What is Vickers Hardness Testing?

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Hardness, as a characteristic of a given material, is defined as the resistance to indentation. In other words, it’s the material’s ability to resist plastic deformation from another source. Think of it as a dent in a car after an accident. When you measure the depth of indentation, you get hardness. The smaller the deformation, the harder the material is.

There are many ways to measure or test the depth of the indentation, also known as indentation hardness value. In this article, we focus on the Vickers hardness tester, commonly referred to as microhardness testing method.

The Vickers testing method is an optical measurement system that uses a diamond indenter to make an indentation in a given material. The diamond is a right pyramid with a square base, where the opposite diagonal faces are angled at 136 degrees. The pyramid side of the diamond indenter is applied to the test subject at approximately 120 kilograms-force for about 10 to 15 seconds and then seamlessly removed.

To get the hardness value, you have to measure the two diagonals of the indentation left behind at the surface of the material once you remove the indenter. The Vickers hardness is therefore obtained by dividing the kgf load (F) by the square area of the deformation (d2).

Standard Test Methods for Vickers Hardness Testers

These standard methods provide the requirements for Vickers hardness machines and procedures for performing Vickers tests.

  1. Principle of the test. When doing a Vickers hardness test, most materials will show some elastic recovery after the indenter is removed. However, the general principle of the test is to assume that the indentation retains the shape of the indenter even after it’s removed.
  2. Testing machines. The Vickers testing machine should support the test subject, control the movement of the indenter into the specimen under a preselected load and have a light microscope to select the best location and measure the size of the indentation produced by the test.
  3. Verifications. All testing machines, measuring devices and indenters must be verified periodically before performing the hardness test.
  4. Test piece. There is no standardized size or shape for a Vickers test specimen. However, to give optimum accuracy of measurement, the specimen must be prepared and polished so as to be free of any defects that can affect the indentation.

What’s the Application of Vickers Hardness Tester?

For quality testing and other procedures such as welding, hardness testing is critical. Hardness testers allow you to evaluate the ductility, strength and wear resistance that will help you know if the material is suitable for a specific purpose.

The Vickers testing method is useful for testing a wide variety of materials, including metals, ceramics and composites. It is considered an easy method compared to other hardness tests because the size of the indenter does not affect the required calculations.

Because the indentation is so small, the test is applicable even in measuring very thin materials like foils. It can also be useful for measuring microstructures, or small parts to determine the hardness change profile. The test method covers the entire hardness range, so it can be used to test any material, whether hard or soft, and give accurate results.

Vickers hardness testing is used in many industries to determine the right material to use when manufacturing machinery or testing wear and tear. The material reporting the least deformity is chosen where hardness and durability are needed. The incredible thing is that you can use the Vickers test on both micro and macro hardness properties up to 50kgs test load.

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