Silicon Carbide Ceramic Sliding Parts with Dual-Size Graphite Lubricants
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Solution Overview
Problem
Conventional sintered silicon carbides exhibit poor sliding properties and are prone to seizing and cracking in a non-lubricated state due to high frictional coefficients and inadequate density, which limits their effectiveness in mechanical seals and other sliding applications.
Innovation Solution
A ceramic sintered body comprising silicon carbide with a combination of fine and coarse graphite solid lubricants, where the fine solid lubricant has a mean particle size of no greater than 5 µm and the coarse solid lubricant has a mean particle size of 10-70 µm, balanced at specific weight ratios to reduce friction and promote dense, crack-resistant structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pure sintered silicon carbide is used, then hardness and chemical resistance are improved, but sliding properties deteriorate in non-lubricated state due to high frictional coefficient
Solution Approach 1:
The patent applies composite materials by combining silicon carbide with graphite solid lubricant in specific proportions (graphite: 0.1-5.0 wt%, silicon carbide: 95.0-99.9 wt%). This composite structure maintains the hardness and chemical resistance of silicon carbide while incorporating graphite's low friction properties to improve sliding behavior in non-lubricated conditions.
2Reliability
If carbon materials are added to reduce friction, then sliding properties are improved, but density decreases leading to insufficient sealing properties and cracking
Solution Approach 1:
The patent applies parameter changes by precisely controlling the graphite content within 0.1-5.0 wt% and silicon carbide content within 95.0-99.9 wt%, along with controlling particle size distribution (graphite: 1-10 μm, silicon carbide: 3-20 μm). This optimized parameter range reduces friction while maintaining sufficient density (≥2.25 g/cm³) to prevent cracking and ensure sealing properties.
3Reliability
If graphite content is increased to reduce friction further, then sliding properties are improved, but sintering becomes difficult and density decreases
Solution Approach 1:
The patent applies parameter changes by limiting graphite content to a maximum of 5.0 wt% and controlling particle sizes (graphite: 1-10 μm, silicon carbide: 3-20 μm). This optimized parameter range ensures that graphite provides sufficient friction reduction while maintaining sinterability and achieving adequate density, avoiding the manufacturing difficulties associated with excessive graphite content.
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 ceramic sintered body achieves excellent sliding properties and minimal cracking even in a non-lubricated state, with a dense structure and improved sealing capabilities, suitable for use in mechanical seals and other sliding parts.
Implementation Method 1
a ceramic sintered body comprising silicon carbide with a combination of fine and coarse graphite solid lubricants
Implementation Method 2
balanced at specific weight ratios to reduce friction and promote dense, crack-resistant structures
Implementation Method 3
sintered silicon carbides are extremely hard and exhibit good lubricity when used with water lubrication, while their wear resistance and chemical resistance are also excellent
Implementation Method 4
a process for production of the ceramic sintered body
Data Source
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AI summary
It is an object of the invention to provide a ceramic sintered body that has a dense structure and minimal cracking and that exhibits excellent sliding properties even in a non-lubricated state, as well as a process for its production and sliding parts that employ the same. According to a preferred mode, the sintered body of the invention comprises silicon carbide as the parent material and further contains a solid lubricant A with a mean particle size of no greater than 5 µm and a solid lubricant B with a mean particle size of 10-70 µm.