Plain Bearing Coating Layout to Prevent Wear and Delamination
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Solution Overview
Problem
Plain bearings made of coated titanium alloys face issues with coating wear and delamination due to insufficient lubrication, particularly in hard-to-hard PVD coating contacts and soft-to-hard coating contacts, leading to stress concentration and edge loading.
Innovation Solution
The design involves an outer ring with a softer coating on its inner surface and a harder coating on the inner ring's outer surface, with specific thickness ranges and materials like Cu-based, Tin-based, and diamond-like carbon layers, along with metal bond layers to reduce wear and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hard PVD coatings are applied on both inner ring and outer ring raceways, then wear resistance is improved, but stress concentration and coating delamination occur due to insufficient lubrication conformance
Solution Approach 1:
The patent applies different coating hardness characteristics to different locations: the outer ring raceway has a softer coating that can conform to surface irregularities, while the inner ring has a harder coating for wear resistance. This local differentiation resolves the contradiction by allowing the softer outer ring coating to reduce stress concentration and prevent delamination, while the harder inner ring coating maintains wear resistance.
2Reliability
If soft thermal sprayed coating is applied on inner ring raceway and hard PVD coating on outer ring raceway, then lubrication conformance is improved, but excessive wear occurs on the inner ring near the edge
Solution Approach 1:
The patent inverts the conventional coating arrangement by applying the softer coating on the outer ring instead of the inner ring. This inversion allows the softer material to be positioned where it can effectively conform to surfaces and distribute loads, preventing the edge loading and excessive wear that occurred when soft coating was on the inner ring.
3Weight of moving object
If titanium alloy is used for plain bearings, then weight reduction is achieved, but chemical activity and seizure risk increase during tribological sliding contacts
Solution Approach 1:
The patent uses composite material structures by applying coating layers on titanium alloy substrates. The titanium alloy provides lightweight structural properties, while the coating layers (with appropriate hardness and material composition) provide seizure resistance and controlled tribological properties, combining the advantages of both materials.
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
This configuration reduces the risk of seizure, extends the life of the plain bearing, and maintains optimal tribological properties by minimizing wear and stress concentration, thereby increasing maintenance intervals.
Implementation Method 1
the hardness of the coating on the inner surface of the outer ring is less than the hardness of the outer ring, and the hardness of the coating on the outer surface of the inner ring is greater than the hardness of the inner ring
Data Source
AI summary
A plain bearing having an outer ring and an inner ring, the outer ring and the inner ring providing respectively an inner surface and an outer surface intended to cooperate with each other for the relative movement of the outer and inner rings, the inner surface of the outer ring and the outer surface of the inner ring each including a coating including at least one layer. The hardness of the coating on the inner surface of the outer ring is less than the hardness of the outer ring, and the hardness of the coating on the outer surface of the inner ring is greater than the hardness of the inner ring.