Sliding Surface Coating With Layered Hard Carbon for Peeling Resistance
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Solution Overview
Problem
Existing sliding members, such as piston rings, face challenges in achieving both chipping resistance and wear resistance while maintaining low frictionality and peeling resistance, with existing hard carbon layer coatings falling short in providing optimal performance under high loads.
Innovation Solution
A sliding member with a coating film comprising laminated black and white hard carbon layers, where the white hard carbon layer has a higher Vickers hardness than the black hard carbon layer, and a surface layer with a lower hardness than the white hard carbon layer, optimized for friction reduction and improved adhesion, is developed. The [sp 2/(sp 2+sp 3) ratio of the layers is tailored to enhance chipping and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hard carbon layer is provided to reduce friction, then low frictionality is improved, but peeling resistance deteriorates
Solution Approach 1:
The coating is segmented into a first hard carbon layer that provides low frictionality through its hard, lubricious surface, and a second hard carbon layer with lower hardness that provides strong adhesion and peeling resistance at the substrate interface. This segmentation resolves the contradiction between friction reduction and peeling resistance.
2Reliability
If a thick hard carbon layer is provided to improve durability, then chipping resistance and wear resistance are improved, but manufacturing complexity increases
Solution Approach 1:
Instead of forming a single thick hard carbon layer, the coating is segmented into two thinner layers with different properties. This achieves the same durability improvement while simplifying the manufacturing process, as each layer can be deposited and optimized independently with standard PVD techniques.
3Strength
If a mixed layer of hard carbon with low hardness and hard carbon with high hardness is provided to achieve both chipping resistance and wear resistance, then both properties are improved, but friction reduction and peeling resistance remain insufficient
Solution Approach 1:
The coating is clearly segmented into a first hard carbon layer optimized for wear resistance and a second hard carbon layer optimized for chipping resistance and adhesion. This clear segmentation, combined with specific thickness ratios and hardness differentials, ensures that friction reduction and peeling resistance requirements are met while maintaining improved chipping and wear resistance.
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 solution provides a sliding member with enhanced chipping resistance, wear resistance, and peeling resistance, while reducing friction, particularly effective for applications under high loads, such as piston rings, by leveraging the unique properties of the laminated hard carbon layers.
Implementation Method 1
even with a physical vapor deposition (PVD) method, makes it possible to form a thick hard carbon layer having excellent durability
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4~5
AI summary
To provide a sliding member exhibiting chipping resistance and wear resistance, having excellent peeling resistance (adhesion), and realizing a reduction in friction, and a coating film. The above-described problem is solved by a sliding member (10) comprising a coating film (1) on a sliding surface (16) on a base material (11). The coating film (1) includes, when a cross section thereof is observed by a bright-field TEM image, a laminated part (1A) configured by laminating, in a thickness direction (Y), repeating units including black hard carbon layers (B), relatively shown in black, and white hard carbon layers (W), relatively shown in white, and a surface layer part (1C) composed of a white hard carbon layer provided on the laminated part (1A). 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