Bi-Based Slide Member Surface Oxide Layer Seizure Resistance
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Solution Overview
Problem
Existing slide members with Bi-based overlays face challenges in achieving sufficient seizure resistance, particularly under heavy environmental loads, as Bi is brittle and requires improvements in sliding properties and fatigue resistance.
Innovation Solution
A Bi-based slide member with a surface oxide layer containing bismuth oxide, where the bismuth oxide content is controlled between 0.5 mass % and 8.0 mass % to enhance seizure resistance, and the oxide layer is confined to the surface portion to prevent fatigue degradation, with preferred orientations of the main crystal plane being (220) or (201) for improved sliding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bismuth oxide is added to the overlay to improve seizure resistance, then seizure resistance is improved, but fatigue resistance may degrade due to crack propagation from the oxide
Solution Approach 1:
The oxide layer is localized exclusively to the surface portion of the overlay, creating a functional gradient where the surface has high oxide content for seizure resistance while the bulk interior remains oxide-free to maintain fatigue resistance. This spatial differentiation of material properties resolves the contradiction between improving seizure resistance and maintaining fatigue resistance.
Solution Approach 2:
The overlay is segmented into two distinct regions: a surface portion containing the oxide layer for friction suppression, and a bulk interior portion free of oxide to prevent crack initiation. This segmentation allows each region to optimize its function without compromising the other property.
2Reliability
If excessive oxide content is present in the overlay, then seizure resistance is improved, but conformability degrades leading to overlay fatigue
Solution Approach 1:
High oxide content is confined to the surface portion where it provides seizure resistance, while the bulk interior maintains low oxide content to preserve conformability. This local quality differentiation allows the surface to be hard and friction-resistant while the bulk remains soft and conformable.
Solution Approach 2:
The oxide content parameter is changed differently in different regions: high oxide concentration (0.5-8.0 mass%) at the surface for seizure resistance, and low or zero oxide concentration in the bulk for conformability. This parameter gradient resolves the contradiction between these opposing requirements.
3Object-affected harmful factors
If Pb is replaced by Bi in the overlay to reduce environmental load, then environmental compatibility is improved, but brittleness increases requiring countermeasures
Solution Approach 1:
The overlay is designed as a composite structure combining Bi-based material with a controlled oxide layer on the surface. This composite approach maintains the environmental compatibility of Bi while the oxide layer provides enhanced mechanical properties and fracture resistance to counteract Bi's inherent brittleness.
Solution Approach 2:
The oxide layer is formed in advance on the Bi-based overlay surface to pre-enhance its mechanical properties before service. This preliminary action of oxide formation provides the Bi-based material with improved fracture resistance and surface hardness needed to overcome its brittleness.
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 controlled bismuth oxide surface layer effectively suppresses friction heat and maintains continuous seizure resistance by ensuring the oxide remains at the surface, while preventing fatigue from excessive oxide content, thereby enhancing the overall performance of the slide member.
Implementation Method 1
suppress friction heat in the early stages of use of the slide member
Implementation Method 2
oxidizing the overlay by: applying a water-soluble oil to a surface of the overlay and drying the surface of the overlay carrying the water-soluble oil, and thermally processing the overlay at a temperature ranging from 90 to 130 degrees Celsius for a duration ranging from 30 minutes to 2 hours to form a bismuth oxide in a surface portion of the overlay
Data Source
AI summary
A slide member provided with an overlay composed of a Bi-based material. A slide member includes a substrate; and an overlay including Bi or a Bi alloy provided over the substrate. A surface portion (surface-most portion) of the overlay includes an oxide layer in which a bismuth oxide, is scattered. The content of the bismuth oxide in the oxide layer represented by oxygen content is equal to or greater than 0.5% mass % and equal to or less than 8.0 mass %. The orientation intensity ratio of the main orientation plane of Bi or Bi alloy crystals in the overlay is 50% or greater. The main orientation plane of the bismuth oxide crystals in the oxide layer is the (220) plane or the (201) plane.