cBN Sintered Material With Needle-Crystal Binder for Stable Cutting
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Solution Overview
Problem
Cubic boron nitride (cBN) cutting tools used for hardened steel exhibit unstable life and rapid wear due to high cutting resistance, often requiring operation at speeds of 150 m/min or less to prevent sudden defects and excessive wear.
Innovation Solution
A cBN sintered material comprising 20-80 vol% cBN particles and a binding phase with a first region of needle crystals, including borides with an aspect ratio of 1.5 or more, and a second region containing compounds or solid solutions with elements like nitrogen, carbon, boron, and Group 4-6 elements, which enhances the tool's life by preventing crack spread in the binding phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cBN cutting tools are used for hardened steel, then cutting capability is achieved, but tool life is unstable and wear progresses rapidly due to high cutting resistance
Solution Approach 1:
The invention uses a composite binding phase consisting of two distinct regions: a first region containing needle-like crystals (providing toughness and crack resistance) and a second region containing granular or spherical crystals (providing hardness and wear resistance). This composite structure allows the binding phase to simultaneously provide both toughness and wear resistance, resolving the contradiction between cutting capability and tool life stability.
Solution Approach 2:
The binding phase is designed with spatially differentiated properties: the first region with needle-like crystals is distributed to provide crack propagation resistance, while the second region with granular/spherical crystals provides localized hardness. This local quality differentiation allows different parts of the binding phase to perform specialized functions that collectively resolve the contradiction between productivity and reliability.
2Productivity
If cutting speed is increased to improve productivity, then cutting efficiency increases, but sudden defects occur and wear progresses rapidly
Solution Approach 1:
The needle-like crystal structure in the first region of the binding phase is designed to preemptively resist crack propagation before defects can develop into sudden failures. The aspect ratio control (1.05-2.0) optimizes this cushioning effect by creating a structure that deflects and arrests crack paths, allowing higher cutting speeds without sudden defects.
Solution Approach 2:
The dual-region composite binding phase provides both the toughness needed to prevent sudden defects (first region with needle crystals) and the wear resistance needed to prevent rapid wear (second region with granular/spherical crystals), enabling increased cutting speeds without the harmful effects of defects and wear.
Data Source
AI summary
A cubic boron nitride sintered material comprises cubic boron nitride particles and a binding phase. The binding phase includes a first region and a second region. The first region accounts for 1.0 vol % or more in the binding phase. The first region includes a plurality of needle crystals. Each of the plurality of needle crystals includes a boride. Each of the plurality of needle crystals has an aspect ratio of 1.5 or more in a cross-section image of the cubic boron nitride sintered material.