PcBN Binder Composition With Co-W-B Phase for Tougher Cutting Tools
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Solution Overview
Problem
Existing PcBN-based compacts used for cutting tools suffer from rapid wear and tear and fracture due to insufficient fracture toughness, hardness, and thermal resistance, especially when machining hard materials, with unreacted tungsten carbide particles acting as crack propagation paths.
Innovation Solution
A polycrystalline cubic boron nitride (PcBN) composition with a ceramic binder phase comprising AlN, Al2O3, and a tough Co(x)W(y)B(z) phase, optionally including sub-stoichiometric TiN or TiCN, is manufactured by milling, drying, and high-pressure-high-temperature sintering to enhance fracture toughness and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional ceramic binder phases (TiN, TiCN, Al2O3) are used in PcBN compacts, then the hardness and thermal resistance are improved, but the fracture toughness is insufficient leading to rapid wear and fracture
Solution Approach 1:
The patent applies composite materials by combining multiple phases (cBN hard phase, AlN ceramic binder, Al2O3 ceramic binder, and Co(x)W(y)B(z) intermetallic phase) to create a PcBN composition that achieves both high hardness and improved fracture toughness. The intermetallic phase specifically addresses the fracture toughness deficiency while maintaining wear resistance.
2Ease of manufacture
If unreacted WC particles are present from milling, then the milling process is simplified, but the particles act as crack propagation paths reducing tool durability
Solution Approach 1:
The patent converts the harmful unreacted WC particles into beneficial components by having them react with Co and B during HPHT sintering to form the tough Co(x)W(y)B(z) intermetallic phase. This transforms the crack propagation sources into fracture toughness enhancers that improve tool durability.
3Stability of the object's composition
If aggressive milling of ceramic binder is performed to reach optimal target size, then the ceramic binder distribution is improved, but the physical integrity of milled constituents may be compromised
Solution Approach 1:
The patent changes the physical state and properties of constituents during HPHT sintering, where high pressure and temperature cause phase transformations and reactions that consolidate the milled constituents into a physically intact structure with improved binder distribution, recovering from any milling-induced damage.
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 composition results in robust cutting tools with improved fracture toughness and resistance to wear, effectively machining difficult-to-cut materials by uniformly dispersing mill debris and forming a tough Co(x)W(y)B(z) phase during HPHT sintering.
Implementation Method 1
the cBN powder may typically first be mixed with a ceramic binder substrate by forming a milling slurry composition of the mixed constituents with a milling liquid... This is next followed by blending the constituents in for instance either typically a ball mill, an attritor mill, or a planetary mill
Implementation Method 2
The milling slurry blend may thereafter be subjected to for example vacuum drying, air drying, freeze drying, or spray drying
Implementation Method 3
the powder blend next undergoes a high-pressure-high-temperature (HPHT) sintering consolidation operation
Implementation Method 4
Fracture toughness can be increased by converting WC mill debris into tougher phases through chemical reactions with added Co
Data Source
AI summary
Provided is a polycrystalline cubic boron nitride (PcBN) composition, which includes a cBN hard phase from about 60 vol. % to about 80 vol. % based on a total volume of the PcBN composition, and a ceramic binder phase from about 20 vol. % to about 40 vol. % based on a total volume of the PcBN composition. The ceramic binder phase includes an AlN phase, an Al2O3 phase, at least one Co(x)W(y)B(z) phase, and sub-stoichiometric (ss) titanium nitride (TiN), titanium carbonitride (TiCN), or a combination of TiN and TiCN. Associated methods of manufacturing sintered PcBN compacts, cutting tools, and compacts manufactured by using the PcBN composition are further presented.