Multilayer-Coated cBN Particles for PCBN Tool Strength
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Solution Overview
Problem
Polycrystalline cubic boron nitride (PCBN) tools face issues with reduced strength and lifespan due to direct bonding between cBN particles and weak bonding with binders, leading to heat cracks and tool breakage during high-temperature processing of iron-based materials.
Innovation Solution
A multilayer-coated cubic boron nitride particle with a first coating layer of nitrides, borides, or boronitrides and a second coating layer of alloy-based nitrides is developed, reducing direct exposure and enhancing bonding with binders, improving fluidity and uniform dispersion, thereby increasing the strength and lifespan of PCBN sintered bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cBN particles are directly bonded together to form PCBN, then the material achieves high hardness, but the bonding force between cBN particles and binder becomes weak, leading to particle elimination and cracking
Solution Approach 1:
A coating layer comprising TiN, TiB2, AlN, Al2O3, or a mixture thereof is applied to the surface of cBN particles. This coating layer acts as an intermediary between the cBN particles and the binder, improving the bonding force while maintaining the high hardness of the underlying cBN structure.
Solution Approach 2:
The invention creates a composite structure where a ceramic coating layer (TiN, TiB2, AlN, Al2O3) is combined with the cBN particle core. This composite structure provides both the hardness of cBN and the improved bonding characteristics of the coating layer, preventing particle elimination and cracking.
2Device complexity
If cBN particles are directly bonded together, then the structure is simple, but heat cracks are formed and strength is reduced at high temperatures due to direct bonding
Solution Approach 1:
The coating layer serves as a thermal buffer and stress distributor between cBN particles at high temperatures. It prevents direct thermal contact and stress concentration that would otherwise lead to heat cracks, while maintaining structural integrity.
Solution Approach 2:
The coating layer changes the thermal and mechanical parameters at the particle interfaces, creating a gradient structure that reduces thermal stress concentration. This prevents heat crack formation while maintaining the overall simplicity of the PCBN structure.
3Ease of manufacture
If conventional cBN particles are used, then the manufacturing process is simple, but fluidity is poor and uniform dispersion is not achieved when mixed with binder
Solution Approach 1:
The coating layer acts as a surface modifier that improves the interaction between cBN particles and binder materials. It enhances wetting and dispersion characteristics, allowing for better fluidity and uniform distribution during the mixing and sintering processes.
Solution Approach 2:
The coating layer modifies the surface energy and chemical properties of cBN particles, changing their interaction parameters with the binder. This improves fluidity and dispersion uniformity without significantly complicating the manufacturing process.
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 multilayer coating structure reduces direct bonding between cBN particles, enhances bonding with binders, and improves the fluidity and uniformity of the PCBN sintered body, resulting in increased tool strength and extended lifespan during high-temperature processing.
Implementation Method 1
a multilayer-coated cubic boron nitride particle with a first coating layer of nitrides, borides, or boronitrides and a second coating layer of alloy-based nitrides is developed
Data Source
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AI summary
A cubic boron nitride particle according to an aspect of the present invention includes multiple coating layers formed on a surface thereof, so that the surface of the cBN particle is not directly exposed compared to the case of using a single coating layer. Accordingly, when a PCBN sintered body is formed, since the cBN particles are not directly bonded to each other, the jagged portion of the surface thereof may be reduced to thus improve fluidity when the cBN particles are mixed with the binder. A method of manufacturing a cubic boron nitride particle according to another aspect of the present invention includes a coating-layer treatment step performed so that the surface of the coating layer particle is smoothed and the particle shape is adjusted so as to be close to the circular shape after a first-coating-layer forming step.