CBN Cutting Tip Joint Structure for Crater Wear Resistance
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Solution Overview
Problem
Existing tools with cubic boron nitride sintered cutting edge tips face issues of insufficient joint strength and oxidation leading to reduced crater wear resistance, resulting in shorter tool life.
Innovation Solution
A tool design featuring a cemented carbide substrate with a cubic boron nitride sintered cutting edge tip, where the cutting edge tip is brazed with an increased contact area and a curved joint surface to enhance joint strength and crater wear resistance, and the cubic boron nitride sintered body has a composition of 50-95% cubic boron nitride and 5-50% binder phase for improved thermal conductivity and fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cutting edge tip of cubic boron nitride sintered body has a small thickness, then the tool can be designed with compact dimensions, but the joint strength of the cutting edge tip to the substrate becomes insufficient
Solution Approach 1:
The patent applies preliminary action by forming a curved joint surface between the cutting edge tip and substrate before the actual brazing process. This curved surface geometry is pre-designed to maximize contact area and distribute thermal stresses during subsequent heating, thereby preventing joint failure while maintaining thin tip dimensions. The curved surface configuration is established in advance to ensure adequate joint strength without requiring increased tip thickness.
2Ease of manufacture
If conventional brazing is used to join the cutting edge tip to the substrate, then the manufacturing process is simple, but oxidation of the cubic boron nitride sintered body occurs causing decreased crater wear resistance
Solution Approach 1:
The patent implements an inert atmosphere by introducing a protective gas environment during the brazing process. This inert atmosphere prevents oxidation of the cubic boron nitride sintered body while the brazing operation proceeds. The protective atmosphere maintains the chemical stability of the CBN material, preserving its crater wear resistance despite the high-temperature brazing conditions.
3Productivity
If the cutting edge tip is made thinner to improve machining efficiency, then the tool can operate at higher speeds, but chemical reaction wear increases reducing tool life
Solution Approach 1:
The patent applies spheroidality by designing a curved joint surface between the cutting edge tip and substrate. This curved geometry improves heat dissipation from the thin cutting edge tip by providing better thermal contact with the substrate. The curved surface configuration reduces localized thermal accumulation that would otherwise accelerate chemical reaction wear, thereby extending tool life while maintaining the thin-tip high-speed machining capability.
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 design significantly improves joint strength and crater wear resistance, leading to extended tool life and reduced chemical reaction wear, while maintaining thermal conductivity and fracture resistance.
Implementation Method 1
cubic boron nitride has hardness next to diamond and excellent thermal conductivity
Implementation Method 2
The cutting edge tip is joined by brazing to a recess formed in the tip body
Data Source
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AI summary
A cutting edge tip of a cubic boron nitride sintered body has improved joint strength to a substrate of a cemented carbide. A cutting edge tip of a cubic boron nitride sintered body has improved crater wear resistance. A tool (10) of the present invention includes a substrate (12) of a cemented carbide and a cutting edge tip (14) of a cubic boron nitride sintered body joined to the substrate (12). The cutting edge tip (14) has a thickness covering an upper surface (12a) to a lower surface (12b) of the substrate (12). The cubic boron nitride sintered body contains 50 volume% or more and 95 volume% or less of cubic boron nitride and 5 volume% or more and 50 volume% or less of a binder phase. The cubic boron nitride has an average grain size of 1.0 µm or more and 6.0 µm or less.