Vickers Hardness Testing: Method, Formula, and ASTM E384
Representative Infinita Engineering Visual explaining the four-step workflow for Vickers Hardness Testing.What Is Vickers Hardness Testing?
Vickers hardness testing, governed by ASTM E92, determines material hardness by pressing a square-based diamond pyramid indenter into a surface under a known force and measuring the resulting indentation’s diagonal length. Unlike Rockwell, which measures indentation depth directly, Vickers measures the indentation’s surface area optically — a distinction that lets a single indenter type cover an unusually wide hardness range, from very soft metals to hardened tool steels.
Indenter Geometry
The Vickers indenter is a square-based diamond pyramid with a 136-degree included angle between opposite faces. Because the same indenter geometry is used across the entire force range (200 gf to 120 kgf under ASTM E92), Vickers produces a consistent hardness number for homogeneous materials regardless of which specific test force is applied — a key advantage over Brinell, where indenter-to-load ratio must be matched to material and thickness.
Test Procedure
- Prepare a flat, polished test surface free of scratches or surface contamination that could distort optical measurement of the indentation
- Select a test force appropriate to expected hardness and specimen thickness
- Apply the indenter under the selected force and hold for a specified dwell time, typically 10-15 seconds
- Retract the indenter and measure both diagonals of the resulting square indentation using a calibrated optical microscope or automated imaging system
- Calculate Vickers hardness (HV) from the applied force divided by the surface area of the indentation, using the average of the two measured diagonals
- Take multiple indentations across the specimen, respecting minimum spacing requirements between indentations to avoid work-hardening influence from adjacent tests
Low-Force and Microindentation Considerations
At very low forces (below 25 gf) or where the resulting indentation diagonal falls under roughly 25 microns, ASTM E384 (microindentation hardness) applies instead of E92, since surface preparation quality and optical measurement precision become disproportionately influential at that scale.
Applications
- Case-depth profiling: measuring hardness at incremental depths below a case-hardened surface to verify heat treatment penetration
- Weld and heat-affected zone (HAZ) characterisation: mapping hardness variation across a weld cross-section
- Thin coating and plated layer hardness: where the small indentation size allows testing without penetrating through to the substrate
- Quality control across the full hardness spectrum, from soft non-ferrous metals to hardened tool steel
Industry Specifications Referencing Vickers Hardness Testing
- ASTM E92: standard force-range Vickers and Knoop hardness testing
- ASTM E384: microindentation hardness testing
- ASTM E140: hardness conversion tables relating Vickers to Brinell, Rockwell, and approximate tensile strength
- ISO 6507: international equivalent Vickers hardness standard
Also Read – Polymer Hardness Testing: Common Uses, Methods & Scale Selection
Conclusion
Vickers testing earns its place in metallurgical labs precisely because one indenter geometry spans the full hardness range and works on small, thin, or precisely located features like weld HAZs and case-hardened layers — capabilities that come at the cost of a slower, more surface-preparation-sensitive test than Rockwell.
How is the Vickers hardness test performed? The specimen is positioned on a stable support, and a selected force is applied through the diamond indenter for a specified dwell time. The indentation is then viewed using an optical measuring system. Both diagonals are measured, their average is calculated, and the applied force and average diagonal length are used to determine hardness.
What does ASTM E384 cover? ASTM E384 covers microindentation hardness testing using Vickers and Knoop indenters. It addresses specimen preparation, test procedures, indentation measurement, result calculation, equipment verification, and factors affecting accuracy and repeatability. ASTM currently lists ASTM E384-22 as the active edition of the microindentation hardness standard.
What materials can be tested using the Vickers method? Vickers testing can be applied to metals, alloys, ceramics, coatings, welds, surface treatments, and other sufficiently solid materials. It is especially useful for evaluating small components, thin sections, individual microstructural phases, heat-affected zones, and hardness gradients that cannot be adequately measured using larger Rockwell or Brinell indentations.
Why must the specimen surface be polished? A smooth, flat, and properly polished surface is needed so that the indentation corners and diagonal boundaries can be clearly identified. Roughness, scratches, curvature, or poor mounting can distort the impression and cause measurement errors. Microindentation testing is particularly sensitive to specimen preparation because the indentation may be extremely small.
How is a Vickers hardness result reported? A Vickers result is reported using the hardness value, the symbol HV, and the applied test force. For example, 650 HV 0.5 indicates a Vickers hardness value of 650 obtained using a force of 0.5 kgf. A dwell time may also be included when it differs from the standard time specified by the applicable procedure.
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