What Is Microhardness?
The microhardness test is a hardness measurement generally performed with a Vickers or Knoop indenter at loads below 1 kgf. It enables measurement of individual phases, thin layers and hardness gradients.
Purpose of Microhardness
The purpose is to determine case-hardening and nitriding depth, measure coating hardness, and map the hardness distribution in weld zones.
Which Products Is Microhardness Applied To?
- Surface-hardened parts
- Kaplamalar
- Weld and heat-affected zone
- Microstructural phases
- Small precision components
In Which Sectors Is Microhardness Used?
Standards Related to Microhardness
- ISO 6507-1
- ASTM E384
- ISO 4516
- ISO 2639
Microhardness Conditions
- Load
- Typically 10 gf – 1 kgf; chosen according to the application
- Indenter
- Vickers or Knoop
- Indentation spacing
- The distance between indentations must not fall below the minimum value defined in the standard
- Surface
- Metallographic polishing is mandatory
Equipment for Microhardness
- Microhardness machine
- Automatic stage and indentation-recognition system
- Specimen-preparation line
- Reference blocks
Sample Requirements for Microhardness
- A cross-section must be taken and mounted
- A deformation layer must not be created during polishing
- A measurement line from the surface inward must be planned for the hardness profile
Duration of Microhardness
The measurements are short; together with specimen preparation and profile measurement, a specimen typically takes half a working day.
Microhardness Procedure
- 1A specimen section is taken, mounted and polished.
- 2The machine is verified with reference blocks.
- 3The load and indenter appropriate to the application are selected.
- 4Indentations are made at defined intervals from the surface inward.
- 5The diagonals of each indentation are measured and hardness is calculated.
- 6A hardness-versus-depth profile is plotted.
Microhardness Acceptance Criteria
The acceptance criterion is generally defined as the depth at which a specified hardness value is reached (e.g. case-hardening depth).
Evaluation of Results
The hardness-versus-depth curve is compared with the threshold value in the specification. Indentations too close to each other are invalid.
Microhardness Report
- Standard applied
- Load, indenter and indentation spacing
- Measurement locations and depths
- Hardness values and profile graph
- Calculated hardening depth
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Heat-treatment and surface-treatment specifications
Mekanik Testler — What Does This Testing Field Cover?
The section below describes the field that the Microhardness test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Mechanical testing measures how a material or a part behaves under force. The family ranges from static loading (tension, compression, bending) to time-dependent behaviour (fatigue, creep), and from hardness and wear to fracture toughness.
What these tests have in common is that the result is reported as a MATERIAL PROPERTY. Yield strength or hardness is not a conformity decision; it is numerical data against which the design and the product standard will compare. Mechanical test reports are therefore usually an input to an engineering decision rather than to a product approval — material selection, safety factor, life prediction.
The distinction between static and dynamic behaviour is the key to understanding the field. A part may appear entirely unstressed under a static load yet break under repeated loading; fatigue fracture occurs at stresses well below the yield strength and gives no warning. For rotating, vibrating or cyclically loaded parts, a tensile test alone is therefore not sufficient evidence.
Test conditions determine the result, and this is critical for the readability of the report: specimen geometry, loading rate, temperature, conditioning and the gripping arrangement. The same material gives different values under different conditions. In plastics the rate effect is very pronounced, in metals the temperature effect; in composites the specimen orientation changes the result entirely.
Hardness is the most misused measurement in the field. Because it is fast, close to non-destructive and inexpensive, it is often used in place of strength. Conversion tables from hardness to strength exist, but they are APPROXIMATE and depend on the material group; using them as the sole evidence in material acceptance is wrong.
The fracture mechanics side requires a specific competence. Fracture toughness and fatigue crack growth rate measurements make it possible to calculate how long a cracked structure will last; they are the basis of damage-tolerant design in fields such as pressure equipment, aircraft structures and pipelines.
Method groups in this field
Static tests
Tension, compression, bending, shear and torsion. Yield and tensile strength, elongation and modulus of elasticity are obtained.
Impact tests
Charpy and Izod notch impact; the brittle-to-ductile transition behaviour of the material is determined as a function of temperature.
Hardness
Brinell, Vickers, Rockwell, Shore and micro hardness. Valuable for surface treatment depth and local differences in strength.
Fatigue
Force- and strain-controlled axial fatigue, fatigue in bending; S-N curves and the endurance limit.
Creep and stress relaxation
Behaviour under long-term load at high temperature; decisive for boiler, turbine and pressure equipment materials.
Fracture mechanics
Plane-strain fracture toughness, the J integral, CTOD and fatigue crack growth rate.
Wear and friction
Taber and rotating drum abrasion, coefficient of friction measurements.
Commonly confused in this field
- Calculating strength from hardness is approximate; it cannot be used as the sole evidence in material acceptance.
- Adequate static strength does not demonstrate fatigue strength; a cyclically loaded part requires a separate test.
- If test rate and temperature are not reported, the result cannot be compared — especially for polymers and composites.
- A test specimen and the actual part may not give the same value; moulding orientation, weld lines and differences in surface treatment all have an effect.
- A strength value given for a composite without stating the specimen orientation is meaningless.
- ASTM and ISO counterparts measure the same quantity but use different specimen geometries; the results are not treated as directly equivalent.
Which decisions these results support
- Design verification and material selection
- Incoming material control and supplier approval
- Meeting the mechanical requirements of the product standard
- Failure analysis, life prediction and damage tolerance calculation
- Verifying heat treatment and surface treatment processes
Related Tests
Frequently Asked Questions About Microhardness
According to which standard is Microhardness made?
Microhardness is executed in scope ISO 6507-1, ASTM E384, ISO 4516 and ISO 2639. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Microhardness apply to?
Mainly applied to Surface-hardened parts, Kaplamalar, Weld and heat-affected zone, Microstructural phases and Small precision components. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Microhardness done?
The determining parameters are: Load — Typically 10 gf – 1 kgf; chosen according to the application, Indenter — Vickers or Knoop and Indentation spacing — The distance between indentations must not fall below the minimum value defined in the standard. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Microhardness?
A cross-section must be taken and mounted, A deformation layer must not be created during polishing and A measurement line from the surface inward must be planned for the hardness profile. The number of samples is determined according to the product standard and the scope to be reported.
How long does Microhardness take?
The measurements are short; together with specimen preparation and profile measurement, a specimen typically takes half a working day. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Microhardness result called "appropriate"?
The acceptance criterion is generally defined as the depth at which a specified hardness value is reached (e.g. case-hardening depth).