🔩 Vickers hardness of metals and coatings — pyramidal indenter, measurement of the indentation diagonals
In short
A diamond indenter in the form of a right pyramid with a square base (angle between opposite faces 136°) is forced into the surface of the test piece and, after removal of the force, the diagonals of the indentation are measured; hardness HV ≈ 0. The test is performed according to PN-EN ISO 6507-1:2024-04; Force ranges: F ≥ 49.03 N (HV 5 and above); 1.961 N ≤ F < 49.03 N (low force); 0.009807 N ≤ F < 1.961 N (microhardness). The procedure comprises 8 steps; it is used for: Hardness measurement of steel, cast steel, non-ferrous metals and hardmetals, Assessment of the effectiveness of heat treatment and thermochemical treatment (hardening, tempering, carburising, nitriding), Determination of the depth of the hardened layer from the hardness distribution on a cross-section.
At a glance
- Standard: PN-EN ISO 6507-1:2024-04
- Category: Materials and NDT
- Procedure steps: 8
- Indenter: Diamond, right pyramid with a square base, angle between opposite faces nominally 136°
- Force ranges: F ≥ 49.03 N (HV 5 and above); 1.961 N ≤ F < 49.03 N (low force); 0.009807 N ≤ F < 1.961 N (microhardness)
- Typical forces: HV 5 — 49.03 N; HV 10 — 98.07 N; HV 20 — 196.1 N; HV 30 — 294.2 N (recommended for hardmetals); HV 50 — 490.3 N; HV 100 — 980.7 N
Overview
The standard specifies the method for the Vickers hardness test for three ranges of test force, for metallic materials — including hardmetals — and for metallic and other inorganic coatings. The method applies to indentation diagonal lengths from 0.020 mm to 1.400 mm; determining hardness from smaller indentations is outside the scope of the standard, because the results carry a large uncertainty resulting from the limitations of optical measurement and imperfections of the tip geometry (ISO 14577-1 is used for smaller indentations).
The fifth edition, ISO 6507-1:2023, together with ISO 4545-1:2023, replaces ISO 4516:2002, ISO 4545-1:2017 and ISO 6507-1:2018; the scope was extended to metallic and other inorganic coatings (electrodeposited, autocatalytic, sprayed and anodic coatings on aluminium), and the requirements for coatings were gathered in Annex H. The method does not apply to coatings thinner than 0.030 mm when measured perpendicular to the coating surface and thinner than 0.100 mm when measured on a cross-section.
Force ranges: Vickers hardness test for F ≥ 49.03 N (symbol HV 5 and above), low-force test for 1.961 N ≤ F < 49.03 N (HV 0.2 to below HV 5) and microhardness test for 0.009807 N ≤ F < 1.961 N (HV 0.001 to below HV 0.2). In the laboratory exercises of the Lublin University of Technology the method is carried out on an HPO-250 hardness tester (Vickers-Brinell) on steel test pieces after annealing, hardening, tempering, carburising and nitriding, and on hardmetals.
Method principle
A diamond indenter in the form of a right pyramid with a square base and with a specified angle between opposite faces at the vertex (nominally α = 136°) is forced into the surface of the test piece, and after removal of the force F the lengths of the diagonals of the indentation left in the surface are measured. Vickers hardness is proportional to the quotient of the test force and the sloping area of the indentation, taken as a right pyramid with a square base and with the same vertex angle as the indenter: HV = (1/gn) · 2F·sin(α/2)/d², and for the nominal angle α = 136° approximately HV ≈ 0.1891 · F/d², where d is the arithmetic mean of the two diagonals in millimetres and gn = 9.80665 m/s² (conversion factor from kgf to N). To reduce uncertainty, hardness may be calculated from the actual mean angle of the indenter.
Applications
- Hardness measurement of steel, cast steel, non-ferrous metals and hardmetals
- Assessment of the effectiveness of heat treatment and thermochemical treatment (hardening, tempering, carburising, nitriding)
- Determination of the depth of the hardened layer from the hardness distribution on a cross-section
- Hardness testing of metallic and inorganic coatings, also on cross-sections
- Study of the relationship between structure and hardness of a material (laboratory exercises, materials testing)
Key parameters
| Parameter | Value |
|---|---|
| Indenter | Diamond, right pyramid with a square base, angle between opposite faces nominally 136° |
| Force ranges | F ≥ 49.03 N (HV 5 and above); 1.961 N ≤ F < 49.03 N (low force); 0.009807 N ≤ F < 1.961 N (microhardness) |
| Typical forces | HV 5 — 49.03 N; HV 10 — 98.07 N; HV 20 — 196.1 N; HV 30 — 294.2 N (recommended for hardmetals); HV 50 — 490.3 N; HV 100 — 980.7 N |
| Diagonal range | 0.020 mm to 1.400 mm; resolution of the measuring system 0.0004 mm for d < 0.080 mm, 0.5 % of d for d ≥ 0.080 mm |
| Test piece thickness | At least 1.5 × the length of the indentation diagonal (hardmetals: min. 1 mm); after the test no visible deformation on the underside of the test piece |
| Test temperature | 10 °C to 35 °C; under controlled conditions (23 ± 5) °C |
Standard
- Standard number
- PN-EN ISO 6507-1:2024-04
- Title (PL)
- Metale — Pomiar twardości sposobem Vickersa — Część 1: Metoda badania
- Title (EN)
- Metallic materials — Vickers hardness test — Part 1: Test method
Step-by-step procedure
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Surface preparation
Carry out the test on a smooth, even surface, free of scale and contaminants and completely degreased. Prepare the surface so as not to change its hardness through heating or cold working; for microhardness polishing or electropolishing is recommended. For hardmetals the layer removed is not less than 0.2 mm.
