Piston Ring DLC Coating for Wear Resistance Without Chipping
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Solution Overview
Problem
The existing DLC film used in some engines is too thin and has high hardness, making it difficult to apply as a coating for piston rings due to insufficient adhesion and chipping issues.
Innovation Solution
A method involving the formation of a DLC film using an arc current on a carbon cathode with a density of 1.70 g/cm3 or more, in an environment with minimal hydrogen, with periodic interruptions to the arc current and decreasing arc current levels, resulting in a film with improved heat resistance and adhesion, characterized by an extinction coefficient of 0.1 to 0.4 and nanoindentation hardness of 16 to 26 GPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a DLC film with high hardness (40 to 100 GPa) is formed to improve wear resistance, then the film becomes easily chipped and has insufficient adhesion to the base material
Solution Approach 1:
The invention changes the nanoindentation hardness parameter from the conventional high range (40-100 GPa) to a specific controlled range (10-40 GPa). This parameter adjustment resolves the contradiction by reducing hardness enough to improve adhesion and reduce chipping while maintaining sufficient wear resistance through the optimized hardness level and film structure.
2Temperature
If a DLC film with thickness of 101 to 449 nm is formed to improve heat resistance, then the film is too thin for piston ring applications requiring about 5 to 20 μm thickness
Solution Approach 1:
The invention employs periodic interruption of the arc current during film formation. The arc current is supplied continuously for a predetermined period, then interrupted for a predetermined period, and this cycle is repeated. This periodic action allows controlled deposition that achieves the required thickness (5-20 μm) while maintaining heat resistance through the specific deposition pattern and film structure.
3Productivity
If arc current is supplied continuously to form a DLC film, then the film formation efficiency is high, but the film has insufficient adhesion and is easily chipped
Solution Approach 1:
The invention uses periodic interruption of arc current during film formation. The arc current is supplied continuously for a predetermined period to maintain high deposition efficiency, then interrupted for a predetermined period to allow temperature reduction and improve adhesion. This periodic action resolves the contradiction by combining efficient continuous deposition with periodic cooling that enhances film bonding to the base material.
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 method produces a DLC film with excellent heat resistance and adhesion to the base material, allowing for a thicker, more durable coating that can withstand high temperatures and reduce wear, while preventing peeling and chipping.
Implementation Method 1
a step of supplying an arc current to a cathode formed of a carbon material having a density of 1.70 g/cm3 or more, to ionize the carbon material
Implementation Method 2
a step of applying a bias voltage in an environment where hydrogen atoms are substantially absent to form a DLC film on a surface of a base material
Data Source
AI summary
A method for manufacturing a piston ring includes the following steps:(A) a step of supplying an arc current to a cathode formed of a carbon material having a density of 1.70 g/cm3 or more, to ionize the carbon material; and(B) a step of applying a bias voltage in an environment where hydrogen atoms are substantially absent to form a DLC film on a surface of a base material for a piston ring.The step (A) is continuously carried out, subsequently the step (A) is interrupted, and then the step (A) is restarted, which sequence is repeated thereby to form the DLC film having an extinction coefficient of 0.1 to 0.4 as measured using light having a wavelength of 550 nm and a nanoindentation hardness of 16 to 26 GPa.