Cemented Carbide Cutting Tool Composition for Crack-Resistant Hardness
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Solution Overview
Problem
Cutting tools made of cemented carbide face challenges in wear resistance, chipping, and breakage, with a need for improved crack resistance and reduced Cobalt content while maintaining hardness for enhanced performance in metal cutting applications.
Innovation Solution
A cutting tool with a cemented carbide substrate comprising 80-96 wt% WC, 2.5-13 wt% Ni, and specific weight ratios of Fe and Co, treated with shot peening at elevated temperatures to increase crack resistance and maintain hardness, particularly on the rake face, which is critical for metal cutting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Cobalt content in cemented carbide is reduced to improve wear resistance, then hardness increases, but toughness and crack resistance deteriorate
Solution Approach 1:
The invention changes the chemical composition parameters by substituting Cobalt with Nickel and Iron, specifically using 2.5-13 wt% Ni and 0.5-5 wt% Fe to replace traditional Co-containing binders. This parameter change maintains hardness while improving crack resistance and toughness, resolving the contradiction between wear resistance and reliability
Solution Approach 2:
The invention creates a composite binder system using Ni-Fe alloy combinations instead of pure Co or traditional Co-based binders. The specific weight ratio of Fe/Ni (0.05-2) creates a synergistic composite material that provides both the hardness needed for wear resistance and the toughness required for crack resistance
2Reliability
If shot peening is applied to increase crack resistance, then surface toughness improves, but surface hardness may decrease
Solution Approach 1:
The invention changes the physical parameters of shot peening by controlling the alumina bead size (50-200 μm) and applying peening at elevated temperatures (200-600°C). These parameter changes allow the surface to develop compressive residual stresses that improve crack resistance while the high WC content (80-96 wt%) maintains surface hardness
Solution Approach 2:
The invention applies shot peening selectively to create a surface layer with different properties from the bulk material. The surface layer develops enhanced crack resistance through compressive stresses while the underlying bulk material maintains its hardness and structural integrity, achieving local quality differentiation
3Strength
If the WC content is increased to improve hardness, then wear resistance improves, but toughness and ductility worsen
Solution Approach 1:
The invention uses a composite structure with 80-96 wt% WC hard phase dispersed in a Ni-Fe metallic binder matrix. This composite architecture allows the WC particles to provide hardness and wear resistance while the continuous Ni-Fe binder phase provides toughness and ductility, resolving the contradiction between hardness and toughness
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 significantly enhances the combination of toughness and hardness, leading to improved wear resistance and prolonged tool life by increasing crack resistance without compromising plastic deformation resistance, thereby addressing the limitations of traditional cemented carbide cutting tools.
Implementation Method 1
Effects of shot peening of cemented carbide is described by Wang et al., 'Effect of shot peening on the residual stresses and microstructure of tungsten cemented carbide', Materials and Design 95, year 2016, pages 159-164. It is shown that compressive residual stresses are induced in the surface layer, both in the Co and in the WC.
Implementation Method 2
wherein P is the load [N] of a Vickers hardness indentation and a̅ is the average crack length [μm] of each crack formed at the corners of the Vickers hardness indentation
Data Source
AI summary
A cutting tool includes a substrate of cemented carbide including hard constituents in a metallic binder. The hard constituents includes WC and the WC content in the cemented carbide is 80-96 wt%. The cemented carbide has a Ni content of 2.5-13 wt%, a weight ratio of Fe / Ni < 1.5 and a weight ratio of Co / Ni < 0.825. The cutting tool includes a rake face, a flank face and a cutting edge there between, wherein the hardness H is measured with Vickers indentation and the crack resistance W is the ratio of the load to the total crack lengths of the cracks in the corners of said Vickers indentation. The product of the hardness at the rake face H(rake) and the crack resistance at the rake face W(rake) for the cutting tool is H(rake)*W(rake) > 2000 HV100*N/µm.