microhardness Testing Services: Precision Characterisation for Thin Sections, Coatings & Small Components

As an independent third-party testing service provider, we offer comprehensive microhardness testing for materials and components where conventional macro‑hardness methods (Rockwell, Brinell, macro Vickers) are impractical or invalid. microhardness testing uses very low test forces – typically from 1 gf (0.0098 N) to 1000 gf (9.807 N) – to produce microscopic indentations that are measured with high‑magnification optical systems. The two most common microhardness methods are Vickers microhardness (HV) and Knoop microhardness (HK). These methods are essential for evaluating thin coatings, case‑hardened layers, electroplated films, small precision components, individual microstructural phases (e.g., martensite, ferrite, carbides), brittle ceramics, glass, semiconductors, and welded heat‑affected zones (HAZ). Our accredited laboratory follows international standards (ISO 6507, ASTM E384, ISO 4545) to deliver accurate, reproducible, and legally defensible microhardness data. This article outlines our microhardness testing capabilities – including scope, key test items, load selection, sample preparation, and standard methods – to help manufacturers, heat treaters, coating specialists, quality assurance teams, and research laboratories obtain reliable hardness characterisation at the micro‑scale.

1. What Is microhardness Testing?

microhardness testing is a family of indentation hardness methods that use very low test forces (≤ 1 kgf / 9.807 N) to produce indents typically measuring 10‑100 μm in diagonal length. Because the indents are microscopic, the specimen must be prepared with a highly polished flat surface, and the indentation is measured under an optical microscope (magnification 400× to 1000×). microhardness testing is not merely “small” hardness testing – it serves distinct purposes:

Thin sections & small components – Parts that are too thin or small for macro indentation can be evaluated without substrate influence (provided the indentation depth is ≤ 1/10 of the thickness).
Surface layers & coatings – Case‑hardened layers (carburised, nitrided), PVD/CVD coatings, electroplated layers (Ni, Cr, Au), anodised layers, and thermal spray coatings.
Individual microstructural phases – Hardness of specific phases (e.g., carbides in tool steel, intermetallic compounds, ceramic inclusions) can be measured by targeting the indenter precisely under microscopic observation.
Brittle materials – Ceramics, glass, and semiconductors can be tested without causing excessive cracking, especially using the Knoop method which has a shallower penetration depth.
Hardness gradients – microhardness traverses across weld HAZ, from surface inward for case depth profiling, or across diffusion zones.

The two dominant methods are:

Vickers microhardness (HV) – Uses a diamond square‑based pyramid indenter (136° included angle). Both diagonals of the square indentation are measured and averaged. Vickers microhardness is load‑independent for homogeneous materials and provides a continuous scale from soft (< 50 HV) to extremely hard (> 2000 HV). Expression: e.g., 750 HV0.3 means 750 HV measured with a test force of 0.3 kgf (300 gf).

Knoop microhardness (HK) – Uses an elongated rhombic‑based diamond indenter (172.5° and 130° included angles). Only the long diagonal is measured. The Knoop indentation is approximately 1/30 of the long diagonal in depth – much shallower than Vickers (depth ≈ 1/7 of diagonal). This makes Knoop ideal for very thin coatings and surface layers, or for minimising cracking in brittle materials. Expression: e.g., 520 HK0.1 means 520 HK with a test force of 0.1 kgf (100 gf).

2. Our Testing Scope for microhardness

We cover a wide range of materials, test loads, sample geometries, and specialised applications:

By material type: Case‑hardened steels (carburised, carbonitrided, nitrided, induction‑hardened, flame‑hardened) – case depth profiling and surface hardness; Tool steels (D2, M2, H13) – hardness of carbides and matrix; stainless steels – austenitic, martensitic, precipitation‑hardening; Non‑ferrous metals (aluminium, copper, titanium, nickel superalloys) – fine‑grained or thin sections; Coatings – PVD (TiN, TiAlN, CrN, AlCrN, DLC), CVD (diamond, TiC), electroplated (Ni, Cr, Au, Ag, Zn), thermal spray (WC‑Co, Cr₂C₃‑NiCr), anodised aluminium oxide; Ceramics and hardmetals – alumina, zirconia, silicon carbide, silicon nitride, tungsten carbide‑cobalt (WC‑Co), cermets; Glass – float glass, borosilicate, quartz, optical glass, glass ceramics; Semiconductors – silicon wafers (monocrystalline and polycrystalline), GaAs, SiC; Sintered materials – powder metallurgy parts, metal‑injection moulded (MIM) components; Welded sections – weld metal, heat‑affected zone (HAZ), dissimilar metal welds; Plastics and composites (limited to harder engineering plastics).

