittleness. The metal matrix provides a ductile foundation that prevents crack propagation while the dispersed carbide crystals provide hardness and wear resistance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the physical and chemical parameters of the material system by selecting specific carbide crystal size ranges (0.5 to 8 microns mean grain size) and controlling the composition of the metal matrix (6-30% carbide content). These parameter optimizations ensure that the composite achieves both high wear resistance and adequate toughness, preventing the brittleness issue associated with pure tungsten carbide.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If steel is used to provide toughness and ductility, then impact resistance is improved, but erosion resistance deteriorates

Engineering Contradiction:

Improveimpact resistanceVSAvoiderosion resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The composite structure with ductile metal matrix provides the toughness and impact resistance of steel, while the dispersed tungsten carbide crystals provide the erosion resistance. This resolves the contradiction by distributing the functional requirements to different phases of the composite material.

Inventive Principle:

Principle #40Composite materials

3Strength

If tungsten carbide hardfacing is applied to steel bits, then erosion resistance is improved, but the hardfacing cracks and peels under stress

Engineering Contradiction:

Improveerosion resistanceVSAvoidcohesion

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Instead of applying tungsten carbide as a separate hardfacing layer on steel, the invention creates an integrated composite where tungsten carbide crystals are suspended within a ductile metal matrix. This integrated structure eliminates the interface between dissimilar materials that causes cracking and peeling, while maintaining both erosion resistance and cohesion.

Inventive Principle:

Principle #40Composite materials

4Strength

If tungsten carbide matrix bits are used to provide erosion resistance, then wear resistance is improved, but cost increases significantly

Engineering Contradiction:

Improvewear resistanceVSAvoidmaterial cost

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The invention optimizes the carbide content to 6-30% by weight, which provides sufficient wear resistance while significantly reducing the amount of expensive tungsten carbide needed compared to pure carbide matrix bits. The ductile metal matrix serves as a cost-effective base material that maintains structural integrity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The tungsten carbide crystals are distributed throughout the metal matrix in specific concentrations (6-30% by weight), providing localized wear resistance where needed while maintaining overall cost efficiency. This localized distribution of expensive carbide material optimizes the balance between performance and cost.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8292985B2Materials for enhancing the durability of earth-boring bits, and methods of forming such materials

Publication Date: 2012.10.23 BAKER HUGHES CO

AI summary

An earth-boring drill bit having a bit body with a cutting component formed from a tungsten carbide composite material is disclosed. The composite material includes a binder and tungsten carbide crystals comprising sintered pellets. The composite material may be used as a hardfacing on the body and/or cutting elements, or be used to form portions or all of the body and cutting elements. The pellets may be formed with a single mode or multi-modal size distribution of the crystals.