Vickers hardness test according to DIN EN ISO 6507
The DIN EN ISO 6507 series of standards is the internationally authoritative basis for the Vickers-Hardness testing of metallic materials. The actual testing procedure is governed by DIN EN ISO 6507-1: This part specifies test forces, procedures, and evaluation for metallic materials, hard metals, sintered carbides, and metallic and other inorganic coatings. In quality assurance, incoming goods inspection, and laboratories, this standard serves as a central reference because it makes results comparable across the entire hardness range: from soft non-ferrous metals to hardened tool steel. The current version of the testing procedure is DIN EN ISO 6507-1:2024-01, supplemented by parts 2 to 4 of the standard series.
Key facts at a glance
- DIN EN ISO 6507 defines the Vickers-Hardness testing method for metallic materials, hard metals and inorganic coatings.
- The intruder is a diamond pyramid with a surface angle of 136° at the tip.
- The standard distinguishes three test force ranges: Macro, small force and micro range.
- The Vickers hardness value (HV) is calculated optically from the two diagonals of the permanent impression.
- Because of the small impressions, the method is considered a practically non-destructive hardness test.
- In practice, surface hardness (RHT) is determined by hardness profile measurements according to ISO 6507.
- The series of standards includes four parts and covers testing procedures, testing machines, hardness comparison plates and conversion tables.
Scope of DIN EN ISO 6507
DIN EN ISO 6507 specifies the Vickers indentation test for metallic materials. This includes conventional structural steels, tool steels, stainless steels, non-ferrous metals, as well as hard metals and other sintered carbides. Since the 2024 edition, metallic and other inorganic coatings have also been explicitly included in the scope. The permissible range for the diagonal length of the indentation is between 0,020 mm and 1,400 mm. For smaller indentations, ISO 14577-1 (instrumented indentation testing) applies; internationally, ASTM E384 covers the micro range and ASTM E92 covers the standard and low force range.
Typical applications include testing thin layers and films, workpiece edges, and surface-hardened components. ISO 6507 is also the reference method for hardness profile measurements in cross-sections, for example, on case-hardened gears or nitrided shafts.
The standard series consists of four parts: Part 1 describes the test procedure, Part 2 the verification and calibration of the testing machines, Part 3 the calibration of hardness comparison plates, and Part 4 contains tables for determining the hardness values from the measured diagonals.
Test principle of the Vickers hardness test
In the Vickers test, a right diamond pyramid with a square base and a face angle of 136° at the apex is pressed vertically into the sample surface with a defined test force. After the holding time has elapsed, the test force is removed and the resulting indentation is optically measured. The evaluation is based on the two diagonals d1 and d2 of the square indentation. The Vickers hardness is calculated from the arithmetic mean d. The larger the indentation for the same test force, the softer the material. For very thin layers, where a Vickers indentation would be too wide laterally, an alternative method can be used. Button-Insert intruder; the calculation is performed analogously.
Calculation of Vickers hardness (HV)
The Vickers hardness is calculated as the quotient of the applied test force and the surface area of the permanent impression:
HV = 0,1891 × F / d²
Here, F is the test force in Newtons and d is the mean diagonal of the indentation in millimeters. The factor 0,1891 originates from the historical definition of the method, when the test force was still specified in kiloponds (kp). It contains the reciprocal of 9,81 (conversion from Newtons to kgf) as well as the geometry factor of the pyramid. The calculated HV value is a dimensionless parameter that is always specified together with the test method and the applied test force.
Test force ranges and HV designation according to ISO 6507
DIN EN ISO 6507 divides the Vickers hardness test into three ranges according to the applied test force. The choice of range depends on the component being tested, the material thickness, and the desired level of detail in the result.
| Testing staff area | Testing officer F | HV area |
|---|---|---|
| Macro area | F ≥ 49,03 N | HV5 to HV100 |
| Small force area | 1,961 N ≤ F < 49,03 N | HV0,2 to < HV5 |
| micro-area | F < 1,961 N | < HV0,2 |
The macro range is the standard for testing entire components and larger samples. The micro range is used for hardness profile measurements, weld inspections, and smaller components. The micro range is used for thin films, individual phases in the microstructure, and fine structure investigations.
The standard prescribes a fixed abbreviation for the results documentation. A complete hardness value includes the numerical value, the abbreviation HV, the test force in kgf, and, if required, the holding time in seconds.
Example: 440 HV 30/20
The information means:
- 440: measured hardness value
- HV: Vickers test with diamond pyramid 136°
- 30: Test force in kgf (equivalent to 294,2 N)
- 20: Holding time in seconds (only to be specified if outside the target range of 10 s to 15 s)
Procedure and requirements for the examination
The procedure for a Vickers hardness test according to ISO 6507 is clearly structured. First, the specimen is prepared and positioned flat on the test table. The indenter is lowered onto the surface at a defined speed, and the test force is increased smoothly to its final value within the target time of 2 to 8 seconds. The test force is then held for a dwell time of 10 to 15 seconds. After the load is released, the two diagonals of the indentation are optically measured, and the HV value is calculated using the Vickers formula. In modern instruments, a camera with image analysis software automatically performs the diagonal measurement and documents the results.
