Solid Hardness Testing Procedures: A Complete Step-by-Step Guide to Brinell, Rockwell, Vickers and S

Solid hardness testing is one of the most widely performed mechanical tests for evaluating a material's resistance to permanent indentation, scratching and plastic deformation. This step-by-step guide explains the complete solid hardness testing procedures for metallic and polymeric materials in accordance with ISO, ASTM, EN, GB and JIS standards, covering sample preparation, indenter selection, force application, indentation measurement and result reporting. Following the correct hardness test steps—whether in-house or through accredited third-party laboratories—ensures repeatable, comparable and traceable test results.

Technical Overview

Hardness testing quantifies the ability of a solid material to resist localized plastic deformation. In practice, an indenter of defined geometry—a hardened steel or carbide ball, a diamond cone, or a diamond pyramid—is pressed into the specimen surface under a controlled test force. The size or depth of the resulting permanent indentation is then measured and converted into a standardized hardness number. Because the test is fast, comparatively non-destructive at low loads, and directly correlated with strength and wear behavior, it is a cornerstone of incoming material inspection, heat-treatment qualification and failure analysis.

The principal standardized methods covered in this article include the Brinell test (ISO 6506, ASTM E10, GB/T 231.1, JIS Z 2243), the Rockwell test (ISO 6508, ASTM E18, GB/T 230.1, JIS Z 2245), the Vickers test (ISO 6507, ASTM E92, GB/T 4340.1, JIS Z 2244), microindentation testing (ASTM E384), instrumented indentation (ISO 14577) and Shore durometer testing for polymers (ISO 868, ASTM D2240, GB/T 531.1). Although the scales differ, all of these procedures share a common sequence: specification review, specimen preparation, machine verification, indentation, measurement, calculation and reporting.

• Brinell (HBW): large ball indenter, ideal for coarse-grained and inhomogeneous materials such as castings and forgings.
• Rockwell (HRA/HRB/HRC and superficial scales): depth-based reading, fast and well suited to production control.
• Vickers (HV): diamond pyramid applicable across a very wide hardness range, from soft aluminum to hardened tool steel and ceramics.
• Micro-Vickers and Knoop (HV0.01–HV1, HK): low-force indentation for coatings, weld microstructures and case-depth traverses.
• Shore (Shore A, Shore D): durometer method for elastomers and plastics.

Testing Samples

Metallic Raw Materials and Semi-Finished Products

Typical specimens include plates, sheets, bars, rods, tubes, forgings and castings made of carbon steel, alloy steel, stainless steel, cast iron, aluminum alloys, copper alloys, titanium alloys and nickel-based superalloys. The surface to be tested must be representative of the bulk material, free of scale, oxide, decarburized layers, paint and lubricants.

Welded Joints and Heat-Affected Zones

Sectioned cross-sections of butt welds, fillet welds and clad joints are prepared by grinding and polishing so that hardness traverses can be taken across the weld metal, the fusion line and the heat-affected zone (HAZ) in accordance with weld qualification codes and ISO 9015-1 / ISO 22826 type procedures.

Heat-Treated and Surface-Hardened Components

Quenched-and-tempered parts, carburized or nitrided gears, induction-hardened shafts and shot-peened springs are tested to verify heat-treatment quality. Microhardness traverses are used to determine effective case depth (CHD) to the 550 HV1 criterion as defined in ISO 2639 or ASTM E384.

Machined Components and Fasteners

Bolts, nuts, studs, pins, bearings, valve seats and machined structural parts are hardness tested for conformance to product standards such as ISO 898-1 for threaded fasteners, where hardness correlates directly with the property class.

Polymers, Elastomers, Ceramics and Coatings

Rubber sheets, seals, plastic moldings, composites, engineering ceramics, sintered carbides, electroplated layers, thermal-spray coatings and anodized films are evaluated with Shore durometers, micro-Vickers or Knoop indenters depending on thickness and expected hardness.

