Micro-Nano DLC Piston Ring Coating to Prevent Plating Peeling
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Solution Overview
Problem
Existing piston rings with DLC plating face issues of high residual stress leading to peeling and limited friction performance due to inadequate binding strength between the plating and matrix.
Innovation Solution
A piston ring design featuring an OD surface with a sequential interlayer, gradient metal nitride layer, and DLC repetitive unit layer, including a DLC layer and metal-doped DLC layer, combined with chrome plating on the side face, to enhance binding force and reduce internal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the DLC plating is increased to improve wear resistance and friction performance, then the hardness and wear resistance are improved, but the residual stress increases leading to peeling of the plating
Solution Approach 1:
The DLC plating is divided into multiple thin repetitive unit layers (5-15 layers) instead of a single thick layer. Each unit layer has a total thickness of 1-5 μm, creating a multi-layered structure that reduces residual stress accumulation while maintaining overall wear resistance through the combined thickness of all layers (20-80 μm total).
Solution Approach 2:
Each DLC repetitive unit layer is composed of two different materials: DLC (diamond-like carbon) and metal-doped DLC. This composite structure combines the high hardness and low friction of pure DLC with the stress-relieving properties of metal-doped DLC, creating a balanced plating that achieves both wear resistance and reduced peeling risk.
2Device complexity
If a single-layer DLC plating is applied to simplify the structure, then the manufacturing process is simpler, but the binding strength is insufficient and peeling occurs
Solution Approach 1:
The plating structure is segmented into multiple repetitive unit layers, each containing two distinct material layers. This segmentation creates numerous interfaces between layers that enhance mechanical interlocking and distribute stress more evenly, significantly improving binding strength compared to a single-layer structure.
Solution Approach 2:
The use of composite materials (DLC and metal-doped DLC) in alternating layers creates a multi-material structure with enhanced adhesion. The different materials have complementary properties that improve interfacial bonding, preventing peeling while maintaining structural integrity.
3Ease of operation
If the DLC plating thickness is increased to reduce friction coefficient, then the friction performance is improved, but the residual stress causes peeling that limits further performance improvement
Solution Approach 1:
By segmenting the plating into multiple thin repetitive units, the structure maintains a low friction coefficient (achieved by the DLC surface layers) while preventing stress accumulation that would cause peeling. The segmented structure allows the plating to remain stable at thicknesses that would otherwise cause failure in single-layer designs.
Solution Approach 2:
The composite structure of DLC and metal-doped DLC allows the surface to maintain low friction properties from the DLC layers while the metal-doped DLC layers provide stress management. This enables the plating to achieve and maintain low friction coefficients without the detrimental effects of excessive residual stress.
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 design achieves a hardness of over 1500 HV, a friction coefficient below 0.12, and prolonged service life by preventing peeling, with excellent low friction and wear resistance.
Implementation Method 1
An existing preparation method for the DLC plating is usually a vapor deposition method. For example, the patent CN111133235A discloses a piston ring. An OD surface of the piston ring is a DLC layer which is formed by a physical vapor deposition (PVD) process
Implementation Method 2
the hard plating of the side face of the piston ring is a chrome plating on the side face of a piston ring matrix
Data Source
AI summary
A piston ring with a hard plating and a preparation method therefor are provided. An OD surface of the piston ring includes an interlayer, a gradient metal nitride layer and a DLC repetitive unit layer sequentially from bottom to top; one DLC unit layer in the DLC repetitive unit layer sequentially includes a DLC layer and a metal-doped DLC layer; and chrome plating of a side face of the piston ring is a chrome plating on a side face of a piston ring matrix. The repetitively circulating DLC layers and metal-doped DLC layers are a combination of a micron-thickness layer and a nanometer-thickness layer to form a micro-nano layered structure, so that the binding force between each plating is enhanced and the internal stress of the plating is reduced; and meanwhile, metal doping in the DLC layer can effectively reduce the plating stress and solve the problem of plating peeling.