By test force range: Micro Vickers (HV) – 1 gf to 1000 gf (0.0098 N – 9.807 N), covering HV0.001 through HV1; Knoop (HK) – 1 gf to 1000 gf (HK0.001 – HK1). We also offer extended low‑force testing down to 0.5 gf (HV0.0005) for ultra‑thin coatings (by arrangement).

By specimen configuration: Flat polished cross‑sections (mounted in resin or Bakelite) – for case depth profiling and coating cross‑section evaluation; Unmounted parts – small components, sheets, foils; Curved or irregular surfaces – requires careful levelling; Thin films and coatings on substrates – requires proper load selection to avoid substrate influence.

By test environment: Laboratory (controlled temperature 23±2°C, vibration‑isolated base); Special environments (elevated/low temperature by arrangement).

3. International Standards & Compliance

All microhardness tests are performed in strict accordance with the following international standards:

ASTM E384 (Standard test method for microindentation hardness of materials) – Primary US standard covering Vickers and Knoop microhardness testing with loads from 1 gf to 1000 gf. Defines test procedures, verification, calibration, specimen preparation, measurement criteria (minimum diagonal length 20 μm), indentation spacing, and reporting.
ISO 6507‑1 (Metallic materials – vickers hardness test – Part 1: Test method) – International standard for vickers hardness, including macro (≥ 5 kgf) and micro (< 5 kgf) ranges. For micro loads, special provisions for surface finish and measurement.
ISO 4545‑1 (Metallic materials – knoop hardness test – Part 1: Test method) – International standard for Knoop microhardness testing, covering 1 gf to 2 kgf.
GB/T 4340.1 (Metallic materials – vickers hardness test – Part 1: Test method) – Chinese national standard.
GB/T 18449.1 (Metallic materials – knoop hardness test – Part 1: Test method).
ISO 6507‑2 (Verification and calibration of testing machines).
ISO 4545‑2 (Knoop – verification and calibration).
ISO 6507‑3 (Calibration of reference blocks).
ISO 4545‑3 (Knoop reference blocks).

4. Key Test Items & Measurement Parameters

Our microhardness testing services produce detailed, high‑precision data for a variety of applications. Key parameters and deliverables include:

Vickers microhardness (HV) – Direct measurement using a calibrated microhardness tester. The test force is selected based on specimen thickness or layer depth. For each indentation, both diagonals (d₁, d₂) are measured via optical microscope or automated image analysis. The average diagonal length d = (d₁ + d₂) / 2 is used to calculate HV = 1.8544 × F / d² (F in kgf, d in mm). The result is expressed as, for example, 620 HV0.3 (620 HV with 300 gf load).

Knoop microhardness (HK) – Similar procedure, but only the long diagonal (d) is measured. The formula for HK = 14.229 × F / d² (F in N, d in mm) or HK = 1.451 × F / d² (F in kgf, d in mm). The shallow indentation depth makes Knoop the preferred method for thin coatings (< 20 μm).

Test force (load) selection – For bulk homogeneous materials, a higher load (e.g., 500 gf or 1000 gf) is preferred to minimise scatter from microstructural inhomogeneities. For case‑hardened layers, the load is selected so that the indentation depth is less than 1/10 of the case depth to avoid substrate softening effects. For a carburised layer of 0.3 mm effective depth, a 300 gf (HV0.3) or 500 gf (HV0.5) load is typical. For a thin PVD coating of 3 μm thickness, a 10‑25 gf load is used, and the Knoop indenter is often preferred.

Case depth profiling (microhardness traverse) – A series of Vickers or Knoop indentations are made at increasing distances from the surface, typically at intervals of 0.05 mm, 0.10 mm, or 0.20 mm, depending on case depth and standard. The hardness vs. distance curve is plotted, and the effective case depth (DC) is defined as the distance from the surface where the hardness falls to a specified threshold (e.g., 550 HV for carburised steel per ISO 2639, GB/T 9450). We provide both tabular data and graphical profiles.

Coating‑only hardness – For coatings on a softer substrate, we select a test load such that the indentation depth does not exceed 10% of the coating thickness. This ensures minimal substrate influence. For very thin coatings (< 5 μm), the Knoop indenter is preferred due to its shallow penetration.

Phase‑specific microhardness – Under high magnification (500× to 1000×), we can aim the indenter at individual microstructural features (e.g., primary carbides in tool steel, intermetallic particles in superalloys, or ferrite/martensite phases). This is essential for failure analysis and material development.

microhardness uniformity mapping – For heat‑treated components or welded joints, we perform a grid of indentations to create a 2D hardness map, highlighting soft or hard zones.

Conversion to other scales – We provide approximate conversions to HRC, HRB, HB, and tensile strength (for steels) using ASTM E140 conversion tables, with a disclaimer that micro‑load results may differ from macro‑converted values.

