Micro-Nano DLC Piston Ring Coating to Prevent Peeling
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Solution Overview
Problem
Existing piston ring surface treatments, particularly diamond-like carbon (DLC) plating, suffer from high residual stress leading to peeling and limited friction performance, hindering performance improvement.
Innovation Solution
A piston ring with hard plating featuring an interlayer, gradient metal nitride layer, and repetitive DLC layers, combined with metal-doped DLC layers, is applied to the OD surface, while the side face receives chrome plating, enhancing binding strength and reducing stress through a micro-nano layered structure.
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 patent divides the single-layer DLC plating into multiple thin alternating layers of DLC and metal-doped DLC, creating a multi-layered structure. This segmentation reduces the thickness of each individual layer, thereby reducing residual stress within each layer while maintaining the overall protective function through the combined structure of multiple layers.
Solution Approach 2:
The patent creates a composite plating structure by combining DLC material with metal-doped DLC material in alternating layers. This composite structure leverages the high hardness and low friction of DLC while the metal-doped layers provide stress relief and enhanced adhesion, creating a synergistic effect that improves both wear resistance and binding strength.
2Force
If a single-layer DLC plating is applied to achieve low friction coefficient, then the friction performance is improved, but the plating is prone to peeling due to high residual stress
Solution Approach 1:
The single-layer DLC plating is segmented into multiple thin alternating layers of DLC and metal-doped DLC. This segmentation distributes the residual stress across multiple interfaces and reduces the stress concentration that causes peeling, while maintaining the low friction coefficient through the exposed DLC surfaces.
Solution Approach 2:
The metal-doped DLC layers act as intermediary layers between the DLC layers. These intermediary layers serve as stress buffers and adhesion promoters, reducing the residual stress in the DLC layers and improving the binding strength at the plating-substrate interface, thereby preventing peeling while maintaining low friction.
3Duration of action of stationary object
If the thickness of DLC plating is increased to enhance protection, then the wear resistance is improved, but the residual stress increases reducing binding strength
Solution Approach 1:
Instead of applying one thick DLC layer, the patent applies multiple thin alternating layers of DLC and metal-doped DLC. This segmentation allows the total thickness to be maintained or increased for better protection and longer service life, while each thin layer maintains low residual stress levels that preserve binding strength.
Solution Approach 2:
The patent uses a composite structure of DLC and metal-doped DLC layers where the metal-doped layers provide stress relief and enhanced adhesion. This composite approach enables the plating to achieve greater total thickness for improved durability and service life without compromising binding strength, as the metal-doped layers prevent stress accumulation.
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 hardness of over 1500 HV, a friction coefficient below 0.12, and prolonged service life by preventing peeling and improving wear resistance and scuffing 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
Data Source
Figure 1
AI summary
A piston ring with hard plating, and a preparation method therefor are provided. An OD surface 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 is a chrome plating on a side face of a piston ring matrix. According to the present invention, 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 the plating stress and solve the problem of plating peeling.