Vickers Hardness Testing
Practical guide for choosing the right test force, preparing the sample, reading the indentation and avoiding common measurement errors
Vickers hardness testing is one of the most useful hardness testing methods when you need to measure a specific point, a small area, a thin layer, a heat-treated surface or a polished metallographic section.
Unlike Rockwell testing, which gives a direct value from penetration depth, the Vickers method requires an optical measurement of the indentation diagonals. This makes the method very flexible, but also more sensitive to sample preparation, focus, surface finish and operator procedure.
In practical terms, Vickers is the right choice when you need to test:
- thin or small components
- case hardened parts and CHD profiles
- welds and heat affected zones
- coatings and surface treatments
- polished metallographic samples
- laboratory samples where the exact test position matters
This page provides a practical guide to Vickers hardness testing, focused on real testing conditions, sample preparation, force selection, indentation reading and common mistakes to avoid.
For a more technical and theoretical explanation, including Vickers and Knoop formulas, standards, verification and error tables, see: The Vickers and Knoop Hardness Test Theory 📘
For a general overview of hardness testing methods, standards and applications, see our Hardness Testing overview 👉
📌 Table of contents
- What is Vickers Hardness Testing?
- When should you use the Vickers test?
- How the Vickers test works in practice
- How to choose the right Vickers test force
- How to prepare the sample correctly
- How to read a Vickers indentation
- How to know if the result is valid
- Vickers testing for case depth and hardness profiles
- Standards for Vickers hardness testing
- Vickers vs Rockwell vs Brinell
- From method to equipment
- Why calibration and test blocks matter
- Vickers Hardness Testing – Mini FAQ
- Author & Technical Responsibility
- Contact our technical team
What is Vickers Hardness Testing?
Vickers hardness testing is an optical indentation method used to measure the hardness of a material by pressing a diamond pyramid indenter into the surface under a defined test force.
After the force is removed, the two diagonals of the indentation are measured. The hardness value is then calculated from the applied force and the average diagonal length.
In simple terms:
- a smaller indentation means a harder material
- a larger indentation means a softer material
- the result is expressed as HV followed by the test force used
For example, 700 HV 0.5 means that the Vickers hardness value is 700 and the test was performed with a test force of 0.5 kgf.
Never report a Vickers value as a number alone. Always include the test force. A value written as 700 HV 0.5 is complete; a value written only as 700 HV is incomplete for technical reports, audits and comparisons.
When should you use the Vickers test?
The Vickers test is useful when Rockwell (or Brinell) is too “large” or too fast for the level of detail required. It is especially suitable when the test point must be selected under a microscope or when the material has local hardness variations.
Use Vickers when you need to:
- measure hardness on a polished cross-section
- check a heat-treated layer
- measure a hardness profile from surface to core
- test small areas that cannot be tested reliably with Rockwell
- compare different zones of a weld
- measure thin or surface-treated materials
- perform microhardness testing in a laboratory
Avoid Vickers as the first choice when the surface is rough, the test must be extremely fast, or the part can be tested more easily with Rockwell or Brinell. Vickers is powerful, but it requires more preparation and more attention to the indentation image.
How the Vickers test works in practice
The practical Vickers test sequence is simple:
- Prepare the surface
The test area must be clean, flat and suitable for optical measurement. - Select the test force
The force must match the material, thickness, expected hardness and purpose of the test. - Focus the surface
The operator selects the test point under the optical system. - Apply the indentation
The diamond indenter is pressed into the material under the selected force. - Measure the diagonals
After unloading, both diagonals of the indentation are measured. - Check the indentation shape
The indentation must be clear, regular and far enough from edges or other indentations.
The most important practical difference compared with Rockwell is that the operator, camera or software must correctly identify the indentation corners. If the indentation cannot be measured clearly, the result should not be trusted.
Learn more:
Vickers test principle and formula 📘
How to choose the right Vickers test force
Choosing the correct test force is one of the most important practical decisions in Vickers hardness testing.
A force that is too high can produce an indentation that is too large, too deep or too close to the substrate in thin layers. A force that is too low can produce an indentation that is too small to measure reliably, especially if the surface is not perfectly polished.
As a practical rule:
- use lower forces for thin layers, coatings, case depth profiles and very small areas
- use higher forces for larger, homogeneous and well-supported samples
- make sure the indentation is large enough to be measured clearly
- make sure the indentation is not too large for the available test area
- check that spacing from edges and nearby indentations is sufficient
| Application | Practical force selection advice |
| Polished microstructure | Use low microhardness forces and verify that the indentation corners are clearly visible. |
| Case depth profile | Select a force that allows multiple indentations at controlled distances without overlap. |
| Thin coating | Use a low force and verify that the indentation is not influenced by the substrate. |
| Weld section | Use a force suitable for the width of the weld zones and heat affected areas. |
| General laboratory testing | Use the force required by the standard, specification or customer procedure. |
Do not choose the test force only because it is “commonly used”. The correct force depends on material thickness, expected hardness, indentation size, distance from edges and the purpose of the measurement.
How to prepare the sample correctly
Vickers hardness testing is highly dependent on surface preparation. Since the hardness value is calculated from the measured indentation diagonals, the surface must allow the operator or software to clearly identify all four corners.