5. Test Procedure & Specifications

Our laboratory strictly adheres to the requirements of ASTM E384, ISO 6507‑1, and ISO 4545‑1. The key steps and specifications are summarised below:

Specimen preparation – The test surface must be flat, highly polished, and free from scratches, embedded abrasives, burns, or residual stress layers. For microhardness, the required surface finish is Ra ≤ 0.1 μm (mirror finish). Specimens are typically mounted in epoxy or acrylic resin (for cross‑sections) or directly clamped for flat parts. Polishing is performed sequentially with diamond pastes (6 μm, 3 μm, 1 μm) and final polishing with colloidal silica (0.05 μm). Etching may be applied after hardness testing to reveal microstructure, but hardness must be measured on the unetched surface to avoid measurement errors from differential etching.

Indentation procedure – The specimen is placed on a rigid anvil and levelled. The test force is applied smoothly without impact. The loading rate is controlled (typically 20‑50 μm/s). The specified dwell time is maintained (standard 10‑15 seconds for metals; 30‑60 seconds for polymers, ceramics, or soft materials). After dwell, the force is removed, and the indentation is measured.

Indentation measurement – Using an optical microscope with calibrated objective lenses (400× to 1000×). The measurement resolution must be ≤ 0.5 μm. For Vickers, both diagonals are measured; if the difference between diagonals exceeds 5% of the smaller diagonal, the indentation is rejected. For Knoop, the long diagonal is measured. The mean diagonal length is used for hardness calculation. For each test condition, a minimum of 5 valid indentations are made and averaged.

Indentation spacing – Distance between indentation centres must be at least 2.5 times the diagonal length for Vickers (or 3 times for Knoop). Distance from any indentation to the specimen edge must be ≥ 2.5 times the diagonal length.

Verification and calibration – The microhardness tester is verified daily using certified reference blocks (calibrated to ISO 6507‑3 or ISO 4545‑3) at two hardness levels covering the expected range. At least 5 indentations are made on the reference block; the average HV/HK must be within the certified tolerance (±5% for micro ranges). The measuring system (microscope) is calibrated using a stage micrometer. Annual direct verification by an accredited laboratory verifies test force accuracy (±1.0% for loads ≥ 100 gf, ±1.5% for lower loads), indenter geometry, dwell timer, and measurement system.

6. Typical Applications & Suitable Specimens

microhardness testing is essential for the following applications where macro‑hardness is not feasible:

Case‑hardened components – Gears, shafts, bearings, camshafts that have been carburised, carbonitrided, or nitrided. Hardness profiles from the surface inward determine effective case depth per ISO 2639, GB/T 9450, or QC/T 262. Typical loads: HV0.3 to HV1.

Thin coatings – PVD/CVD coatings (TiN, TiAlN, CrN, DLC, AlTiN) for cutting tools; electroplated nickel, chromium, gold, silver; anodised layers on aluminium; thermal spray coatings (WC‑Co, Cr₂C₃). Knoop microhardness with loads of 10‑100 gf is preferred for coating thicknesses below 20 μm.

Semiconductors – Silicon wafers (hardness mapping, subsurface damage assessment), GaAs, SiC substrates. microhardness helps optimise polishing and dicing processes. Typical loads: HV0.01 to HV0.1.

Ceramics and glass – Advanced ceramics (alumina, zirconia, SiC), optical glasses, glass ceramics. Knoop microhardness is often used because its shallow indentation reduces cracking. Loads: 100‑500 gf.

Small precision components – Watch parts, medical implants (dental crowns, hip balls), miniature gears, fine springs. The small indentation (typically < 50 μm diagonal) does not damage the component.

Welded joints – microhardness traverses across the weld metal, HAZ, and base metal reveal softening or hardening due to thermal cycles – critical for welding procedure qualification (e.g., ISO 15614, AWS D1.1).

Heat‑affected zones (HAZ) – After laser, electron beam, or induction hardening, microhardness mapping ensures uniform hardness depth.

Research and failure analysis – Characterisation of individual phases (carbides, intermetallics), residual cold work evaluation, and assessment of decarburisation or embrittlement.

7. Advantages & Limitations of microhardness Testing

Understanding the strengths and limitations helps ensure proper application and interpretation.

Advantages: Enables hardness testing of small, thin, or surface‑treated components that cannot be tested by macro methods. High spatial resolution allows mapping of hardness gradients (case depth, HAZ, diffusion zones). Very low test forces allow testing of individual microstructural phases. Vickers microhardness provides a continuous scale across all materials, from soft to extremely hard. Knoop microhardness offers extremely shallow penetration for ultra‑thin coatings. The small indentations are often non‑destructive for finished parts. Good correlation with other mechanical properties (tensile strength, wear resistance) for homogeneous materials.

