cBN Sintered Body Binder Composition for Heat Crack Resistance
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Solution Overview
Problem
High-cBN sintered materials experience sudden breakage due to weak bonding forces between cubic boron nitride grains, leading to shortened tool life and increased costs in cutting operations.
Innovation Solution
Incorporating a metal compound powder with a thermal expansion coefficient close to that of cBN, dispersed with a binder, and controlling grain size to suppress heat cracks at the cutting edge, thereby enhancing the stability and durability of the cutting tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high content ratio of cubic boron nitride grains is used to increase hardness and cutting performance, then the cutting ability is improved, but the bonding force between grains becomes weak causing sudden breakage
Solution Approach 1:
The invention uses a composite binder system consisting of two distinct binder materials with different functions: a first binder that provides strong bonding between cBN grains, and a second binder that suppresses heat crack propagation. This composite approach allows the material to achieve both high cutting ability and improved reliability by distributing different functional requirements to different binder components.
Solution Approach 2:
The invention changes the chemical composition parameters of the binder system by specifying particular compounds (e.g., WC-Co for the first binder, TiAlN or TaAlN for the second binder) and their weight ratios. By adjusting these compositional parameters, the material achieves optimal balance between bonding strength and heat crack resistance, thereby improving reliability while maintaining high cBN content for cutting performance.
2Reliability
If the binder content is increased to improve bonding force between grains, then resistance to sudden breakage is improved, but the content ratio of cubic boron nitride grains decreases reducing cutting performance
Solution Approach 1:
The invention divides the binder function into two specialized components: a first binder optimized for maximum bonding strength between cBN grains, and a second binder optimized for heat crack suppression. This functional division allows each binder to be optimized for its specific purpose, achieving reliable bonding without requiring excessive total binder content that would dilute the cBN cutting phase.
Solution Approach 2:
The invention assigns different local functions to different binder components: the first binder operates primarily at grain boundaries to provide strong adhesion, while the second binder distributes throughout the matrix to suppress heat crack propagation. This localized functional assignment allows the system to achieve both bonding strength and heat resistance with minimal total binder content, preserving high cBN content for cutting performance.
3Stability of the object's composition
If metal compound powder with matching thermal expansion coefficient is added to suppress heat cracks, then stability at cutting edge is improved, but the complexity of binder composition increases
Solution Approach 1:
The invention incorporates metal compound powder (TiAlN or TaAlN) as a second binder component that specifically addresses heat crack suppression through its thermal expansion properties. While this adds a compositional element, the compound serves multiple functions: thermal expansion matching, heat crack suppression, and potential reinforcement. The structured approach of defining specific compounds and ratios manages the complexity while achieving the stability benefit.
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 solution results in a longer tool life and improved resistance to breakage and wear, ensuring enhanced performance and cost-effectiveness in cutting tools.
Implementation Method 1
incorporating a metal compound powder with a thermal expansion coefficient close to that of cBN, dispersed with a binder, and controlling grain size to suppress heat cracks at the cutting edge
Data Source
AI summary
A cubic boron nitride sintered material includes 70 vol% or more and less than 100 vol% of cubic boron nitride and a binder. The binder includes a first material and a second material. The first material is one or two or more first chemical species each including at least one first metallic element selected from the group consisting of tungsten, cobalt, and aluminum. Each of the first chemical species is a metal, an alloy, an intermetallic compound, a compound, or a solid solution. The second material is one or two or more second chemical species each including at least one second metallic element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, and chromium. Each of the second chemical species is a solid solution derived from at least one selected from the group consisting of nitride, carbide, and carbonitride. In each of the second chemical species, 0.1 atom% to 10 atom% of aluminum is dissolved in a solid state, and the second material is grains having an average grain size of 1 µm or less.