cBN Sintered Body Interface Oxygen Control for Chipping Resistance
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Solution Overview
Problem
High-cBN sintered materials used in cutting tools tend to experience sporadic chipping due to weak binding strength between cubic boron nitride grains, leading to a short tool life and increased costs.
Innovation Solution
A cubic boron nitride sintered material with a binder composition of WC, Co, and an Al compound, where oxygen is removed from the cubic boron nitride source material and an organic substance is attached to the surfaces, reducing oxygen presence at the grain interfaces to enhance binding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-cBN sintered material is used to increase hardness and cutting performance, then cutting ability is improved, but binding strength between grains becomes weak leading to sporadic chipping
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by specifying precise ratios of Ti (6-12 mass%), Al (3-8 mass%), and Ta (2-6 mass%), along with their compounds, to optimize both hardness and binding strength. This parameter optimization resolves the contradiction by finding the optimal composition range that maintains high hardness while preventing grain detachment
Solution Approach 2:
The invention uses a composite binder system combining multiple elements (Ti, Al, Ta) and their compounds (oxides, nitrides, carbides, intermetallic compounds) rather than a single binder material. This composite approach allows the binder to simultaneously provide strong adhesion to cBN grains and maintain structural integrity, resolving the contradiction between hardness and binding strength
2Productivity
If the content ratio of cubic boron nitride grains is increased to improve cutting performance, then material hardness increases, but sporadic chipping occurs due to weak binding
Solution Approach 1:
The invention optimizes the binder composition parameters to maintain adequate binder content even when cBN grain content is high (85-95 volume%). The specific compositional ranges of Ti, Al, and Ta compounds ensure that the binder phase has enhanced adhesion properties, allowing high cBN content for productivity while preventing grain fallout that would reduce tool life
Solution Approach 2:
The enhanced binder acts as an intermediary between the cBN grains, providing strong bonding that allows high grain content for cutting performance while preventing grain detachment that would cause chipping and reduce tool life. The binder mediates the stress distribution and maintains grain integrity during cutting operations
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
The approach results in a cubic boron nitride sintered material with improved binding strength between grains, leading to a longer tool life and reduced chipping, thus extending the cutting tool's lifespan.
Implementation Method 1
binding strength between the cubic boron nitride grains is weak
Implementation Method 2
binding strength between the cubic boron nitride grains
Implementation Method 3
removing oxygen of cubic boron nitride source material powder
Implementation Method 4
attaching an organic substance onto the cubic boron nitride source material powder
Implementation Method 5
obtaining the cubic boron nitride sintered material by sintering the powder mixture
Data Source
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AI summary
A cubic boron nitride sintered material includes: more than or equal to 85 volume% and less than 100 volume% of cubic boron nitride grains; and a remainder of a binder, wherein the binder includes WC, Co and an Al compound, and when a TEM-EDX is used to analyze an interface region including an interface at which the cubic boron nitride grains are adjacent to each other, oxygen exists on a whole or part of the interface, and a width D of a region in which the oxygen exists is more than or equal to 0.1 nm and less than or equal to 10 nm.