Silicon Nitride Cutting Insert With Oxygen-Gradient Surface

Solution Overview

Problem

Sintered silicon nitride cutting inserts face challenges with thermal conductivity and densification due to high oxygen content near the surface, leading to reduced heat resistance and wear resistance, and the presence of undensified 'white portions' if oxygen levels are too low.

Innovation Solution

A sintered silicon nitride insert with a surface region having an oxygen content less than 0.8% by mass, incorporating ReMgSi2O5N, which enhances thermal conductivity and prevents undensified areas, combined with a coating layer for improved wear resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the amount of sintering aid is increased to improve densification, then denseness is improved, but thermal conductivity is lowered

Engineering Contradiction:

ImprovedensenessVSAvoidthermal conductivity

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The patent applies local quality by creating distinct regions within the sintered silicon nitride insert: a surface region (0-0.5mm depth) with low oxygen content (<0.8%) for high thermal conductivity, and an inner region with higher oxygen content (1.0-2.0%) for good denseness. This spatial differentiation allows each region to optimize its properties independently, resolving the contradiction between thermal conductivity and denseness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the oxygen content parameter as a function of depth from the surface. By controlling oxygen concentration to decrease from the inner region to the surface region, the material achieves high thermal conductivity at the surface while maintaining denseness in the interior. This parameter gradient approach allows simultaneous optimization of both contradictory properties.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the oxygen content on the surface is reduced to improve thermal conductivity, then thermal conductivity is improved, but undensified white portions remain on the surface

Engineering Contradiction:

Improvethermal conductivityVSAvoidsurface denseness

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating distinct regions within the sintered silicon nitride insert: a surface region (0-0.5mm depth) with low oxygen content (<0.8%) for high thermal conductivity, and an inner region with higher oxygen content (1.0-2.0%) for good denseness. This spatial differentiation allows each region to optimize its properties independently, resolving the contradiction between thermal conductivity and denseness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite structure within the sintered silicon nitride by combining regions with different oxygen contents and phases. The surface region contains ReMgSi2O5N phase with low oxygen for thermal conductivity, while the inner region has higher oxygen content for denseness. This internal composite structure allows the material to exhibit both high thermal conductivity and complete densification without white portions.

Inventive Principle:

Principle #40Composite materials

3Productivity

If the insert is used for high-speed machining, then productivity is improved, but excessive heating occurs reducing lifespan

Engineering Contradiction:

Improvemachining speedVSAvoidheat resistance

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent applies local quality by creating distinct regions within the sintered silicon nitride insert: a surface region (0-0.5mm depth) with low oxygen content (<0.8%) for high thermal conductivity, and an inner region with higher oxygen content (1.0-2.0%) for good denseness. This spatial differentiation allows each region to optimize its properties independently, resolving the contradiction between thermal conductivity and denseness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the harmful effect of high-speed machining (excessive heat generation) into a beneficial outcome by designing a surface region with optimized low oxygen content that provides high thermal conductivity. This allows the insert to efficiently dissipate the heat generated during high-speed machining, transforming the thermal challenge into an opportunity to demonstrate the material's superior heat dissipation capabilities and extend insert lifespan.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 insert achieves high thermal conductivity and extended lifespan by efficiently dissipating heat and preventing excessive heating during high-speed machining, while maintaining high wear resistance and avoiding surface color unevenness.

Implementation Method 1

the first region includes ReMgSi2O5N (Re is at least one of Yb and Y)... achieves high thermal conductivity and extended lifespan by efficiently dissipating heat

Methodology Applied

Scientific EffectThermal conductivity: Conduction (thermal)

Data Source

PatentUS11865624B2Insert and cutting tool

Publication Date: 2024.01.09 KYOCERA CORP

AI summary

An insert may include a sintered silicon nitride including β-Si3N4 as a main component. The area up to 0.5 mm deep from a surface of the sintered silicon nitride is a first region. The first region may include an oxygen content of less than 0.8% by mass. The first region may include ReMgSi2O5N (Re is at least one of Yb and Y). A cutting tool may include a holder that extends from a first end toward a second end and includes a pocket on a side of the first end, and the insert located at the pocket.