Limitations: Requires meticulous sample preparation (mirror finish) and skilled operator to achieve repeatable results. Measurement is slower than Rockwell or Leeb (minutes per indentation). Results are sensitive to surface finish; rough or damaged surfaces produce invalid data. For heterogeneous materials (e.g., cast irons), several indentations must be averaged to obtain representative values. Low load (≤ 50 gf) results may have higher uncertainty due to grain boundary effects and tip bluntness. The test is not suitable for very soft materials (< 20 HV) or very hard materials (> 2500 HV). Conversions to macro hardness scales (HRC, HB) have limited accuracy, especially for thin coatings or case‑hardened layers.

8. Reporting & Result Presentation

Our test reports are detailed, transparent, and compliant with ISO/IEC 17025, ASTM E384, ISO 6507, and ISO 4545. Each report includes:

Specimen identification – Material grade, heat number, component description, sampling location, orientation, and preparation method (mounted, polished, etched).
Test conditions – Standard referenced, microhardness method (Vickers or Knoop), test force (e.g., 300 gf), dwell time, temperature, indenter type (diamond pyramid – Vickers or Knoop).
Individual indentation data – For each indentation: measured diagonal lengths (d₁, d₂ for Vickers, or long diagonal d for Knoop), calculated HV or HK, and remarks (e.g., “targeted carbide”).
Statistical summary – Mean HV/HK, standard deviation, coefficient of variation, range, and number of indentations.
Case depth profile (if applicable) – A table of hardness vs. distance from surface (mm) and a graph of HV/HK vs. depth. The effective case depth (mm) is reported according to the specified threshold (e.g., 550 HV).
Metallographic images – High‑resolution images of selected indentations (showing the measurement lines) and, if requested, microstructural images of the area.
Equipment calibration status – Tester model and serial number, date of last calibration, reference block certified values, verification results, measurement system calibration.
Compliance statement – Pass/fail determination against customer specification, standard requirement, or purchase order.
Remarks – Any deviations from standard (e.g., use of Knoop for thin coating, stacked specimens).

9. Why Choose Our Third‑Party microhardness Testing Services?

As an independent laboratory with specialised expertise in micro‑indentation, we provide unbiased, accurate, and legally defensible microhardness data. Our advantages include:

ISO/IEC 17025 accreditation – Our microhardness testing (Vickers and Knoop) is CNAS and CMA accredited, with regular participation in proficiency testing (e.g., ASTM E384 round robins).
Precision microhardness testers – We operate fully automated microhardness testers (Wilson Tukon 2500, Mitutoyo HM‑220, Shimadzu HMV‑G21) with test force range 0.5 gf to 2000 gf, closed‑loop load cell control, motorised XY stages (for automated traverses), and high‑resolution digital cameras with image analysis software (automated diagonal measurement).
Dual indenter capability – All testers can be fitted with both Vickers (square pyramid) and Knoop (rhombic pyramid) indenters, allowing us to select the optimal method for your application.
Case depth profiling – Our automated traverses can run up to 100 indentations with programmable spacing (e.g., 0.05 mm, 0.1 mm) along a straight line, and the system automatically measures each indentation and generates the hardness profile graph.
Thin coating expertise – For coatings thinner than 20 μm, we use Knoop microhardness with loads as low as 10 gf, ensuring that the indentation depth remains within the coating layer. We also offer coating‑only hardness measurements with substrate influence analysis.
Fast turnaround – Routine microhardness testing (5‑10 indentations on a polished sample) typically completed within 2‑3 business days. Automated case depth profiles (50‑100 indentations) in 3‑5 business days.
Detailed reporting – Reports include indentation images, statistical summaries, calibration certificates, and clear pass/fail conclusions.
Confidentiality – Full protection of your material, coating, and component information.
Consultative support – Our materials scientists help select the appropriate method (Vickers vs. Knoop), test load, and indentation spacing; interpret case depth profiles; and advise on sample preparation for difficult materials (e.g., extremely brittle, soft, or thin).

Whether you need to measure the case depth of a carburised gear, evaluate the hardness of a PVD coating on a cutting tool, characterise individual phases in a superalloy, or perform a hardness traverse across a welded HAZ, our microhardness testing experts are ready to deliver precise, reliable, and actionable results.

Get Started with Your microhardness Testing Project

Contact our team with your material type, required method (Vickers or Knoop), estimated hardness range, expected case depth or coating thickness (if applicable), specimen dimensions, and applicable standard (ASTM E384, ISO 6507, ISO 4545, GB/T 4340, etc.). We will provide a detailed quotation, sample preparation guidelines (including mounting and polishing recommendations), and a testing schedule. Let us help you obtain high‑precision microhardness data for your most demanding applications.

This article provides an overview of our microhardness testing capabilities. For specific test methods, sample quantity, and pricing, please request a tailored service proposal.