For a result to comply with standards, several requirements for the sample and test environment must be met:
- Surfaceflat, smooth, free of scale, oil and foreign matter; polished for low-power and micro applications
- Minimum sample thickness: 1,5 times the indentation diagonal
- Minimum distances for steel, copper and copper alloys: at least 2,5 d to the sample edge, at least 3 d between two impression centers
- Minimum distances for light metals, lead, tin and their alloys: at least 3 d to the sample edge, at least 6 d between two impression centers
- Test temperatureOperating temperature: 10 °C to 35 °C, reference range: 23 °C ± 5 °C
- Testing machine: verified and calibrated according to DIN EN ISO 6507-2
If these specifications are not met, material compaction, cold working, or surface disturbances will distort the result.
Determine surface hardness (RHT) according to ISO 6507
There is no independent testing standard for surface hardness. In practice, it is determined via hardness profile measurements using the Vickers method according to ISO 6507. Additionally, DIN EN ISO 2639 governs the determination of the case hardening depth (CHD) on case-hardened components and also specifies limit hardness and evaluation rules. Vickers is the preferred method for this task because the small, clearly defined indentations allow for precise positioning in the cross-section and reliable correlation with the depth.
In addition to the surface hardening depth, other hardening depths relevant in heat treatment can be determined using the same procedure:
- CHD / Eht (Case hardening depth): Depth of the carburized and hardened surface zone
- SHD / Rht (Surface hardening depth): Depth after surface hardening (e.g., induction, flame)
- NHD / Nht (Nitriding case depth): Depth of the nitrided surface zone
- CD / At (Carburization depth): Depth of the carburized layer without hardness specification
- CLT / VS (Compound layer thickness): Thickness of the white compound layer in nitrided components
Hardness curve in cross-section
For hardness profile measurement, the component is cut perpendicular to the hardened surface zone, hot embedded, ground, and polished. Vickers indentations are then made in a row perpendicular to the surface, starting near the surface zone and progressing incrementally towards the core. The spacing between the indentations must comply with the minimum distances specified in ISO 6507 to prevent work hardening of adjacent indentations. Typical test forces are HV1 or HV0,5, and in some cases HV0,3. The measured HV values are plotted against the depth to produce the hardness profile curve.
Limit hardness and Rht value
The limiting hardness is the hardness value that separates the hardened surface zone from the softer core area. For case-hardened components, DIN EN ISO 2639 specifies a standard hardness of 550 HV1, unless another value has been agreed upon. The Rht value indicates the depth from the surface at which the hardness profile falls below the limiting hardness. It is typically given in millimeters. In practice, case-hardened gears with a defined Rht are a standard application, as are nitrided shafts, where the Nht is determined using the same method. Fully automatic Vickers hardness testers with a motorized XY table and image analysis are used to automate these measurements.
Suitable hardness testing equipment for ISO 6507
SCHÜTZ+LICHT is the exclusive German distributor for INNOVATEST, one of the world's leading manufacturers of hardness testing equipment. A wide portfolio is available for Vickers hardness testing according to ISO 6507, ranging from manual laboratory instruments to fully automated testing systems with motorized XY tables, image analysis software, and integrated hardness profile analysis.
The appropriate configuration depends on the application: For individual tests in the laboratory, a manual Vickers tester in the small or macro force range is sufficient. For serial hardness profile measurements on case-hardened, nitrided, or induction-hardened components, fully automated systems with camera measurement and standard-compliant evaluation according to ISO 6507 and ISO 2639 are recommended.
Are you unsure which device is right for your application? Our application engineers will advise you, independent of the manufacturer, on the testing task, level of automation, and test force range. We also handle DAkkS calibration, maintenance, and training for your staff.
Frequently asked questions about the Vickers hardness test according to ISO 6507
When is the Vickers hardness test preferable to the Rockwell or Brinell methods?
Vickers is the right choice when testing very hard materials, thin layers, small components, or measuring hardness profiles in cross-sections. The method covers the entire hardness range from very soft to extremely hard with a single indenter. Brinell It is better suited for inhomogeneous, coarse structures with a larger required indentation area. Rockwell It is faster and can be performed without optical evaluation, and is therefore frequently used in serial testing of homogeneous components.
How often does a Vickers hardness tester need to be calibrated according to ISO 6507?
The standard distinguishes between routine checks by the user and indirect verification. Routine checks using hardness reference plates are generally performed daily before testing begins. Indirect verification according to DIN EN ISO 6507-2 is typically carried out annually by an accredited calibration laboratory, as well as after every repair or major modification of the testing equipment.
What role do hardness comparison plates play in the Vickers test?
Hardness comparison plates are reference pieces with a certified hardness value. They are used for routine daily checks of the testing machine and thus form the basis for traceable results. Their calibration is regulated in DIN EN ISO 6507-3. The plate is always used in the appropriate hardness range and with the same test force as the subsequent test.
Is the Vickers test truly non-destructive?
Strictly speaking, every hardness test using an indenter is a destructive test, as it creates a permanent indentation. In practice, however, Vickers is considered low-destructive or practically non-destructive because the indentations are very small at low and medium test forces and generally do not impair the component's function. The indentation can be removed by grinding and polishing if necessary.
Can a Vickers hardness value be converted into tensile strength?
Yes, an approximate conversion is possible according to ISO 18265. Conversion tables between HV, HB, HRC and tensile strength Rm are provided there for unalloyed and low-alloy steels. These values are guidelines and do not replace a tensile test according to ISO 18265. ISO 6892-1For high-alloy steels, non-ferrous metals or cast materials, the conversions are only partially or not at all applicable.
