How do Hardness Testing work?
Hardness expresses resistance to local plastic deformation. In Rockwell testing a diamond cone or hardened ball is pressed in with a preliminary and then a main load, and hardness is read from the additional depth of penetration, which makes the method fast and simple. Brinell testing presses a tungsten carbide ball at a high load and measures the impression diameter optically, giving an average value that suits coarse or inhomogeneous material. Vickers and Knoop testing use a diamond pyramid with loads from grams to kilograms and measure the diagonal lengths of the impression, which allows individual phases, thin cases and small features to be tested. Leeb rebound testing measures the velocity of an impact body before and after striking the surface, giving a portable measurement that is converted to other scales by comparison. The measured value depends on test force, indenter geometry, dwell time, surface finish and support of the specimen, so these are all defined by the standards.
Which Hardness Testing variants are available?
- Bench Rockwell Hardness Tester — A bench Rockwell hardness tester presses a diamond cone or hardened ball into the specimen under a preliminary and main load and reads hardness from the additional penetration depth.
- Digital Vickers Microhardness Tester — A digital Vickers microhardness tester presses a diamond pyramid into the surface with loads from grams to kilograms and measures the impression diagonals optically.
- Brinell Hardness Tester — A Brinell hardness tester presses a tungsten carbide ball of 2.5 to 10 mm diameter into the surface with a high load and measures the impression diameter.
- Universal Hardness Tester — A universal hardness tester performs Rockwell, Brinell and Vickers tests in one frame by changing load, indenter and measuring system.
- Portable Leeb Rebound Hardness Tester — A portable Leeb rebound hardness tester measures the velocity of an impact body before and after striking the test surface and converts the ratio to a hardness value.
How do I choose the right variant?
Select the scale from the material, the size of the feature and the acceptance criteria in your specification. Rockwell C is standard for hardened steel, Rockwell B for softer metals, Brinell for castings and large forgings where the impression is acceptable, and Vickers or Knoop for thin cases, coatings, welds and individual microstructural constituents. Choose the load range to cover your thinnest feature, remembering that Vickers hardness depends on load at low values. Decide whether you need a manual, digital or fully automatic machine: automatic machines with traverses and motorized stages are used for case-depth series and for high volumes, and they should store test programs so that results are repeatable. Portable rebound testers suit field inspection of large parts but need a conversion relationship established against a bench machine on the same material, and they cannot test thin sections or small parts reliably.
Where are Hardness Testing used?
Hardness Testing are specified in hardened and tempered steel acceptance testing, case depth measurement after carburizing or nitriding, casting and forging hardness control, weld and heat-affected zone hardness traverses and field inspection of large components.
Which standards and certifications apply?
Work with Hardness Testing is commonly governed by ISO 6508, ISO 6506, ISO 6507, ASTM E18, ASTM E10, ASTM E384, ASTM E140 and IEC 61010-1. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Verify each tester daily or per shift with a certified reference block whose hardness lies close to the working range, and record the reading, the block identity and the date. Have the machine verified annually for test force, indenter geometry, depth or optical measurement and timing, either in house with traceable devices or by an accredited body. Handle indenters carefully, inspect them for chipping, and replace damaged ones, since a chipped diamond or flattened ball biases every result. Prepare surfaces by grinding or polishing to the roughness stated in the method, support thin specimens rigidly and ensure the surface is perpendicular to the indenter. Report the scale, test force, dwell time and number of readings with every result, and treat scale conversions as estimates rather than equivalent values.
