Gradient DLC Coating for Piston Rings With Peeling Resistance
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Solution Overview
Problem
Existing sliding members with DLC coatings face challenges in combining high wear resistance with low friction and peeling resistance, often experiencing discontinuous indentation hardness at the boundary between layers, leading to peeling issues and reduced workability.
Innovation Solution
A DLC coating with a gradual reduction in indentation hardness from the base member to the surface, featuring a two-stage indentation hardness distribution, ensures continuous hardness change and improved peeling resistance while maintaining high wear resistance and low friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the DLC coating has a constant high indentation hardness (20-70 GPa) throughout the thickness, then wear resistance is improved, but the workability and peeling resistance deteriorate
Solution Approach 1:
The patent applies local quality by creating different indentation hardness zones within the DLC coating. The coating has a first region with high indentation hardness (20-70 GPa) for wear resistance and a second region with lower indentation hardness (5-20 GPa) for workability and peeling resistance. This spatial variation in material properties resolves the contradiction between wear resistance and workability.
2Ease of manufacture
If the upper layer coating is made softer than the lower layer coating to improve workability, then workability is improved, but discontinuous indentation hardness at the boundary causes peeling
Solution Approach 1:
The patent applies parameter changes by controlling the indentation hardness distribution through specific deposition conditions. The indentation hardness gradually transitions from the high-hardness lower layer to the lower-hardness upper layer, creating a continuous gradient that prevents peeling while maintaining workability. The key parameter controlled is the indentation hardness profile, which changes continuously rather than abruptly.
3Ease of manufacture
If a two-layer DLC coating structure is used with different hardness levels, then workability is improved, but the boundary discontinuity causes peeling
Solution Approach 1:
The patent applies dynamics by creating a dynamic, continuous gradient in indentation hardness rather than a static, abrupt boundary between layers. The indentation hardness transitions smoothly from the lower layer to the upper layer, eliminating the sharp discontinuity that causes peeling. This dynamic gradient structure maintains both workability and coating integrity.
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 achieves a sliding member with enhanced wear resistance, low friction, and excellent peeling resistance, facilitating easier industrial production and application in piston rings.
Implementation Method 1
a DLC coating formed on the base member by ion plating
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Provided is a sliding member having a hard carbon coating that makes high wear resistance compatible with a low coefficient of friction and that has excellent peeling resistance. A sliding member (100) includes a base member (10) and a hard carbon coating (12) formed on the base member (10). The indentation hardness of the hard carbon coating (12) decreases gradually from the base member side to the surface side. The hard carbon coating (12) has an indentation hardness distribution at 0 ≤ T/Ttotal ≤ 0.6 approximated by a first line and an indentation hardness distribution at 0.9 ≤ T/Ttotal ≤ 1 approximated by a second line, and the intersection between the first line and the second line (T2/Ttotal, H2) satisfies Expression (1), (H3 - H1) × T2/Ttotal + H1 < H2 ≤ 0.9 × H1, and Expression (2), 0.6 ≤ T2/Ttotal ≤ 0.9.