Laminated Hard Carbon Coating for Thick PVD Wear Surfaces
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Solution Overview
Problem
Existing methods for forming hard carbon films using CVD struggle to balance chipping resistance and wear resistance, and also fall short in improving low friction properties and peeling resistance, while PVD methods face challenges in forming thick, durable films with sufficient durability due to excessive compressive residual stress.
Innovation Solution
A method using an arc PVD apparatus where the substrate temperature is controlled above 200°C to form thick hard carbon films, with alternating layers of low-temperature and high-temperature deposited hard carbon layers to achieve a balanced sp2/sp3 ratio, resulting in a coating film with improved chipping resistance, wear resistance, and low friction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If CVD method is used to form hard carbon film, then chipping resistance is improved, but wear resistance deteriorates
Solution Approach 1:
The coating film is divided into multiple alternating layers with different carbon structures. Low-temperature deposited layers (sp2-rich, graphite-like) provide chipping resistance, while high-temperature deposited layers (sp3-rich, diamond-like) provide wear resistance. This segmentation allows each layer to specialize in one function, resolving the trade-off between chipping and wear resistance.
Solution Approach 2:
The invention creates a composite structure combining two types of hard carbon layers with different properties. The sp2-rich layers and sp3-rich layers are alternately stacked to form a composite coating that integrates the advantages of both carbon structures, achieving simultaneous improvement in chipping resistance and wear resistance.
2Reliability
If PVD method is used to form thick hard carbon film, then wear resistance is improved, but chipping resistance deteriorates due to excessive compressive residual stress
Solution Approach 1:
The thick coating is segmented into alternating soft and hard layers. The sp2-rich layers act as stress-relief zones that accommodate compressive residual stress, preventing film destruction. The sp3-rich layers maintain high hardness and wear resistance. This segmentation allows the thick film to be formed without excessive stress accumulation.
Solution Approach 2:
Different regions of the coating have different mechanical properties. The sp2-rich layers have lower hardness and higher ductility, providing local stress accommodation. The sp3-rich layers have high hardness and wear resistance. This local quality differentiation allows the coating to handle both stress and wear demands.
3Stability of the object's composition
If low-temperature deposition is used, then sp3 content is improved, but surface roughness deteriorates
Solution Approach 1:
The coating is segmented into alternating layers with different deposition temperatures and carbon structures. The sp3-rich layers provide hardness and composition stability, while the sp2-rich layers provide smooth surface morphology. This segmentation allows each layer to optimize for its specific function without compromising the other.
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 approach successfully forms thick hard carbon films with balanced chipping and wear resistance, and enhanced low friction and peeling resistance, suitable for sliding members, by alternately laminating layers with different sp2/sp3 ratios, effectively addressing the limitations of previous technologies.
Implementation Method 1
a method using an arc PVD apparatus where the substrate temperature is controlled above 200°C to form thick hard carbon films
Implementation Method 2
with alternating layers of low-temperature and high-temperature deposited hard carbon layers to achieve a balanced sp2/sp3 ratio
Data Source
Figure 1~2
Figure 3A~3B
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AI summary
The purpose of the invention is to provide technology, which, in addition to being capable of forming thick hard carbon films of excellent durability even using PVD, is able to establish both chipping resistance and abrasion resistance in the formed hard carbon film and able to improve low friction properties and peeling resistance. Provided is a coating film to be coated on the surface of a substrate, the coating film having a total film thickness of greater than 1 µm to 50 µm wherein: when a cut surface is observed using bright field TEM images, white hard carbon layers that are shown as relatively white and black hard carbon layers that are shown as black are alternately laminated in the thickness direction; and the white hard carbon layers have regions that have grown in a fan-shape in the thickness direction. Provided is a coating film manufacturing method for forming the coating film on the surface of a substrate using PVD, wherein conditions for film formation on the substrate are controlled so that the substrate repeatedly alternates temperature increase and temperature decrease between a low temperature range of greater than 50°C to 200°C and a high temperature range of greater than 200°C to 300°C, and the substrate is rotated and/or made to revolve.