Coated Cutting Tool with Eta-Phase Grains for Comb-Crack Resistance
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Solution Overview
Problem
Cutting tools for milling operations face challenges with comb crack resistance, wear resistance, and toughness, particularly in high-temperature applications like cast iron milling, due to the formation of comb cracks and rapid wear when the binder is attacked.
Innovation Solution
A cemented carbide composition with controlled Co and Cr contents, fine dispersed eta phase grains, and a PVD coating enhances comb crack resistance and wear resistance by improving chemical resistance, toughness, and hardness, with a specific carbon content adjustment during sintering to achieve evenly distributed eta phase grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the Co content in cemented carbide is increased to improve toughness, then toughness is improved, but comb crack resistance deteriorates and chemical resistance to cooling media worsens
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Co content within 6-12 wt% and Cr content within 0.1-2.5 wt%, along with adjusting carbon content to -0.10 to -0.30 wt% (substoichiometric). This optimized compositional parameter range resolves the contradiction by finding the optimal balance point where toughness is sufficient while comb crack resistance and chemical resistance are maintained.
Solution Approach 2:
The patent creates a composite cemented carbide material containing WC grains, eta phase grains, and a metallic binder with controlled Co and Cr contents. The eta phase grains (4-5 vol%) act as a reinforcement phase that improves comb crack resistance while the controlled binder composition provides toughness and chemical resistance, resolving the contradiction through composite material design.
2Reliability
If the eta phase content is increased to improve comb crack resistance, then comb crack resistance is improved, but toughness deteriorates due to Co consumption and brittleness
Solution Approach 1:
The patent controls the eta phase content within 4-5 vol% and adjusts the Co content to 6-12 wt% to prevent excessive Co consumption. This parameter control ensures that eta phase grains provide sufficient comb crack resistance without consuming so much Co that the binder becomes too brittle, thus resolving the contradiction between comb crack resistance and toughness.
Solution Approach 2:
The patent ensures even distribution of eta phase grains throughout the cemented carbide matrix, creating local quality consistency. This uniform distribution prevents localized brittleness and ensures that the eta phase provides comb crack resistance without creating weak points that would compromise overall toughness.
3Reliability
If the Cr content is increased to improve chemical resistance and strengthen the binder, then chemical resistance and strengthening are improved, but the cemented carbide becomes too hard and brittle for ISO-K milling
Solution Approach 1:
The patent controls the Cr content within 0.1-2.5 wt% and maintains the Cr/Co ratio within 1.0-2.5%. This precise parameter control allows Cr to provide sufficient chemical resistance and binder strengthening while preventing excessive hardness and brittleness that would make the material unsuitable for ISO-K milling applications.
4Strength
If the Co content is increased to improve toughness, then toughness is improved, but sensitivity to chemical attacks by cooling media and work piece material increases
Solution Approach 1:
The patent controls the Co content within 6-12 wt% and adds Cr (0.1-2.5 wt%) to form a Cr-containing metallic binder. This compositional control reduces the binder's sensitivity to chemical attacks by cooling media and work piece material while maintaining adequate toughness, resolving the contradiction between toughness and chemical 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 composition with controlled Co and Cr contents, fine dispersed eta phase grains, and a PVD coating provides enhanced comb crack resistance, wear resistance, and toughness, resulting in improved tool life and reduced wear in milling applications.
Implementation Method 1
a coating that is deposited on the cemented carbide substrate to increase the wear resistance of the cutting tool. This coating can for example be a coating deposited with Physical Vapor Deposition (PVD)
Implementation Method 2
W that is dissolved into the metallic binder from the WC grains during the sintering of the cemented carbide
Data Source
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AI summary
The present invention relates to a coated cutting tool comprising a body of cemented carbide and a wear resistant coating thereon, wherein the cemented carbide consists of WC grains and eta phase grains embedded in a metallic binder, wherein the metallic binder comprises Co and Cr, the Co content in the cemented carbide is 6-12 wt%, the eta phase content in the metallic binder is 4-5 vol% and the average grain size of the eta phase grains is 1-5 µm, and wherein the Cr/Co ratio in the cemented carbide is 1.0 - 2.5 %.