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Selection of conditions
Select the highest permissible test force depending on the thickness of the test piece or of the layer tested and on the expected hardness (minimum thicknesses — Annex A of the standard); the force must give diagonals not shorter than 0.020 mm. Determine the force duration, the minimum distances between indentations and from the edge of the test piece, and the accuracy of the diagonal measurement.
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Periodic check
Carry out the check according to Annex C within one week before use for each force used (recommended on the day of testing), always after a change of the indenter and recommended after a change of force.
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Positioning the test piece
Place the test piece on a rigid support with a clean surface so that it cannot move during loading. Support curved test pieces appropriately; for anisotropic materials take into account a possible difference in length of the two diagonals.
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Trial measurement and indentations
Carry out at least one trial measurement in accordance with the hardness tester instructions, then make 3 indentations on each test piece (practice of the Lublin University of Technology exercises).
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Measurement of the diagonals
Measure both diagonals of each indentation to an accuracy of ±0.001 mm; use the arithmetic mean of the diagonals of one indentation to calculate the hardness.
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Calculation of hardness
Calculate HV from the formula (HV ≈ 0.1891 · F/d²) or read it from tables; for cylindrical or spherical surfaces apply the corrections from Tables B.1–B.6 of the standard.
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Report
Give the results in a table, a sketch of the test pieces with the measurement locations marked, the selection of test conditions and a discussion of errors; in the report according to the standard also give the surface curvature if a correction was applied, and the temperature if the test was carried out outside the range 10–35 °C.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Vickers hardness tester | Capable of applying the specified forces in accordance with ISO 6507-2; in the exercises of the Lublin University of Technology an HPO-250 tester (Vickers-Brinell), maximum load 2452 N | — |
| Diamond indenter | Right pyramid with a square base according to ISO 6507-2 | — |
| Diagonal measuring system | Microscope with a graticule or a camera; magnification such that the diagonal occupies more than 25 % but less than 75 % of the field of view | — |
| Rigid specimen stage and supports | Clean, free of scale and contaminants; for test pieces of small cross-section a holder or mounting as for a metallographic section | — |
| Hardness reference standards (reference blocks) | For the periodic check according to Annex C of the standard | — |
| Test piece preparation station | Grinder, abrasive papers of grit 100–800, polishing with diamond suspension or electropolishing | — |
Health and safety (OHS)
- Diamond indenter and loading mechanism — do not put fingers under the plunger, clamp the test piece securely on the stage
- Grinding and polishing of test pieces: metal and abrasive dust — safety glasses, extraction or water circulation
- Sharp edges of test pieces and metallographic sections — gloves when handling
- Projection lamp and microscope illumination — do not look directly into the light source
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 6507-1:2024-04 — “Metallic materials — Vickers hardness test — Part 1: Test method”.
How does this method work?
A diamond indenter in the form of a right pyramid with a square base and with a specified angle between opposite faces at the vertex (nominally α = 136°) is forced into the surface of the test piece, and after removal of the force F the lengths of the diagonals of the indentation left in the surface are measured. Vickers hardness is proportional to the quotient of the test force and the sloping area of the indentation, taken as a right pyramid with a square base and with the same vertex angle as the indenter: HV = (1/gn) · 2F·sin(α/2)/d², and for the nominal angle α = 136° approximately HV ≈ 0.
What is the measuring range and accuracy?
Indenter: Diamond, right pyramid with a square base, angle between opposite faces nominally 136°; Force ranges: F ≥ 49.03 N (HV 5 and above); 1.961 N ≤ F < 49.03 N (low force); 0.009807 N ≤ F < 1.961 N (microhardness); Typical forces: HV 5 — 49.03 N; HV 10 — 98.07 N; HV 20 — 196.1 N; HV 30 — 294.2 N (recommended for hardmetals); HV 50 — 490.3 N; HV 100 — 980.7 N; Diagonal range: 0.020 mm to 1.400 mm; resolution of the measuring system 0.0004 mm for d < 0.080 mm, 0.5 % of d for d ≥ 0.080 mm.
How long does the test take?
The procedure comprises 8 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Vickers hardness tester, Diamond indenter, Diagonal measuring system, Rigid specimen stage and supports, Hardness reference standards (reference blocks), Test piece preparation station.
Where is this test used?
Hardness measurement of steel, cast steel, non-ferrous metals and hardmetals; Assessment of the effectiveness of heat treatment and thermochemical treatment (hardening, tempering, carburising, nitriding); Determination of the depth of the hardened layer from the hardness distribution on a cross-section; Hardness testing of metallic and inorganic coatings, also on cross-sections; Study of the relationship between structure and hardness of a material (laboratory exercises, materials testing).
What safety precautions apply?
Diamond indenter and loading mechanism — do not put fingers under the plunger, clamp the test piece securely on the stage; Grinding and polishing of test pieces: metal and abrasive dust — safety glasses, extraction or water circulation; Sharp edges of test pieces and metallographic sections — gloves when handling; Projection lamp and microscope illumination — do not look directly into the light source.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 6507-1.