Choosing the appropriate Vickers hardness tester test force requires a comprehensive judgment based on three core factors: sample characteristics, hardness range, and standard requirements, to ensure that the indentation size is reasonable, the measurement results are accurate, and the sample is not damaged. Here are the specific points:

1、 Determine the minimum test force based on the thickness and size of the sample

Excessive testing force can easily cause deformation and puncture of the specimen (especially for thin film and coated specimens), while insufficient force can result in blurry indentation that is difficult to measure. The diagonal length of the indentation must be ≤ 1/10 of the sample thickness, and the distance between the indentation edge and the sample edge must be ≥ 2.5 times the diagonal length of the indentation.

Thin/foil material (thickness<1mm): choose a small test force (such as 0.098N, 0.245N) to avoid pressure penetration;

Conventional block specimen (thickness 3-10mm): optional medium test force (1.96N, 2.94N);

Thick and large pieces/metal components (thickness>10mm): Large test forces (9.8N, 49N) can be selected to improve the representativeness of the results.

2、 Match test force based on material hardness range

Different hardness materials have varying degrees of sensitivity to test force, and it is necessary to avoid shallow or deep indentation:

High hardness materials (such as quenched steel and hard alloys): When the hardness is ≥ 500HV, a large test force (4.9N-98N) is required to ensure clear and measurable indentation and reduce measurement errors;

Medium hardness materials (such as annealed steel, aluminum alloys): hardness 100-500HV, optional medium test force (1.96N-9.8N);

Low hardness/soft materials (such as pure copper and plastic): When the hardness is less than 100HV, use a small test force (0.245N-1.96N) to prevent excessive indentation from causing plastic deformation of the sample and affecting its authenticity.

3、 Adhere to industry standards and testing objectives

There are clear standard requirements for different application scenarios, which should be followed first:

Conventional testing of metal materials: According to GB/T4340.1 or ISO6507.1, the recommended test force is based on the thickness of the sample (such as a thickness of 2mm corresponding to 2.94N);

Coating/Coating Testing: According to GB/T9790, a small test force (0.098N-1.96N) should be used to avoid pressing into the substrate and ensure that only the hardness of the coating is measured;

Small parts/thin sections: such as bearing raceways and tool cutting edges, suitable for narrow testing areas using micro Vickers small test force (0.098N-0.98N).

4、 Reference instrument and pressure head specifications

The indenter of the Vickers hardness tester is a diamond regular pyramid (apex angle 136 °), and the test force range of instruments with different ranges is different:

Micro Vickers hardness tester: test force 0.0098N-9.8N, suitable for small and thin specimens;

Macro Vickers hardness tester: Test force 9.8N-980N, suitable for large and high hardness specimens.

It is necessary to ensure that the selected test force is within the effective range of the instrument and that the indenter is not worn (wear can cause indentation distortion).

5、 Principle of adjustment in special circumstances

If the surface of the sample is rough: the test force can be appropriately increased to make the indentation clearer and reduce the influence of surface smoothness on measurement;

Comparative experiment: Fixed test force is required during multiple tests to ensure comparability of data;

When uncertain: prioritize pre testing with a smaller test force, observe the indentation status (whether it is clear and whether the sample is damaged), and then adjust to the appropriate value.