Si-N Piston Ring Coating for Wear and Peeling Resistance
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Solution Overview
Problem
Piston rings face increased wear and peeling due to severe usage environments characterized by high combustion temperatures, low-viscosity lubricants, and reduced oil amounts, leading to inadequate wear and peeling resistance in existing Cr—Si—N-based films.
Innovation Solution
A piston ring with a film containing Si and N, formed using a physical vapor deposition method under specific conditions of 2 to 6 Pa pressure and −5 to −18 V bias voltage, achieving a Si content of 1.1 to 7.5 at%, crystallite size of 10 to 30 nm, and compressive residual stress of 400 to 800 MPa, which enhances peeling, crack, and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a Cr—Si—N-based film is formed by ion plating method to increase hardness, then wear resistance is improved, but crack resistance and peeling resistance deteriorate
Solution Approach 1:
The invention changes the deposition parameters from ion plating to physical vapor deposition, specifically controlling pressure (0.1 to 10 Pa) and bias voltage (−5 to −50 V) to achieve optimal film properties. This parameter optimization allows the film to simultaneously achieve high hardness (1000-2000 HV) and excellent crack/peeling resistance by controlling the Si content (1-10 at%) and crystallite size (10-50 nm).
Solution Approach 2:
The invention creates a composite film structure by adding Si to CrN, forming a Cr—Si—N-based film with a mixed crystal and amorphous phase structure. This composite material approach allows the film to combine the hardness benefits of crystalline phases with the crack resistance of fine-grained and amorphous structures, achieving simultaneous improvement in all three properties: wear resistance, crack resistance, and peeling resistance.
2Power
If the usage environment becomes more severe with high combustion temperature and low-viscosity lubricant, then engine performance is improved, but wear amount of piston ring increases
Solution Approach 1:
The invention optimizes the film deposition parameters (pressure: 0.1 to 10 Pa, bias voltage: −5 to −50 V) to create a film with specific properties (hardness: 1000-2000 HV, Si content: 1-10 at%, crystallite size: 10-50 nm) that can withstand severe engine conditions including high combustion temperatures and low-viscosity lubricants, thereby maintaining low wear while preserving engine performance.
Solution Approach 2:
The invention achieves a fine crystal grain structure with crystallite size controlled at 10-50 nm, creating a densely packed microstructure that enhances the film's ability to resist wear under severe conditions. The fine-grained structure provides numerous grain boundaries that impede crack propagation and maintain film integrity under thermal and mechanical 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 solution provides a piston ring with significantly improved peeling, crack, and wear resistance, reducing the occurrence of cracks and peeling while maintaining sufficient hardness and elastic deformation for effective sliding performance.
Implementation Method 1
a step of forming a film containing Si and N in a chamber using a physical vapor deposition method so as to cover at least a part of the surface of the substrate
Data Source
AI summary
A piston ring includes a substrate, and a film covering at least a part of a surface of the substrate. The film includes Si and N. A Si content of the film is in a range of 1.1 to 7.5 at %, a crystallite size of the film is in a range of 10 to 30 nm, and a compressive residual stress of the film is 400 to 800 MPa.