Cemented Carbide Cutting Tool Thermal Crack Resistance
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Solution Overview
Problem
Conventional cutting tools face challenges with thermal crack resistance and wear resistance, especially during high-speed cutting or machining of difficult-to-cut materials, due to inadequate thermal diffusivity and high-temperature hardness, leading to tool chipping and reduced lifespan.
Innovation Solution
A cemented carbide with a binder phase of Co and Ni, containing WC grains with specific size and shape, and additional elements like Cr, Ta, and Nb, which enhances thermal diffusivity and toughness, combined with a coated film of DLC or diamond for improved wear resistance and thermal insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elements such as Ti, Nb, Ta, or Zr are introduced into cemented carbide to improve high-temperature hardness, then wear resistance is improved, but thermal diffusivity decreases
Solution Approach 1:
The invention changes the chemical composition parameters by introducing specific elements (Ti, Nb, Ta, Zr) at controlled concentrations (0.1-5.0 mass% each) to achieve the desired balance between high-temperature hardness and thermal diffusivity. This parameter optimization allows the cemented carbide to maintain wear resistance while improving thermal crack resistance.
2Reliability
If a coated film is provided on the surface of the tool to reduce thermal shock, then thermal crack resistance is improved, but the coated film is prone to come off at high temperatures
Solution Approach 1:
The invention creates a composite structure by combining the cemented carbide base material with a specifically designed coated film. The coated film comprises multiple layers including a bonding layer and a protective layer, creating a composite material system that simultaneously provides thermal shock resistance and maintains strong adhesion at high temperatures through the graded structure and intermediate bonding layers.
3Strength
If cutting fluid is used to decrease tool temperature, then wear resistance is improved, but thermal shock causes thermal cracks in intermittent cutting
Solution Approach 1:
The invention applies beforehand cushioning by introducing elements with high thermal conductivity (Ta, Nb, Zr) into the cemented carbide base material before cutting operations. These elements pre-establish a thermal management system within the material structure itself, creating an internal heat dissipation network that cushions against thermal shock from cutting fluid in intermittent cutting, thereby preventing thermal cracks while maintaining wear resistance.
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 cemented carbide achieves high thermal diffusivity across the tool, suppressing thermal cracks and wear, and maintaining strength and hardness, thus extending tool life and performance in demanding cutting conditions.
Implementation Method 1
heat is less likely to be transferred from the coated film on the surface of the tool to the base material inside the tool... heat is likely to be kept in the tool... The cemented carbide has high thermal diffusivity... suppressing thermal cracks
Implementation Method 2
Ceramics constituting the coated film generally has a low thermal diffusivity. Hence, when the coated film is provided on the surface of the tool, heat is less likely to be transferred from the coated film on the surface of the tool to the base material inside the tool. This provides an effect of reducing thermal shock imposed on the base material.
Implementation Method 3
the cutting tool needs to be formed of a material (base material) capable of maintaining sufficient hardness and strength even when it has a high temperature... improve the wear resistance of the cutting tool when it has a high temperature
Data Source
AI summary
There are provided a cemented carbide high in thermal diffusivity and excellent in wear resistance, and a cutting tool including a base material formed of this cemented carbide. The cemented carbide is a WC based cemented carbide in which a hard phase mainly constituted of WC grains is bound by a binder phase mainly constituted of Co, and is used for a cutting tool. The binder phase is substantially constituted of Co, or Co and Ni. A total content of Co and Ni is not less than 4.5 mass % and not more than 15 mass %. In this cemented carbide, the WC grains have an average diameter of not less than 0.4 μm and not more than 4 μm.