Hardness testing methods overview

Here you will find useful information on the basics of hardness testing, the most common standardized test methods Rockwell, Brinell, Vickers and Knoop as well as other test methods such as carbon, plastic and Leeb testing.

Rockwell

This is a depth difference method.

Rockwell

Vickers

It is one of the optical processes.

Vickers

Knoop

Developed as an alternative to the Vickers method.

Knoop

Brinell

Has a test load range from 1 to 3000 kgf.

Brinell

Rockwell

Categorisation of the Rockwell method

The Rockwell method is a static hardness testing method, which can be further characterised as follows:

It is one of the standardised procedures (ISO 6508, ASTM E18).
The process is used to test hardness in the macro range (test force >= 49.03 N), more precisely with a test force of 29.42 to 1471 N.
It is a differential-depth method. This means that the residual depth of indentation left by the indenter is measured to determine the hardness value of a test specimen.
Indenter shape and material: Depending upon the specific Rockwell method employed, the indenter is either a diamond cone (with a cone angle of 120°) or a hard metal ball (with various diameters depending on the method).

Vickers

Basically, it can be said that the Vickers method is increasingly becoming the most common method in practice due to its wide range of possible applications, even if sample preparation is necessary and the evaluation of the hardness value is time-consuming.

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Hardness Knowledge Overview

Knoop

Categorisation of the Knoop method

The Knoop method is a static hardness testing method, which was developed as an alternative to the Vickers method and is used in particular for the testing of thin layers and brittle materials. It can be characterised as follows:

It is one of the standardised procedures (ISO 4545, ASTM E92, ASTM E384).
The Knoop method has a test load range of 1 gf to 2 kgf according to ISO and ASTM, which means that this method can be used for hardness testing in the micro and low-load ranges.
It is an optical method. This means that the size of indentation left by the indenter is measured to determine the hardness value of a test specimen.
Indenter shape and material: The indenter consists of a pyramid-shaped diamond with a rhomboid base, with a longitudinal edge angle of 172.5° and a transverse edge angle of 130°.

Categorisation of the Brinell method

The Brinell method is a static hardness testing method, which can be characterised as follows:

It is one of the standardised procedures (ISO 6506, ASTM E10).
The Brinell method has a test load range of 1 to 3000 kgf, which means that this method can be used for hardness testing in the low-load and, above all, macro ranges (conventional range).
It is an optical method. This means that the size of indentation left by the indenter is measured to determine the hardness value of a test specimen.
Indenter shape and material: The indenter is a tungsten carbide metal ball, with a diameter of 1, 2.5, 5 or 10 mm, depending upon the specific Brinell method.

Further test methods

Plastic testing

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Carbon testing

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Leeb test

The determination of the hardness of metallic materials according to Leeb is defined in the ISO 16859 and ASTM A956 standards. In this dynamic test method, the ratio of rebound velocity to impact velocity of a moving impact body is used to determine the hardness.

Legend:

A Peak value of approach phase
B Peak value of rebound phase
t Time
U Voltage