Hardness Tests on Materials

Hardness tests are preferred for their ability to provide insights into the tensile strength of materials without significantly damaging the sample and with relatively short execution times. There are different scales for measuring a material’s hardness, each with a specific approach, such as the Brinell, Vickers, and Rockwell scales. Thanks to the Unit Converter by Bonomi Acciai, available on our website, users can easily convert hardness values from one scale to another.

The Brinell method is widely used for softer materials, such as medium-low alloy steels and light alloys. It is based on the application of a steel or hard metal ball against the surface of the test piece, with a predetermined force, for a specific period of time. After the load is removed, the average diameter of the indentation left on the surface is measured.

The most common configuration involves the use of a 10 mm diameter ball and a load of 3000 kg. However, for softer materials, the load can be reduced to as low as 50 kg (49N) to prevent the ball from penetrating entirely into the sample.

An example of Brinell hardness is: 320 HBW_10/3000, and:

• 320: the calculated hardness value;
• HB: symbol for Brinell hardness;
• W: indicates the indenter material, in this case hard metal;
• 10: the diameter of the indenter in mm;
• 3000: the applied load in kg.

The Vickers test is ideal for microhardness and uses a square-based pyramidal indenter. This method is used where the Brinell method is not applicable and requires a precise surface preparation and indentation reading process, often carried out with the aid of a microscope. The Vickers test is essential for finished machined parts, small-sized components, parts subjected to surface thermochemical treatments, and laboratory measurements.

The Rockwell method differs from other methods because it measures the depth of the indentation left by the indenter, rather than its size. This makes it a fast and advantageous process, as the hardness value can be read directly without the need for optical analysis. However, its accuracy can be affected by small errors in depth measurement.

Hardness tests are essential to ensure that the materials used are capable of withstanding the most demanding application conditions. Visit our website to discover how our Unit Converter can simplify your hardness value conversion operations.