Cutting Element Projections for Crack Arrest

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Solution Overview

Problem

Cutting elements face issues with chipping, spalling, partial fracturing, and cracking due to stress-related failures at the interface between the ultra hard material layer and the substrate, leading to early failure and reduced operating life.

Innovation Solution

The interface surface of the cutting element features a geometry with spaced apart projections that have convex upper surfaces curving continuously, balancing tensile and compressive stress regions, and an annular riser to arrest crack growth, thereby enhancing the cracking, chipping, and exfoliating characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the interface surface has spaced apart projections with flat or non-planar upper surfaces, then the cutting element can be manufactured, but cracks can grow and gain momentum leading to early failure

Engineering Contradiction:

Improvecrack resistanceVSAvoidinterface strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The upper surfaces of the spaced apart projections are formed with continuous curvature instead of flat or non-planar surfaces. This curvature causes cracks to change direction as they propagate across the interface, preventing them from gaining momentum and reducing the likelihood of catastrophic failure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Stress or pressure

If concentric annular bands are formed on the interface surface, then stress distribution is created, but cracks can grow along the entire annular surface leading to early failure

Engineering Contradiction:

Improvestress distributionVSAvoidcrack propagation resistance

Core Design Contradiction:

Stress or pressureVSReliability

Solution Approach 1:

The interface surface is segmented into multiple spaced apart projections rather than continuous annular bands. This segmentation creates discrete stress distribution zones and interrupts potential crack propagation paths, preventing cracks from growing along the entire interface surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the interface surface have different properties - the projections have convex curved surfaces that locally alter stress distribution and crack propagation behavior, while the valleys between projections provide additional crack arrest zones.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If cobalt is present in the diamond lattice structure, then the polycrystalline diamond can be formed, but thermal expansion differences cause cracking and deterioration upon heating

Engineering Contradiction:

Improvelattice structure stabilityVSAvoidheat resistance

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

Cobalt particles are removed from the interstitial spaces in the diamond lattice structure through a leaching process. This extraction eliminates the source of thermal expansion-induced cracking while preserving the diamond lattice structure, thereby improving heat resistance.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design significantly improves the durability and operating life of cutting elements by effectively arresting crack growth and reducing stress spiking, as demonstrated by improved performance in impact tests and wear resistance compared to prior art designs.

Implementation Method 1

The process of heating under high pressure is known as sintering

Methodology Applied

Scientific EffectSintering: Sintering

Implementation Method 2

inter-crystalline bonding between the diamond or CBN crystals occurs forming a polycrystalline ultra hard material diamond or CBN layer

Methodology Applied

Scientific EffectInter-crystalline bonding: Chemical Bonding

Implementation Method 3

Cobalt has a significantly different coefficient of thermal expansion as compared to diamond, and as such, upon heating of the polycrystalline diamond, the cobalt expands, causing cracking to form in the lattice structure

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

Each upper surface continuously and smoothly curves in the same direction increasing and then decreasing in height as viewed in cross-section along a plane through a diameter of the substrate

Methodology Applied

Scientific EffectStress distribution:

Data Source

PatentUS7604074B2Cutting elements and bits incorporating the same

Publication Date: 2009.10.20 SMITH INTERNATIONAL INC

AI summary

A cutting element is provided including a substrate having a periphery and an interface surface. An ultra hard material layer is formed over the substrate and interfaces with the interface surface. The interface surface also includes a plurality of spaced apart projections formed inwardly and spaced apart from the periphery and arranged around an annular path, such that each projection includes a convex upper surface defining the projection as viewed in plan view. Each upper surface continuously and smoothly curves in the same direction when viewed along a plane through a diameter of the substrate. Bits incorporating such cutting elements are also provided.