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기술정보 기술설명

기술정보

Adhesion Strength

Relationship Between Indentation Test and Adhesion Strength
The indentation test is a method used to evaluate the mechanical properties of composite materials with thin film (coating) layers on a substrate. The adhesion strength between the film and the substrate can be quantified through changes in indentation hardness. Maintaining the indentation depth at approximately one-tenth of the film thickness minimizes the influence of the substrate and allows for an accurate evaluation of the film’s hardness. Conversely, if the indentation depth exceeds one-tenth of the film thickness, both the substrate and the film deform, affecting the measurement of the adhesion interface due to the deformation reaction at the interface.
1Interface Confinement Effect

Weak Adhesion: If the adhesion strength is weak, the film and substrate respond independently to the indentation load, causing a strain discontinuity at the interface. This results in a sharp change in the load-displacement curve.

Strong Adhesion: With strong adhesion, the strain is continuously distributed, and additional plastic deformation energy is required, increasing the composite’s hardness. Strong adhesion induces compressive stress at the interface, as the film's deformation is constrained by the substrate.

Interface Confinement Effect
2Correlation Between Interface Compressive Stress and Adhesion Strength

Compressive stress at the film-substrate boundary is an important indicator of adhesion strength. High compressive stress indicates a strong mechanical or chemical bond, reducing the likelihood of delamination and strengthening structural integrity. The greater the adhesion strength, the higher the load required to achieve the same indentation depth, serving as a criterion for evaluating adhesion strength in indentation testing.

Correlation Between Interface Compressive Stress and Adhesion Strength
3Quantification of Adhesion Strength Through Indentation Load Analysis

The load required to achieve a set indentation depth serves as the basis for evaluating composite hardness and adhesion strength. A composite with strong adhesion requires a higher load to achieve the same indentation depth, which can be used to quantify the adhesion strength.

Hard Films: The adhesion strength of hard films is assessed using the scratch test, and when a soft substrate is coated with a thin film, the results show trends similar to those of the IIT method.

Soft Films: For soft films, the film may deform easily during the scratch test, so a pull-off test can be conducted alongside the indentation test to evaluate adhesion strength. The results of these tests also exhibit similar trends.

Advantages of the Indentation Testing Method
간편한 시험

Simple Test: Adhesion strength can be evaluated using a single indentation test without the need for additional equipment.

재현성

Reproducibility: The indentation load is preciselyadjustedaccording to changes in adhesion strength, providing reproducible results.

정확한 평가 위치

Accurate Evaluation Points: Unlike the scratch test, a single indentation can evaluate the adhesion strength at specific points, and mapping can reveal the distribution of adhesion strength across different film locations.

다양한 필름에 적용 가능

Applicable to Various Films: The method can be applied to both hard and soft films.

비파괴적 시험

Non-Destructive Test: Indentation load can be adjusted locally, allowing the test to be performed without damaging the overall film condition.

실시간 공정 평가

Real-Time Process Evaluation: The method allows for real-time evaluation of adhesion strength changes during the manufacturing process.

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