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
Metal and Metallurgy Testing — 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.
Metal and metallurgical testing determines the load a metal or a welded joint can carry, how it fails and what its internal structure looks like. The output of this family is often not about the product itself but about the identity of the MATERIAL: is the steel really of the declared grade, does the weld seam deliver the strength the design assumes, does the casting contain an unacceptable internal defect?
The practical importance of the field comes from the fact that a metal part rarely fails gradually. A plastic part deforms, ages, cracks and usually gives warning. A weld seam or a fastener, by contrast, often breaks without warning — especially where fatigue and brittle fracture are involved. That is why in fields such as pressure equipment, lifting gear, structural steel and pipelines, material testing is a requirement of REGULATION rather than of design.
The family brings together three groups of methods, and each answers a different question. Mechanical tests quantify how the material behaves under load. Non-destructive examination looks for defects without damaging the part. Metallography and chemical analysis explain why the material behaves the way it does — through grain structure, phase distribution, inclusion content and alloy composition.
The acceptance criterion for these tests almost never comes from the test standard, and this is the key to understanding the field. The test standard says how the measurement is to be made; the acceptable values come from the product standard, the material grade or the fabrication code. ISO 6892-1 tells you how to run a tensile test; EN 10025 tells you what yield strength that steel must deliver. When reading a report, the product standard it was assessed against is essential.
Sampling is an inseparable part of the result in this field. Two specimens taken from the same heat may give different values depending on the direction and location they were taken from; in rolled products, specimens parallel and perpendicular to the rolling direction produce different results. Product standards therefore also govern sampling location and orientation, and the report must document this.
Method groups in this field
Mechanical tests
Tensile, compression, bending, notch impact (Charpy), hardness (Brinell, Vickers, Rockwell), fatigue, creep and fracture toughness. These give the behaviour of the material under load in numerical form.
Non-destructive examination
Radiography, ultrasonic examination, penetrant, magnetic particle and visual examination. It looks for surface and internal defects without damaging the part and is an indispensable step in welded fabrication.
Metallography
Specimen preparation, etching and microscopic examination. Grain size, phase distribution, inclusion content, case depth and the weld heat-affected zone are assessed.
Chemical analysis
Alloy composition is verified by optical emission spectrometry and wet chemistry; confirmation of the material grade runs through this step.
Corrosion behaviour
Salt spray, pitting and crevice corrosion and intergranular corrosion tests. In stainless steels these can indicate the quality of the heat treatment.
Commonly confused in this field
- A material certificate (such as EN 10204 3.1) is not a test report; it is the manufacturer's declaration. In critical applications independent verification is carried out, and the two must not be confused.
- ASTM and ISO tensile tests measure the same quantities but use different specimen geometries; the results are not treated as directly equivalent, and whichever the specification calls for is the one applied.
- Conversion tables between hardness and strength are APPROXIMATE. Calculating yield strength from hardness is not sufficient evidence for material acceptance.
- In non-destructive examination, "no defect found" does not mean there is no defect; defects below the detection limit of the method may be present. The report must state the method applied and the sensitivity level.
- A weld seam passing does not show that the welder or the procedure is qualified; these are separate processes.
Which decisions these results support
- Verifying the material certificate and accepting incoming material
- Approving welded fabrication; welder and procedure qualification
- Manufacturing control of pressure equipment and structural components
- Failure analysis and determining the root cause of field damage
- 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).