CrN/CrCN Laminate Piston Ring Coating
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Solution Overview
Problem
Piston rings in automobile engines face challenges with scuffing, wear, and peeling resistance due to cracking and chipping of hard chromium nitride coatings, even with advanced laminated coatings, in severe mechanical and thermal environments.
Innovation Solution
A hard laminate coating comprising alternately laminated CrN and CrCN layers with controlled thickness and carbon concentration, optimized for high hardness, fracture toughness, and residual stress, formed by arc ion plating, providing improved scuffing, wear, and peeling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hard chromium nitride (CrN) coatings are formed by ion plating to improve scuffing resistance and wear resistance, then hardness is improved, but the coatings suffer from peeling due to cracking and chipping
Solution Approach 1:
The coating is divided into multiple thin layers (5-20 layers) alternating between CrN and CrCN compositions, each layer being 1-5 μm thick. This segmentation creates a laminated structure where individual layers can deform independently, preventing crack propagation through the entire coating thickness and reducing peeling at the substrate interface.
Solution Approach 2:
The invention uses a composite coating system combining CrN and CrCN layers with different mechanical properties. The CrN layers provide high hardness and wear resistance, while the CrCN layers with higher carbon content provide improved toughness and crack resistance. This composite structure synergistically combines the advantages of both materials.
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 CrN/CrCN laminate coating achieves enhanced hardness, fracture toughness, and balanced residual stress, effectively suppressing crack propagation and ensuring excellent scuffing, wear, and peeling resistance, suitable for extreme engine conditions.
Implementation Method 1
a CrN-type hard coating as thick as 10-60 μm formed on its outer peripheral sliding surface; the CrN-type hard coating comprising a CrN/CrCN laminate coating obtained by alternately laminating CrN layers and CrCN layers containing C dissolved in CrN
Implementation Method 2
formed by arc ion plating
Data Source
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AI summary
To provide a piston ring having a hard laminate coating having excellent scuffing resistance, wear resistance and peeling resistance, which can be used in an environment of high mechanical and thermal load in engines, the piston ring is provided on its outer peripheral sliding surface with a CrN-type hard coating as thick as 10-60 µm and comprising a CrN/CrCN laminate coating having hardness Hv of 1000 or more and residual compression stress of 1500 MPa or less, a laminate unit composed of a CrN layer and a CrCN layer being as thick as 30 nm or more; the CrN/CrCN laminate coating being formed by alternately laminating CrN layers and CrCN layers containing C dissolved in CrN by ion plating.