Silicon Nitride Wear Resistant Member Composition Control
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Solution Overview
Problem
The production of silicon nitride wear-resistant members with high reliability and low cost is challenging due to the need for precise control of manufacturing processes, which increases costs, and the dispersion in characteristics of silicon nitride sintered bodies made from inexpensive raw materials leads to insufficient performance under severe conditions.
Innovation Solution
A method involving a material powder mixture with controlled Fe and Ca content, primary and secondary sintering steps, and hot isostatic pressing to achieve a silicon nitride sintered body with high Vickers hardness, fracture toughness, and reduced porosity, ensuring uniformity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high purity silicon nitride material powder synthesized through imido thermal decomposition method is used, then mechanical strength and fracture toughness are improved, but manufacturing cost increases and workability deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters by introducing controlled amounts of Fe (10-3500 ppm) and Ca (10-1000 ppm) elements into the silicon nitride sintered body. This parameter modification allows the use of cheaper raw materials while maintaining mechanical strength through optimized composition rather than relying solely on high purity materials
Solution Approach 2:
The invention creates a composite material system by combining silicon nitride with controlled amounts of Fe and Ca elements. This composite approach leverages the beneficial effects of these elements on sintering and mechanical properties while reducing dependence on expensive high-purity raw materials, thus improving both strength and workability
2Ease of manufacture
If inexpensive silicon nitride raw material powder manufactured through direct nitriding method is used, then manufacturing cost is reduced, but Fe and Ca contents increase leading to insufficient performance under severe conditions
Solution Approach 1:
The invention transforms the harmful effect of high Fe and Ca contents into a beneficial feature by precisely controlling these element concentrations within specific ranges (Fe: 10-3500 ppm, Ca: 10-1000 ppm). This parameter optimization enables the use of inexpensive direct nitriding method raw materials while ensuring reliable performance through controlled composition
3Strength
If secondary sintering operation is conducted to increase relative density to over 98%, then strength and uniformity are improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention performs preliminary action by controlling Fe and Ca element contents in the raw materials before sintering. This pre-control of composition enables the achievement of high strength and uniformity without requiring complex secondary sintering operations, as the controlled composition facilitates adequate densification during primary sintering alone
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 method results in wear-resistant members with Vickers hardness of 1380 or more and fracture toughness of 5.5 MPa·m1/2 or more, with dispersions in hardness and toughness within ±10%, enhancing durability and reducing production defects, thus improving manufacturing yield and reliability.
Implementation Method 1
A wear resistant member mainly formed of a silicon nitride sintered body having a volume of 4000 mm³ or more, wherein dispersions in Vickers hardness and fracture toughness of an inner portion of a wear resistant member are suppressed to be within a range of ±10%
Implementation Method 2
sintering the compact body at a temperature of 1400 to 1500 °C; further sintering the compact body at a temperature of 1500 to 1650 °C in a nitrogen gas atmosphere of 10 atm or higher
Data Source
Figure 1~2B
Figure 3
AI summary
A wear resistant member formed of silicon nitride sintered body having a volume of 4000 mm3 or more, the silicon nitride sintered body containing 1 to 5 mass% of a rare earth component in terms of rare earth element, 1 to 6 mass% of an Al component in terms of Al element, 10 to 3500 ppm of an Fe component in terms of Fe element, and 10 to 1000 ppm of a Ca component in terms of Ca element, wherein a β-phase ratio of silicon nitride crystal grains is 95% or more, a maximum longer diameter of the silicon nitride crystal grains is 40 µ m or less, and each of dispersions in Vickers hardness and fracture toughness of an inner portion of the wear resistant member is within a range of ±10 %. According to this structure, the wear resistant member can be manufactured with a low cost, and there can be provided a wear resistant member comprising a silicon nitride sintered body excellent in reliability and the dispersion in characteristics is effectively suppressed.