Testing Items

The solid hardness test portfolio typically includes the following measurable items, each reported with its standardized scale designation:

• Brinell hardness (HBW) at forces from 9.807 N to 29420 N with 1 mm to 10 mm carbide ball indenters.
• Rockwell hardness: regular scales HRA, HRB, HRC, HRD, HRE and superficial scales HR15N, HR30T, HR45T and others.
• Vickers hardness: macro range HV5, HV10, HV30, HV50 and HV120.
• Micro-Vickers and Knoop hardness: HV0.01, HV0.025, HV0.05, HV0.1, HV0.3, HV0.5, HV1 and HK equivalents.
• Shore hardness of plastics and elastomers: Shore A, Shore D, Shore AO and Shore DO.
• Effective case depth (CHD), total case depth, nitriding depth (NHT) and hardenability (Jominy) traverses.
• Hardness uniformity surveys and hardness-value conversion between scales.
• High-temperature hardness and instrumented indentation (Martens hardness, HM) per ISO 14577 where required.

Testing Methods

Common Preparatory Steps for All Hardness Tests

Regardless of the selected scale, the solid hardness test procedure begins with the following universal steps, which are prerequisites for valid results under ISO, ASTM, EN and GB standards:

• Step 1 – Specification review: identify the governing standard, required scale, force level, dwell time and acceptance limits from the drawing, purchase order or material specification.
• Step 2 – Specimen preparation: grind or polish the test surface until it is smooth, flat and free of oxide, oil and decarburized material; for microhardness, polish to a metallographic finish, typically 1 μm or finer, and etch only after indentation where microstructure must be visible.
• Step 3 – Thickness check: confirm that the specimen is at least 8 to 10 times the expected indentation depth so that no bulging or marking appears on the reverse side.
• Step 4 – Environment control: perform the test at a stable ambient temperature, normally 10 °C to 35 °C, on a vibration-free bench.
• Step 5 – Machine verification: confirm that the tester is within its calibration interval and perform indirect verification using certified reference blocks in accordance with ISO 6506-2, ISO 6507-2, ISO 6508-3 or the corresponding ASTM verification documents.
• Step 6 – Mounting: seat the specimen on a rigid anvil, with the test surface perpendicular to the indenter axis and the area of interest correctly aligned.
• Step 7 – Indentation and measurement: apply the force without shock, hold for the specified dwell time, then measure the indentation or read the direct hardness value.
• Step 8 – Repetition and reporting: perform the required number of indentations, apply spacing rules, calculate the mean and issue a complete test report.

Brinell Hardness Test Procedure (ISO 6506-1 / ASTM E10 / GB/T 231.1)

• Step 1 – Select a tungsten carbide ball indenter, commonly 10 mm diameter (1 mm, 2.5 mm and 5 mm balls are also permitted), and choose the test force so that the force-to-ball-diameter-squared ratio (0.102·F/D²) suits the material: 30 for steels and titanium, 10 for copper alloys, 5 for brasses and bronzes, and 2.5 or 1 for soft aluminum alloys and bearing metals.
• Step 2 – Target an indentation diameter between 0.24 D and 0.6 D, which typically corresponds to a dwell time of 10 to 15 seconds for metallic materials.
• Step 3 – Apply the force smoothly, increasing to full load within 2 to 8 seconds, then hold for the selected dwell time.
• Step 4 – Remove the force and measure the indentation diameter d in two perpendicular directions using a calibrated microscope or automatic optical system; the average diameter is used for calculation.
• Step 5 – Calculate HBW = 0.102 × 2F / (πD(D − √(D² − d²))) or read the value from a standard lookup table, and report as, for example, 210 HBW 10/3000.
• Step 6 – Respect spacing limits: the center of any indentation must be at least 3d from another indentation center and 2.5d from the specimen edge.

