Alpha/Beta-Sialon Cutting Tools Pressureless Sintering
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Solution Overview
Problem
Sialon ceramics used as cutting tools face challenges with wear resistance at high temperatures and require costly energy-intensive sintering processes, leading to local overheating and premature failure due to low thermal conductivity and increased oxygen content from oxidic sintering aids.
Innovation Solution
Incorporating titanium dioxide (TiO2) as a sintering additive that converts to TiN, combined with a starting material composition of α-Si3N4, AlN, and rare earth oxides, allows for pressureless sintering with enhanced compaction and reduced oxygen content, improving wear resistance and edge stability without increasing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxidic sintering aids are used to achieve sufficient compaction during sintering, then the sintering activity is improved, but the high-temperature wear resistance deteriorates due to low thermal conductivity and glass phase softening
Solution Approach 1:
The patent changes the chemical composition parameter by replacing traditional oxidic sintering aids (Y2O3, Al2O3) with titanium oxide (TiO2) in amounts of 0.1-3% by weight. This parameter change transforms the sintering mechanism while improving high-temperature properties, as TiO2 converts to TiN during sintering, providing both sintering activity and enhanced wear resistance at elevated temperatures.
Solution Approach 2:
The patent converts the typically harmful effect of oxygen from oxidic sintering aids into a beneficial outcome. By using TiO2 as the sintering aid, the oxygen present in the system contributes to forming TiO2 itself, which then converts to TiN during sintering. This eliminates the harmful low-thermal-conductivity glass phase while maintaining sintering activity, thus converting what would be a harmful oxidizing environment into a beneficial process.
2Reliability
If gas pressure sintering is used to achieve high density and good high-temperature properties, then the wear resistance is improved, but the energy consumption and production cost increase
Solution Approach 1:
The patent enables pressureless sintering by using TiO2 as a self-sintering aid that provides sufficient compaction activity without requiring external gas pressure. The TiO2 converts to TiN during sintering, creating a self-propelling sintering mechanism that achieves high density and good wear resistance through chemical transformation rather than mechanical pressure, thus eliminating the need for energy-intensive gas pressure systems.
3Use of energy by moving object
If pressureless sintering is used to reduce energy consumption, then the production cost is reduced, but the wear resistance at high temperatures deteriorates due to increased oxygen content from oxidic additives
Solution Approach 1:
The patent changes the chemical composition parameter by using TiO2 instead of traditional oxidic sintering aids in pressureless sintering. This parameter change fundamentally alters the sintering mechanism: TiO2 converts to TiN during pressureless sintering, providing both the necessary compaction force and eliminating excess oxygen. The resulting TiN phase provides excellent wear resistance at high temperatures while maintaining the energy-saving advantages of pressureless sintering.
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 achieves high-temperature wear resistance and edge stability comparable to gas-pressure sintered sialons, with increased Vickers hardness, crack toughness, and edge resistance, enabling higher cutting speeds and reduced wear, while maintaining economic production through pressureless sintering.
Implementation Method 1
When sintering under a nitrogen atmosphere, titanium dioxide essentially converts completely, i.e. at least 95%, into TiN
Implementation Method 2
α/β-Sialons with final densities greater than 99% of the theoretical final density are currently either sintered at temperatures above 1750 °C
Data Source
Figure 1
AI summary
The invention relates to α/ß-sialon-based materials. The invention particularly relates to α/ß-sialon-based materials that have an improved sintering activity and impart high edge strength to the sintered molded articles made of said materials.