The surface should be:
- flat
- clean
- stable
- free from oxide scale
- free from heavy scratches
- perpendicular to the indenter axis
- suitable for optical measurement
For macro Vickers testing, a properly ground or machined surface may be acceptable depending on the application. For micro Vickers testing, case depth profiles and coating measurements, a polished metallographic surface is normally required.
If the surface is rough or poorly polished, the indentation corners may be difficult to identify. This can create more error than the hardness tester itself.
For complete metallographic workflows, ATI also supports customers with machines for metallographic sample preparation.
If the indentation is not clear, do not try to “guess” the diagonal. Improve the surface preparation, adjust focus and illumination, or repeat the test on a better prepared area.
How to read a Vickers indentation
A good Vickers indentation should look regular, symmetrical and clearly defined. Both diagonals must be visible from corner to corner.
Before accepting the result, check that:
- all four corners are sharp and visible
- the two diagonals are reasonably consistent
- the indentation is not too close to an edge
- the indentation is not too close to another indentation
- there are no scratches crossing the indentation corners
- the image is properly focused
- the surface is not tilted
If the indentation appears stretched, distorted, out of focus or unclear, the result should be reviewed.
A Vickers indentation can be mathematically measured only if the corners are optically clear. If the operator cannot identify the corners with confidence, the result is weak even if the machine is perfectly calibrated.
How to know if the result is valid
A Vickers result should be considered valid only when the test conditions and indentation quality are acceptable.
A result may be questionable or invalid if:
- the indentation is too close to the edge of the specimen
- the indentation is too close to another indentation
- the surface is not flat or is not perpendicular to the indenter
- the specimen moved during the test
- the indentation corners are unclear
- the selected force is not suitable for the material thickness
- the surface preparation is too rough for the selected force
- the two diagonals differ significantly because of distortion or tilt
As a practical approach, when a value looks unexpected, repeat the test after checking preparation, focus, support and force selection. Do not immediately assume that the material is wrong.
Vickers testing for case depth and hardness profiles
Vickers testing is widely used for case hardness depth and hardness profile measurement because it allows a sequence of small indentations to be made at controlled distances from the surface.
This is common for:
- carburized layers
- nitrided layers
- induction hardened components
- weld heat affected zones
- surface treated steels
- thin hardened layers
In practice, the operator prepares a polished cross-section and performs a line of indentations from the surface toward the core of the material. The hardness values are then plotted against distance.
For this type of test, the most important practical points are:
- the surface must be polished and well supported
- the first indentation must not be too close to the edge
- spacing between indentations must be sufficient
- the selected force must allow a readable but not excessive indentation
- the test pattern should be planned before starting
Modern automatic Vickers hardness testers can simplify this process with motorized stages, predefined patterns, automatic indentation reading and case depth reporting.
For case depth profiles, the test force and indentation spacing must be chosen together. If the force is too high, the indentations may become too large and the profile may not fit correctly within the hardened layer.
Standards for Vickers hardness testing
Vickers hardness testing is governed by international standards that define test method, force application, indentation measurement, spacing, reporting and verification requirements.
Common reference standards include:
- ISO 6507 – Metallic materials — Vickers hardness test
- ASTM E92 – Standard Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
- ASTM E384 – Standard Test Method for Microindentation Hardness of Materials
Following the correct standard is essential for traceability, repeatability and comparability of results.
Learn more:
The Vickers and Knoop Hardness Test Theory 📘
Vickers vs Rockwell vs Brinell
Vickers is not always the fastest method, but it is often the most useful when the test area is small or when the hardness distribution must be evaluated locally.
| Method | Best practical use | Main advantage |
| Rockwell | Fast routine testing on suitable metal parts | Direct reading, fast cycle, minimal optical measurement |
| Brinell | Castings, forgings and inhomogeneous materials | Large indentation, good average over coarse structures |
| Vickers | Small areas, thin layers, case depth, welds and laboratory testing | Precise optical measurement and wide force range |
As a practical rule:
- choose Rockwell when speed and direct reading are the priority
- choose Brinell when the material is coarse, cast or structurally inhomogeneous
- choose Vickers when the test location, profile or small indentation is important
From method to equipment
Once the Vickers method and test force have been defined, the selection of the correct hardness tester becomes important.
ATI provides Vickers hardness testers for:
- microhardness testing
- low-force Vickers testing
- macro Vickers testing
- Knoop hardness testing
- case hardness depth profiles
- weld testing
- coating and surface layer evaluation
- laboratory and quality control applications
Depending on the configuration, a Vickers hardness tester can include manual or automatic indentation reading, motorized stages, automatic focus, predefined test patterns, CHD software and report generation.
Explore Vickers Hardness Testers 👉
Why calibration and test blocks matter
Reliable Vickers hardness testing requires not only a good instrument, but also proper verification and calibration.
Because the result depends on force application, indenter condition and optical measurement, regular checks are essential.
A good control process should include:
- periodic verification with certified Vickers hardness test blocks
- inspection of the indenter condition
- checking of the optical measuring system
- proper machine calibration
- documented traceability for audits and quality systems
ATI supplies certified hardness test blocks and provides ISO/IEC 17025 accredited calibration services for hardness testers and measuring systems.
For routine verification, use test blocks close to the hardness range and force level normally used in your laboratory. A check performed at a very different force or hardness level may not be representative of your real testing conditions.