Rockwell Hardness Test Procedure (ISO 6508-1 / ASTM E18 / GB/T 230.1)

• Step 1 – Select the scale according to material and expected hardness: HRC (diamond cone, 150 kgf total force) for hardened steels above approximately 20 HRC; HRB (1.588 mm ball, 100 kgf) for annealed steels and copper alloys; HRA for thin hard layers and carbides; superficial scales such as HR30T for thin sheet.
• Step 2 – Apply the preliminary force of 10 kgf (3 kgf for superficial scales) and allow the machine to establish the depth reference zero.
• Step 3 – Apply the additional test force within 1 to 8 seconds to reach the total force, then hold for a dwell of 2 to 6 seconds, with 3 to 4 seconds typical for HRC.
• Step 4 – Return to the preliminary force and read the hardness value directly from the digital display or dial, since the Rockwell number is derived from the permanent increase in penetration depth h (for HRC, HR = 100 − h/0.002 mm).
• Step 5 – Move the specimen so that successive indentations are spaced at least 4 indentation-diameters apart (3 for superficial scales) and at least 2.5 diameters from any edge.
• Step 6 – Record the scale designation, e.g., 45 HRC or 88 HRB, without unit conversion between scales.

Vickers Hardness Test Procedure (ISO 6507-1 / ASTM E92 / GB/T 4340.1)

• Step 1 – Select the test force; common production levels are HV10, HV30 and HV50, and the diamond right pyramid with a 136° face angle is used for the full range from very soft to very hard materials.
• Step 2 – Apply the force perpendicular to the surface, reaching full force without shock, and hold for 10 to 15 seconds.
• Step 3 – Measure both diagonals d1 and d2 of the square indentation with a microscope at calibrated magnification and compute the mean diagonal d.
• Step 4 – Calculate HV = 0.1891 × F/d² (F in newtons, d in millimetres) or read from tables; report as, for example, 620 HV10 or 620 HV10/15 where dwell differs from the standard.
• Step 5 – Maintain center-to-center spacing of at least 2.5 diagonal lengths (3 is recommended) and at least 2.5 diagonals from the edge; the specimen thickness must exceed 1.5 times the diagonal length.

Microhardness and Case Depth Testing Procedure (ASTM E384 / ISO 2639)

• Step 1 – Section the component perpendicular to the hardened surface, mount it and polish to a scratch-free metallographic finish, avoiding any heating or working that alters the surface layers.
• Step 2 – Select a low force, typically HV0.5 or HV1 for case-depth traverses and HV0.01 to HV0.1 for thin coatings, ensuring the indentation depth is no more than one tenth of the layer thickness.
• Step 3 – Perform a traverse: place a row of indentations at defined depth increments from the surface inward, with spacing of at least 2.5 diagonals between indentations.
• Step 4 – Plot hardness versus depth and determine the effective case depth (CHD) as the depth at which hardness equals 550 HV1 for carburized cases per ISO 2639; report nitriding hardness depth (NHT) at the core-hardness +50 HV criterion where applicable.
• Step 5 – For Knoop testing of brittle or thin coatings, apply the elongated diamond indenter and report HK with the test force and dwell time.

Shore Durometer Test Procedure for Polymers (ISO 868 / ASTM D2240)

• Step 1 – Condition the specimen at standard laboratory temperature and prepare a flat test area at least 6 mm thick; thinner materials may be stacked, provided the layers do not interpenetrate.
• Step 2 – Select the durometer type: Shore A for soft elastomers, Shore D for hard plastics and thermosets.
• Step 3 – Press the indenter firmly against the specimen with the presser foot parallel to the surface, keeping the specimen at least 9 mm from any edge and 6 mm from previous indentations.
• Step 4 – Read the maximum value within the standard timing—commonly the instantaneous reading or the 15-second reading as specified—and report with timing, e.g., Shore A 70/15s.
• Step 5 – Take at least five readings at different points and report the median or mean as required by the specification.

