Coated Cubic Boron Nitride Tool for Wear Resistance
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Solution Overview
Problem
Conventional coated cubic boron nitride sintered body tools experience peeling and oxidation issues due to high temperatures during high-speed cutting, leading to abnormal wear and reduced tool lifetime.
Innovation Solution
A coated cubic boron nitride sintered body tool with a coating layer comprising an upper layer of Ti, V, Zr, Nb, Mo, or Si compounds and a lower layer of alternately laminated Ti and Al compounds, providing enhanced wear resistance and heat resistance, with specific layer thicknesses and compositions to prevent peeling and thermal decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a sintered body with fine grains is used to achieve high toughness, then the strength and toughness improve, but the grain boundary area increases leading to more impurity accumulation and reduced reliability
Solution Approach 1:
The patent applies local quality by creating a dual-grain structure where the sintered body contains both fine grains (for overall toughness) and coarse grains (for clean grain boundaries). Specifically, 70-90 wt% of grains are fine (0.5-2.0 μm) while 10-30 wt% are coarse (3-6 μm), allowing the fine grains to provide toughness while the coarse grains serve as impurity sinks with clean boundaries, thus resolving the contradiction between strength and reliability.
2Strength
If the sintering temperature is increased to improve sintered body strength, then the strength increases, but the cubic boron nitride transforms to hexagonal boron nitride reducing reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sintering temperature range (1300-1700°C) and using a two-stage sintering process. The first stage at lower temperature forms the matrix, while the second stage at higher temperature (1500-1700°C) develops the coarse grain structure. This controlled parameter change achieves high strength while maintaining phase stability through optimized thermal processing.
3Productivity
If the amount of sintering aid is increased to improve sintering efficiency and strength, then the green strength and sintering efficiency improve, but the coating adhesion deteriorates due to excessive liquid phase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sintering aid content within 5-20 wt% and selecting specific compounds (borax, boron carbide, silicon carbide) with appropriate melting points. This controlled composition and amount of sintering aid provides sufficient liquid phase for grain growth and strength development while preventing excessive liquid that would harm coating adhesion, thus resolving the contradiction between sintering efficiency and coating quality.
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 extends tool lifetime by preventing abnormal wear and maintaining thermal stability at high temperatures, particularly in high-load and high-efficiency cutting operations like machining hardened steel.
Implementation Method 1
a coated cubic boron nitride sintered body tool having a coating layer comprising an upper layer excellent in wear resistance and heat resistance
Implementation Method 2
a lower layer in which first thin layer of a Ti-containing complex compound having high hardness and low Young's modulus and having an average layer thickness of 60 to 200 nm and a second thin layer of an Al-containing complex compound having low hardness and high Young's modulus and having an average layer thickness of 60 to 200 nm are laminated alternately
Data Source
AI summary
An object is to provide a coated cubic boron nitride sintered body tool which can elongate tool lifetime by restraining peeling off of a coating layer and the like due to progress of wear or oxidation. The coated cubic boron nitride sintered body tool comprises a coating layer comprising a lower layer at a substrate side and an upper layer formed thereon, the upper layer comprises a layer which comprises a compound of a compositional formula Mα (M represents one or more of Ti, V, Zr, Nb, Mo, Al, Si, α represents at least one of C, N, B and O.) and has an average layer thickness of 0.5 to 3.0 µm, and the lower layer comprises an alternately laminated material in which a first thin layer which comprises a compositional formula (Ti(1-x)Lx)β (L represents one or more of Al, B and Si, x represents an atomic ratio of L based on the sum of Ti and L, and 0.01≦x≦0.7. β represents at least one element selected from C and N.), and a second thin layer which comprises a compositional formula (Al(1-y)Jy)γ (J represents one or more of Ti, V, Cr, Zr, Nb and Mo, y represents an atomic ratio of J based on the sum of Al and J, and 0.1≦y≦0.5. γ represents at least one element selected from C and N.) are being laminated alternately, and whose average layer thickness is 0.5 to 3.0 µm.