Multilayer DLC Piston Ring Coating for Wear and Adhesion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current piston ring surface treatment methods, such as DLC coating on the outer diameter surface and gas nitriding/side surface flash chrome on the side surface, fail to provide adequate wear resistance, low friction, and durability in harsh engine environments, leading to issues like coating delamination, high roughness, and decreased sealing performance.
Innovation Solution
A wear-resistant and low-friction coated piston ring is developed, featuring a diamond-like carbon (DLC) coating on both the outer diameter and side surfaces. The coating structure includes a dual metal interlayer, a gradient DLC layer, alternating high/low hardness DLC layers, and an outer running-in DLC layer, deposited using a physical vapor deposition method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DLC coating is applied to the outer diameter surface of piston rings, then wear resistance and low friction are improved, but high-temperature resistance deteriorates due to phase transformation of diamond-like carbon
Solution Approach 1:
The patent applies composite materials by combining DLC coating with CrAlN interlayer and TiN underlayer to create a multi-layer composite coating system. The CrAlN interlayer acts as a thermal barrier and structural support, while the TiN underlayer provides strong adhesion to the substrate, enabling the DLC coating to maintain its wear-resistant properties at high temperatures without phase transformation
Solution Approach 2:
The CrAlN interlayer serves as an intermediary between the DLC coating and the piston ring substrate. It mediates the thermal and mechanical stresses, preventing direct thermal damage to the DLC layer while maintaining the low friction and wear resistance characteristics of the DLC surface
2Reliability
If DLC coating thickness is increased to improve wear resistance, then coating durability is improved, but internal stress increases leading to coating delamination
Solution Approach 1:
The patent applies local quality by creating a multi-layer structure where each layer has different properties optimized for its specific function: TiN underlayer for adhesion, CrAlN interlayer for stress management and thermal resistance, and DLC layer for wear resistance. This localized optimization allows thick coating application without delamination
Solution Approach 2:
The composite coating system distributes internal stresses across multiple layers with different mechanical properties, preventing stress concentration that would cause delamination in single-layer thick coatings
3Strength
If gas nitriding is applied to the side surface of piston rings, then surface hardening is improved, but corrosion resistance deteriorates and flexural strength decreases due to nitrogen infiltration
Solution Approach 1:
The patent replaces the gas nitriding process with a physical vapor deposition DLC coating process that achieves surface hardening without the harmful chemical infiltration effects of nitrogen, thereby maintaining both hardness and corrosion resistance
Solution Approach 2:
The DLC coating acts as an intermediary protective layer on the side surface, providing surface hardening and wear resistance while preventing corrosive environments from reaching the substrate, unlike gas nitriding which allows nitrogen infiltration
4Reliability
If side surface flash chrome thickness is increased to enhance durability, then coating durability is improved, but grain size becomes coarse leading to increased surface roughness and decreased sealing performance
Solution Approach 1:
The patent changes the deposition parameters by using physical vapor deposition with controlled sputtering conditions to produce fine-grained DLC coating structure, achieving both durability and smooth surface finish without the coarse grain structure inherent in thick flash chrome coatings
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 coated piston ring exhibits improved wear resistance, reduced friction, and enhanced heat resistance, with a smoother surface that maintains sealing performance and prevents adhesion between the piston ring and the piston ring groove.
Implementation Method 1
deposited using a physical vapor deposition method
Implementation Method 2
diamond-like carbon (DLC) coating
Data Source
AI summary
A wear-resistant and low-friction coated piston ring and a preparation method therefor are provided. The OD surface diamond-like carbon coating consists sequentially of a first metal interlayer, a second metal interlayer, a gradient DLC layer, alternating high/low hardness DLC layers, and an outer running-in DLC layer. The side surface diamond-like carbon coating consists sequentially of a metal interlayer, a gradient DLC layer, and alternating high/low hardness DLC layers. The preparation method employs physical vapor deposition to sequentially deposit composite DLC coatings on the OD surface and side surface of the piston ring. The coating is a tetrahedral amorphous carbon structure, exhibiting good thickness uniformity and fine grain structure. This improves the wear resistance of the piston ring's OD surface and side surface, reduces the aggressiveness of the piston ring side surface against the piston ring groove, and meanwhile avoids adhesion.