Vickers

Vickers Hardness Testing Method

The Vickers method is a static hardness testing technique renowned for its versatility and precision.
Below are its detailed technical aspects:

  1. Standardisation:
    • Governed by ISO 6507 and ASTM E92, the Vickers method is a globally standardised procedure, ensuring consistent results across applications.
  2. Test Load Range:
    • The Vickers method supports loads ranging from 1 gf to 100 kgf, accommodating a wide spectrum of applications, from micro-hardness to macro-hardness testing.
    • Typical load values include 10 gf, 100 gf, 1 kgf, and 50 kgf, depending on the material and testing requirements.
  3. Measurement Principle:
    • The Vickers method is an optical technique, where the diagonals of a diamond-shaped indentation are measured under a high-magnification microscope.
    • The Vickers Hardness (HV) is calculated using the formula: HV=1.854⋅Fd2HV = \frac{1.854 \cdot F}{d^2}HV=d21.854⋅F​ where F is the applied load in kgf, and d is the mean diagonal length of the indentation in millimeters.
    • The precision of diagonal measurements allows the method to handle very small or delicate specimens.
  4. Indenter Design:
    • The indenter is a pyramid-shaped diamond with a square base and an angle of 136° between opposite faces, designed to ensure uniform stress distribution during indentation.
    • Its geometry is suitable for testing materials of varying hardness, from soft metals to hard ceramics.
  5. Optical Requirements:
    • Measurements are typically made using a microscope with high magnification, often ranging from 400x to 1000x, to ensure accuracy.
    • Modern systems may incorporate digital imaging and automated measurement tools to minimise human error and enhance repeatability.
  6. Specimen Preparation:
    • Specimens must have a polished, flat surface to ensure clear visibility of the indentation. Surface irregularities or coatings can affect accuracy.
    • A minimum thickness of at least 10 times the depth of the indentation is recommended to avoid substrate interference.
  7. Applications:
    • Suitable for a wide variety of materials, including metals, alloys, ceramics, composites, and thin coatings.
    • The method is particularly valued in micro-hardness testing for applications like thin films and small components in electronics or medical devices.
  8. Advantages:
    • The ability to use a single indenter for all test loads simplifies the testing process.
    • The small size of the indentation allows for testing of small parts and thin layers.
  9. Limitations:
    • The method requires meticulous specimen preparation and optical precision, which can be time-consuming.
    • Indentation size may be difficult to measure on rough or non-uniform surfaces.

The Vickers method’s versatility, high accuracy, and broad load range make it one of the most widely used hardness testing techniques across various industries, including research, manufacturing, and quality control.