Coated Cutting Tool Insert Comb Crack Resistance
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Solution Overview
Problem
Existing cemented carbide cutting tools face challenges in simultaneously improving toughness, abrasive wear resistance, adhesive wear resistance, and comb crack resistance when machining low and medium alloyed steels and stainless steels, particularly under unstable conditions.
Innovation Solution
A cemented carbide cutting tool insert with a specific composition of 12.0 to 15.0 wt% Co, 0.52 to 0.64 wt% Cr, and balance WC, coated with a 4.1 to 6.9 μm thick multi-layer TiCxNyOz coating and a blasted α-Al2O3 outer layer, optimized for milling operations with a balanced WC grain size and alloyed binder phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the binder phase content is lowered to reduce comb crack formation, then comb crack resistance is improved, but toughness properties deteriorate
Solution Approach 1:
The invention changes the chemical composition parameters of the binder phase by adding tungsten (0.5-2.0 wt%) and chromium (0.05-0.5 wt%) to cobalt, creating a modified binder that provides both comb crack resistance and toughness through altered metallurgical properties
Solution Approach 2:
The invention creates a composite binder system combining cobalt with tungsten and chromium elements, where the composite material properties provide both the required toughness and resistance to comb crack formation that neither metal alone could achieve
2Temperature
If cubic carbide content is increased to enable high cutting speed machining, then high temperature resistance is improved, but comb crack formation increases
Solution Approach 1:
The invention optimizes the cubic carbide content parameter to a specific range (0.5-2.0 wt%) that provides sufficient high-temperature stability for high-speed machining while remaining low enough to prevent excessive comb crack formation, representing a precise parameter balance
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 provides improved cutting performance across various wear types, including enhanced comb crack toughness, extending tool life and reliability in both wet and dry machining conditions.
Implementation Method 1
a coating including an innermost layer of TiCxNyOz with columnar grains and a layer of κ-Al2O3 with a top layer of TiN
Implementation Method 2
Improved abrasive wear can be obtained by increasing the coating thickness
Data Source
AI summary
The present invention discloses a coated cutting tool insert particularly useful for dry and wet machining, preferably milling, in low and medium alloyed steels, stainless steels, with or without raw surface zones under severe conditions such as vibrations, long overhang and recutting of chips. The insert is characterized by WC—Co cemented carbide with a W and Cr alloyed Co-binder phase and a coating including at least three TiCxNyOz layers and a top layer at least on the rake face of a smooth α-Al2O3.