The Vickers hardness test is suitable for a wide range of applications, including micro hardness testing. On this page, you can find a description of the Vickers hardness test, practical information on how to apply it and a list of our micro hardness testing machines for Vickers.
The Vickers hardness test at a glance:
Ideal for micro hardness testing
Can be used for case hardness depth measurement, Jominy testing and hardness testing of welds
The Vickers hardness test is a versatile hardness test method, used for both macro and micro hardness testing. It has a broad load range, and is suitable for a wide range of applications and materials.
The Vickers hardness test is often regarded as easier to use than other hardness tests: The process can be performed on a universal or micro hardness tester; the required calculations are independent of the size of the indenter; and the same indenter (a pyramidal diamond) can be used for all materials, irrespective of hardness.
The Vickers Hardness calculation
The Vickers Hardness (HV) is calculated by optically measuring the diagonal lengths of the impression left by the indenter. The measurements are converted to HV using a table or formula.
1. Place your sample on the stage. 2. Click and drag the mouse to move the sample into position. 3. Scroll to focus. 4. Select the test method and load. 5. Choose an objective and job name. 6. Use the overview camera to position the indenter. 7. Start the test.
Before placing the sample material in the micro hardness testing machine, you should ensure it is correctly prepared.
The required surface condition for the Vickers hardness test depends on the load used.
Macro hardness testing (loads higher than 1 kgf)
Surface should be ground
Micro hardness testing (loads below or equal to 1 kgf)
Surface should be mechanically polished or electropolished
Loads
Indentation time: 10-15 seconds
Sample thickness ASTM: At least 10 times the indentation depth
Sample thickness ISO: At least 1.5 times the diagonal length
Indent spacing
Regardless of the micro hardness tester you use, when you perform a Vickers hardness test, your indentation will deform the surrounding material and alter its properties. In order to avoid misinterpretations of perceived hardness, the Vickers hardness testing standards prescribe a certain distance between multiple indentations.
Steel and copper
At least 3 diagonal widths between indentations
Lead, zinc and aluminum
At least 6 diagonal widths between indentations
Diagonal widths
To ensure accurate reading of the indents, the Vickers hardness testing standards prescribe a minimum diagonal width of 20 µm.
For instance, this implies that CHD (see below) measurements using less than HV0.2 should generally be avoided, as they will produce indents smaller than 20 µm.
Vickers test methods and applications
Below you can see an overview of the Vickers hardness test methods and the most common applications.
Case hardness depth (CHD) measurement
Surface Hardness
Hardness testing is often used to evaluate the hardness depth of surface-hardened steels. This is done by making a series of hardness impressions from the edge of the cross-sectioned sample towards the center. The hardness progression is plotted in a graph and the distance from the surface to the hardness limit (HL) is calculated.
When performing a hardness progression, it is important to observe the rules for indent spacing. Edge retention is also required during the mechanical preparation of samples to ensure an accurate measurement of CHD.
Case depth = Distance from surface to hardness limit
How to calculate CHD
There are different ways to determine the hardness limit. There are therefore different ways to calculate the CHD value. The procedure you choose depends on the hardening process used. The most common calculation methods are listed below.
1. Carburized or carbonitrided parts (EN ISO 2639)
Hardness limit = 550 HV
CHD (Eht) = Distance from the surface to the point where the hardness is 550 HV
2. Induction or flame-hardened parts (EN 10328 & ISO 3754)
Hardness limit = 80% x (minimum) surface hardness
CHD (Rht) = Distance from the surface to the point where hardness is 80% of the (minimum) surface hardness
3. Nitrided parts (DIN 50190-3)
Hardness limit = Core hardness + 50 HV
CHD (Nht, NCD) = (Maximum) distance from the surface to the point where hardness is 50 HV above core hardness
Example of CHD progression
CHD measurement displaying a CHD value of 0.95 mm at a hardness limit of 550 HV1
Different ways of calculating CHD
Vickers versus Knoop hardness testing
In most cases, the Vickers hardness test is used to determine hardness in materials in the micro hardness test load range. However, the Knoop hardness test is often used when hardness testing thin layers, such as coatings, or to overcome the problem of cracking in brittle materials.
When selecting which test to use, you should consider relevant standards, as well as the usual criteria when choosing between different types of hardness test.
The Jominy test (End Quench Test) is a standardized test procedure used to determine the hardenability of steel, and it can be performed using any Vickers micro hardness tester.
The procedure is described in the following standards: ASTM A255 / ISO 642 / DIN 50191 / BS 4437
The Jominy test involves heating a cylindrical steel test piece to an austenitizing temperature (~980°–1010°C) and quenching (cooling) from one end, with a controlled and standardized jet of water. After quenching, the hardness is measured at intervals taken from the quenched end. The test method used is either HRC or HV30.
The hardness variation along the test surface is a result of microstructural variation that arises as the cooling rate decreases with the distance from the quenched end. The harder the material at a given distance from the end, the higher the hardenability of the steel.
Both the Vickers and the Rockwell hardness tests are often used for Jominy testing. When selecting which to use, pay attention to the relevant standards, as well as the usual criteria when choosing between different types of hardness test.
Hardness testing of welds is a subgroup of the Vickers hardness test. The purpose of these hardness tests is to evaluate the strength of the weld, with particular focus on hardness around the heat-affected zone (HAZ). This is because the hardness in and around the HAZ can help evaluate the brittleness of the weld and can therefore help you determine whether or not the weld has the strength you require. Hardness testing of welds can be performed on any Vickers micro hardness testing machine.
When hardness testing of welds, a series of measurements are made in a given pattern at a specific distance from the sample edge or top of the weld. The progression of the hardness values can then be plotted in a graph.
Hardness testing is key in most quality control procedures. That’s why we provide a complete range of hardness testing machines, including micro hardness testing testers for Vickers.
As one of the leading Vickers hardness tester manufacturers, all our universal, macro and micro hardness machines are designed for accuracy, ease of use and long-term reliability.
If you would like to know more about the hardness testing methods for metallic and other materials, including a full definition of hardness testing, the different applications of hardness tests and how to prepare for hardness tests, download our resources.
Please do not hesitate to ask if there are things you haven’t found answers to. You are also welcome to ask us, in general, about how you can optimize your operation.
