Bismuth Overlay Layer Microstructure for Sliding Fatigue Resistance
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Solution Overview
Problem
Bismuth-based overlay layers for sliding members used in high-power engines suffer from brittleness and inferior fatigue resistance due to bismuth's characteristics, despite containing hard particles or solid lubricating particles for wear resistance and low friction properties.
Innovation Solution
A bismuth-based overlay layer with a polycrystalline matrix containing crystal particles having a Grain Orientation Spread (GOS) of 1 degree or less accounting for 85% or more, reinforced with additive particles such as hard or solid lubricating particles, improves fatigue resistance while maintaining wear resistance and low friction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bismuth is used as a base for the overlay layer matrix, then wear resistance and low friction properties are obtained, but brittleness and inferior fatigue resistance occur
Solution Approach 1:
The invention changes the crystallographic parameter (GOS value) of the bismuth matrix from a conventional state to a state where 85% or more of crystal particles have a GOS of 1 degree or less. This parameter change transforms the bismuth matrix from a brittle structure to one with superior fatigue resistance while maintaining its inherent wear resistance and low friction properties.
Data Source
Figure 1
AI summary
Provided is a bismuth-based overlay layer having high fatigue resistance even when additive particles are contained. In the present invention, the bismuth-based overlay layer for a sliding member includes a polycrystalline matrix containing crystal particles including a material containing bismuth or a bismuth alloy, and additive particles dispersed in the matrix, and the matrix includes a region in which the crystal particles having a GOS (Grain Orientation Spread) of 1 degree or less account for 85% or more of all the crystal particles.