Laminated Hard Carbon Coating for Low-Friction Sliding Members
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Solution Overview
Problem
Existing sliding members, particularly those used in high-load applications like piston rings, face challenges in achieving both chipping resistance and wear resistance while maintaining low friction and peeling resistance.
Innovation Solution
A coating film is designed with a laminated structure comprising alternating black and white hard carbon layers, where the white layers have higher hardness and a larger sp2/(sp2+sp3) ratio, and a surface layer composed of white hard carbon with lower hardness, to enhance chipping resistance, wear resistance, and peeling resistance, while reducing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard carbon layer with high hardness is provided to improve wear resistance, then wear resistance is improved, but friction increases
Solution Approach 1:
The coating film has spatially varying hardness properties. The soft carbon layers at specific positions reduce the overall friction coefficient by providing a more compliant sliding surface, while the hard carbon layers maintain wear resistance.
Data Source
AI summary
A sliding member including a coating film in a sliding surface on a base material. The coating film includes, when a cross section thereof is observed by a bright-field TEM image, a laminated part configured by laminating, in a thickness direction, repeating units including black hard carbon layers and white hard carbon layers and a surface layer part composed of a white hard carbon layer provided on the laminated part. A Vickers hardness of the black hard carbon layer is within a range of 700 to 1600 HV, a Vickers hardness of the white hard carbon layer is higher than a Vickers hardness of the black hard carbon layer adjacent thereto and within a range of 1200 to 2200 HV, and a Vickers hardness of the surface layer part is lower than the Vickers hardness of the white hard carbon layer and within a range of 800 to 1200 HV.