Diamondlike Carbon Multilayer Film Adhesion and Wear Resistance
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Solution Overview
Problem
Existing methods for forming diamondlike carbon (DLC) films with high hardness face challenges in achieving both excellent adhesiveness to substrates and wear resistance, particularly when the DLC multilayer film thickness exceeds 3 µm, especially on substrates with varying hardness levels such as cemented carbide and iron-based materials.
Innovation Solution
A method involving a composite process using unbalanced magnetron sputtering to form a two-layer DLC film structure, with a first DLC film of lower hardness and a second DLC film of higher hardness, along with an intermediate layer, to enhance adhesiveness and wear resistance. The first DLC film is formed by sputtering, and the second DLC film is formed by cathode discharge type arc ion plating, with specific metal layers and amorphous layers to optimize substrate compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a DLC film with high hardness is formed to achieve excellent wear resistance, then wear resistance is improved, but adhesiveness to the substrate deteriorates due to extremely large internal stress
Solution Approach 1:
The DLC film is divided into multiple layers with different hardness levels. The first DLC film layer has lower hardness and serves as a stress buffer, while the second DLC film layer has higher hardness and provides wear resistance. This segmentation allows the system to achieve both good adhesiveness (through the softer first layer) and excellent wear resistance (through the harder second layer).
Solution Approach 2:
Different regions of the DLC film structure are assigned different properties. The first DLC film layer is designed with lower hardness to provide good adhesiveness to the substrate, while the second DLC film layer is designed with higher hardness to provide excellent wear resistance. This local differentiation of material properties resolves the contradiction between adhesiveness and wear resistance.
2Strength
If the thickness of the DLC film is increased to improve protective function, then wear resistance is improved, but internal stress accumulates causing film separation
Solution Approach 1:
The thick protective DLC film is segmented into multiple layers with different hardness levels. The first DLC film layer (thicker, softer) absorbs internal stresses, while the second DLC film layer (thinner, harder) provides the primary wear-resistant protective function. This segmentation enables the film to maintain stability even at greater total thickness.
3Reliability
If a mixed layer is formed to improve adhesiveness, then adhesiveness is improved, but the thickness of the mixed layer is limited to a narrow range
Solution Approach 1:
The first DLC film layer acts as an intermediary between the substrate and the second DLC film layer. It provides a transition zone that facilitates stress distribution and bonding, enabling good adhesiveness without requiring a separately formed mixed layer with tightly controlled thickness.
4Strength
If DLC film thickness is increased to 3 µm or more to provide adequate protection, then protective function is improved, but adhesiveness deteriorates due to increased whole stress
Solution Approach 1:
When the total DLC film thickness is 3 µm or more, the film is segmented into a first DLC film layer (softer, thicker) and a second DLC film layer (harder, thinner). The first layer serves as a stress buffer that prevents whole-film detachment, while the second layer provides the necessary protective function. This segmentation enables thick films to maintain both adhesiveness and protective capability.
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 achieves enhanced adhesiveness and wear resistance for DLC multilayer films, ensuring strong bonding to substrates with varying hardness levels, even when the film thickness exceeds 3 µm, thereby improving the durability and reliability of DLC films on a wide range of materials.
Implementation Method 1
forming a first diamondlike carbon film on the intermediate layer by sputtering
Implementation Method 2
forming a second diamondlike carbon film on the first diamondlike carbon film by cathode discharge type arc ion plating
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A diamondlike carbon hard multilayer formed film body comprises a substrate, a diamondlike carbon film mainly composed of diamondlike carbon, and an intermediate layer between the substrate and the diamondlike carbon film. The diamondlike carbon film is composed of, in order from the substrate side, a first diamondlike carbon film and a second diamondlike carbon film. The surface hardness of the first diamondlike carbon film is within the range from not less than 10GPa to not more than 40GPa based on nanoindentation test, and the surface hardness of the second diamondlike carbon film is within the range from more than 40GPa to not more than 90GPa based on nanoindentation test. According to such a structure, even if a DLC multilayer containing high-hardness DLC film on the outermost surface side is formed in a thickness of not less than about 3 µm on a substrate of a wide range extending from a material with high hardness such as cemented carbide to an iron-based material with low hardness, excellent adhesion to both the substrate and the DLC film can be ensured in addition to excellent wear resistance.