Rolling Bearing Coatings to Prevent Ag Transfer Adhesion
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Solution Overview
Problem
Rolling bearings used in high-vacuum, high-temperature environments face challenges with Ag coating films, as they tend to transfer and adhere to counter materials, leading to noise, vibration, and reduced lifetime, despite attempts to use environmentally friendly alternatives like Ni and W.
Innovation Solution
The use of a Cr coating film, either alone or in combination with Ag, on the surfaces of rolling elements and raceways, along with an underlayer of Ni and Cu, to prevent Ag transfer adhesion, while maintaining lubricity and conductivity, is proposed. The Cr coating film is preferably formed using sputtering or plating methods to ensure uniformity and appropriate thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ag coating film is used for lubrication, then lubricity and conductivity are improved, but Ag transfer adhesion to counter material occurs causing noise and vibration
Solution Approach 1:
A Cr coating film is introduced as an intermediary layer between the Ag coating film and the counter material (inner ring or outer ring). This intermediate Cr layer prevents direct contact and transfer adhesion of Ag to the counter material, while still allowing the Ag layer to provide lubrication. The Cr coating acts as a barrier that mediates the interaction between Ag and the counter material.
Solution Approach 2:
The invention uses a composite coating structure consisting of multiple layers: an Ag coating film for lubrication and conductivity, a Cr coating film as an intermediate layer to prevent transfer adhesion, and optionally an underlayer of Ni and Cu. This composite structure combines the beneficial properties of different materials while mitigating their individual drawbacks.
2Adaptability or versatility
If Ag is used as solid lubrication material, then environmentally-friendly alternative to Pb is achieved, but Ag is harder than Pb causing noise and vibration even with small transfer
Solution Approach 1:
The Cr coating film serves as a mediator that prevents Ag from transferring to the counter material. By blocking the direct contact between Ag and the counter material surface, the Cr layer eliminates the source of noise and vibration caused by Ag transfer, while allowing the Ag layer to maintain its environmental compatibility advantage over Pb.
3Stability of the object's composition
If Ni or W coating is used as counter material to prevent Ag transfer, then low solubility with Ag is achieved, but transfer adhesion cannot be sufficiently prevented under vacuum conditions
Solution Approach 1:
Instead of relying on a single counter material layer (Ni or W), the invention uses a composite coating structure with multiple layers including Cr as the primary barrier layer against Ag transfer. This multi-layer composite approach provides superior transfer adhesion prevention compared to single-layer solutions, especially under vacuum conditions where Ag has high tendency to transfer.
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 effectively suppresses Ag transfer adhesion, improving acoustic characteristics and prolonging the lifetime of the rolling bearing by maintaining initial smooth surfaces and reducing vibration, as demonstrated in high-temperature rotary tests under vacuum conditions.
Implementation Method 1
it is known that when Ag is used, Ag is attached (transferred to adhere) to a counter material not a little... since Ag is harder than Pb, noise and vibration may be caused even though small solid metal blanks is transferred... W and Ta as the coating film... mutual solubilities of various metal materials... W and Ni as materials of which solubility with Ag is low
Implementation Method 2
The Cr coating film is preferably formed using sputtering or plating methods to ensure uniformity and appropriate thickness
Data Source
Figure 1~2
Figure 3
AI summary
This rolling bearing is configured such that: every one of an inner ring, an outer ring and a rolling body is formed from a steel material; and (A) an Ag coating film is formed on the surface of the rolling body and a Cr coating film is formed on the raceway surface of at least one of the inner ring and the outer ring, or (B) a Cr coating film is formed on the surface of the rolling body and a Cr coating film is formed on the raceway surface of at least one of the inner ring and the outer ring.