Steel Tooth Drill Bit Hardfacing for Crack Resistance

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Solution Overview

Problem

Steel tooth drill bits suffer from tooth breakage due to cracking at the base of the weld deposit and carburized area under iron-based hardfacing, which propagates during service, reducing durability and performance.

Innovation Solution

Applying nickel-based hardfacing at the bases of the teeth and surrounding cone shell, combined with iron-based hardfacing on the crest and flanks of the teeth, to enhance durability and prevent crack propagation into the steel substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If iron-based hardfacing is applied to the teeth, then durability and impact resistance are improved, but thermal cracks and crack propagation occur at the base of the teeth

Engineering Contradiction:

ImprovedurabilityVSAvoidcrack resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies different hardfacing materials to different regions of the tooth structure. Iron-based hardfacing is applied to the crest and flanks where impact resistance is needed, while nickel-based hardfacing is applied to the base portions where crack resistance is critical. This local differentiation resolves the contradiction by optimizing each region for its specific functional requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses a composite hardfacing structure combining iron-based and nickel-based materials. The iron-based hardfacing provides durability and impact resistance on the tooth surfaces, while the nickel-based hardfacing provides crack resistance and thermal stress management at the base. This composite approach allows both materials to contribute their advantageous properties to the overall tooth structure.

Inventive Principle:

Principle #40Composite materials

2Reliability

If nickel-based hardfacing is applied to the bases of the teeth, then crack propagation is reduced, but impact resistance at the tooth crest may be compromised

Engineering Contradiction:

Improvecrack resistanceVSAvoidimpact resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Reliability

If thermal stresses are managed during welding, then crack propagation is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvecrack resistanceVSAvoidwelding complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs specific welding parameters and thermal management techniques during the hardfacing application process. By controlling heat input, welding speed, and cooling rates, the thermal stresses that cause cracking are minimized. This allows the use of nickel-based hardfacing at the tooth bases without significantly increasing manufacturing complexity.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This combination significantly reduces cracking and enhances the overall durability of the drill bit by managing thermal stresses and corrosion, improving its performance and longevity.

Implementation Method 1

the thermal stresses in nickel-based hardfacing are not as great as in iron-based hardfacing, such that nickel-based hardfacing is less likely to have thermal cracks

Methodology Applied

Scientific EffectThermal stress management: Thermal Expansion

Implementation Method 2

A second hardfacing formed from an iron-based material is located at and adjacent to the top portions of the teeth

Methodology Applied

Scientific EffectHardfacing: Case Hardening

Implementation Method 3

The manufacturing cracks can be caused by a variety of sources, but are primarily from the thermal stresses induced during the welding process while using iron-based hardfacing materials

Methodology Applied

Scientific EffectThermal stress: Thermal Expansion

Data Source

PatentEP2153012B1Steel tooth drill bit with improved tooth breakage resistance

Publication Date: 2012.08.15 BAKER HUGHES CO

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AI summary

A drill bit (11) having steel teeth (25) is provided with a combination of hardfacing materials (41, 43) on the teeth. The bases of the teeth are hardfaced with nickel-based materials (31) to significantly reduce any potential cracking therein. Portions of the supporting cones adjacent the teeth also may be fabricated with the nickel-based (31) hardfacing. All other portions of the teeth are hardfaced with iron-based materials (33).