What Is the Vickers Hardness Test? Definition & Simple Explanation
Introduction to the Vickers Hardness Test
If you are new to materials testing and have encountered the term “Vickers hardness test,” this guide explains everything you need to know — what it measures, how it works, what the results mean, and where it is used in industry. The Vickers hardness test is one of the most important and versatile mechanical tests performed on metals, ceramics, and coatings, appearing in virtually every metals and materials testing laboratory worldwide.
What Does the Vickers Test Measure?
The Vickers test measures hardness — the resistance of a material to localised permanent deformation (indentation) by a harder body. A harder material leaves a smaller indentation under the same load; a softer material leaves a larger indentation. The Vickers Hardness Number (HV) is inversely proportional to the indentation size — harder materials have higher HV values.
Hardness is not a single fundamental property but correlates with many important material behaviours:
- Higher HV generally corresponds to higher tensile strength (for steels: UTS ≈ 3.3 × HV in MPa)
- Higher HV indicates better wear resistance
- Higher HV in heat-treated components indicates correct heat treatment
How the Vickers Test Works: Step by Step
The Indenter
The Vickers indenter is a four-sided (square base) diamond pyramid with face angles of exactly 136°. This specific angle was chosen because it is close to the ideal angle for hardness testing where the impression is geometrically similar regardless of size — meaning the HV number is independent of the applied load (a unique feature of the Vickers test).
The Test Procedure
- The specimen surface is prepared by grinding and polishing to a flat, reflective surface
- The diamond pyramid indenter is pressed into the surface under the selected test force for 10–15 seconds
- After the load is removed, the square pyramid residual indentation remains in the surface
- The two diagonals of the square indentation are measured using a calibrated optical microscope
- The mean diagonal d = (d₁ + d₂)/2 is calculated
- Vickers hardness is calculated: HV = 1.8544 × F / d² (F in kgf, d in mm)
Example Calculation
If F = 1 kgf and d = 0.1 mm: HV = 1.8544 × 1 / (0.1)² = 1.8544 / 0.01 = 185 HV
This means the material has a Vickers hardness of 185 — soft to medium hardness, typical of annealed carbon steel.
Understanding Vickers Hardness Numbers
The HV scale runs from approximately:
- 10–50 HV: Very soft metals (lead, pure aluminium, copper)
- 50–150 HV: Soft to medium steels, brass, bronze, annealed alloys
- 150–300 HV: Medium to hard steels, cold-worked metals
- 300–600 HV: Hardened steels, tool steels, case-hardened surfaces
- 600–1000+ HV: Carbide coatings, ceramics, diamond-like carbon coatings
- ~10,000 HV: Diamond (the hardest natural material)
Vickers Load Notation and Scale
The test force used must always be reported alongside the HV number:
- 800 HV 30 = 800 Vickers hardness measured with 30 kgf load
- 550 HV 1 = 550 HV at 1 kgf load
- 200 HV 0.3 = 200 HV at 300 gf load (microhardness)
Because the Vickers test is geometrically similar across all loads, the HV number is independent of load for a homogeneous material — but load selection matters for testing thin layers, coatings, or small features.
When Is the Vickers Test Used?
The Vickers test is preferred over Rockwell and Brinell in several situations:
- Testing coatings and thin sections (micro loads, small indentation)
- Case depth profiling — measuring hardness variation from surface to core in carburised or nitrided components
- Weld inspection — measuring hardness variation across base metal, HAZ, and weld metal
- Research — comparing hardness of individual phases in multiphase materials
- Hard materials — ceramics, carbides, and coatings too hard for ball indenters
Industrial Applications
Every day, millions of Vickers hardness measurements are made in aerospace heat treatment quality control, automotive gear and bearing inspection, semiconductor wafer process monitoring, tool steel production, and medical implant surface characterisation.
Why Choose Infinita Lab for Vickers Hardness Testing?
Infinita Lab provides Vickers hardness testing at all loads — from 1 gf to 50 kgf — through our nationwide accredited mechanical testing laboratory network, with automated and manual instruments for any testing requirement.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.
Frequently Asked Questions (FAQs)
What is the difference between Vickers and Rockwell hardness tests? Rockwell measures indentation depth directly and reads hardness instantly on a dial — fast, convenient, but limited in scale range. Vickers measures the diagonal of a pyramid indentation optically — slower (requires measuring the indent), but provides a single universal scale covering all materials, smaller indentation for thin sections, and better spatial resolution for microstructure mapping.
Why is the 136° face angle special for the Vickers indenter? The 136° face angle produces geometrically similar indentations — the ratio of indentation depth to diagonal length is the same regardless of indentation size. This geometric similarity means the HV number is independent of load level, unlike Brinell hardness which changes with load due to geometrical dissimilarity at different loads.
What surface finish is required for Vickers hardness testing? For macrohardness testing (1 kgf and above), a smooth, flat ground or polished surface is sufficient. For microhardness testing (below 1 kgf), the surface must be metallographically polished to 1 µm diamond or finer — because at very small indentation sizes, surface roughness becomes comparable to the indent diagonal and causes measurement errors.
How many indentations are typically made for a reliable average hardness value? For bulk material hardness, three to five indentations are typically made in different locations on the specimen and averaged. For case depth profiling, individual measurements are made at each specified position from the surface into the core — typically at 0.1–0.5 mm spacing depending on the case depth and required resolution.
Can Vickers hardness be converted to tensile strength? For carbon and low-alloy steels in the 150–650 HV range, an approximate empirical relationship applies: UTS (MPa) ≈ 3.3 × HV. This conversion is material-specific and less reliable for stainless steels, aluminium alloys, and non-metals. ASTM E140 provides conversion tables, with notes on the limitations for specific alloy systems.