Result Calculation, Verification and Reporting

For each method, at least three valid indentations are normally required, and the individual values together with the arithmetic mean are reported. Where conversion between scales is unavoidable, recognized conversion tables such as ISO 18265 and ASTM E140 must be used, and the report must state that the values are converted and therefore approximate. A complete hardness test report identifies the test standard, method and scale, indenter and force, dwell time, number of indentations, individual and mean values, specimen identification and location, machine calibration status, laboratory temperature, and any anomalies such as edge effects, bulging or visible material defects. Testing performed by accredited third-party laboratories under ISO/IEC 17025 provides an added level of traceability for regulatory or contractual acceptance.

Applications

Solid hardness testing is applied across virtually every industry that processes or fabricates engineering materials, because hardness correlates closely with tensile strength, machinability, wear resistance and heat-treatment quality:

• Aerospace: verification of landing-gear steels, titanium forgings and nickel superalloy components against AMS and customer specifications.
• Automotive: incoming inspection of fasteners, gears, crankshafts, camshafts and case-hardened transmission parts, including weld and HAZ qualification.
• Oil and gas: hardness limitation of weldments and pipeline steels to control sulfide stress cracking risk in sour service (NACE MR0175 / ISO 15156 type requirements).
• Construction and structural steel: confirmation of steel grades, bolts and welds for EN 1090 and GB 50205 conformity programs.
• Power generation and pressure equipment: hardness surveys of boiler tubes, pressure-vessel welds and repaired components under ASME-type and EN 13445-type regimes.
• Medical devices: microhardness verification of surgical implants, cutting instruments and passivated surfaces.
• Electronics and precision manufacturing: Knoop and micro-Vickers testing of platings, ceramic substrates and thin films.
• Polymers and consumer products: Shore hardness control of seals, tires, footwear, hoses and plastic housings.
• Failure analysis: hardness mapping of fractured or worn parts to detect softening, hardening, decarburization or incorrect heat treatment.

FAQ

How do I select the appropriate hardness testing method?

Selection depends on material type, expected hardness, specimen thickness and surface condition. Use Brinell for coarse or inhomogeneous materials such as castings and forgings, Rockwell for rapid production control of finished metallic parts, Vickers for a single scale spanning soft to very hard materials, microhardness for coatings and weld microstructures, and Shore durometers for elastomers and plastics. When in doubt, follow the scale specified in the product standard or consult accredited third-party laboratories for method development.

What is the minimum specimen thickness required?

As a rule, the specimen must be at least 8 to 10 times the indentation depth for Brinell and Rockwell testing and at least 1.5 times the indentation diagonal for Vickers testing. Any visible marking or bulging on the supporting face invalidates the result, and a thinner sample should be tested with a lower force or a superficial Rockwell scale.

Can hardness values be converted between HBW, HRC and HV?

Approximate conversions are possible using ISO 18265 or ASTM E140 tables, but the relationships are material-dependent and valid only within stated ranges. Converted values should never be used for acceptance decisions where a specific scale is specified; direct measurement in the required scale is always preferred.

How many indentations are required for a valid test?

Most standards require at least three valid indentations, with the mean reported for Brinell and the individual values reported for Rockwell and Vickers. Spacing rules—typically 3 indentation diameters center-to-center for Brinell, 4 diameters for Rockwell and 2.5 diagonals for Vickers—must be respected to avoid work-hardening interaction between adjacent indentations.

How often must a hardness tester be calibrated and verified?

Machines require periodic direct verification of force, indenter geometry and measuring device at intervals defined by the standards, plus daily or per-shift indirect verification using certified reference test blocks. An acceptable error between the block value and the machine reading must be demonstrated before production testing begins.

Which factors most commonly cause measurement errors?

Frequent causes include poor surface finish, insufficient specimen thickness, specimen movement or vibration during loading, incorrect dwell time, worn or damaged indenters, indentations placed too close to edges or to each other, parallax error in optical diagonal measurement, and temperature extremes. Careful control of specimen preparation and machine verification eliminates the majority of these errors and ensures reproducible hardness values.