Hardness is a characteristic that applies to a range of materials metals and nonmetals alike and is defined as the resistance of the material to deformation, penetration, scratching, or other physical force. Element's experts measure hardness according to the requirements of the material and its applications, with equipment precisely calibrated to the appropriate hardness scales.
The straightforward, timely, and relatively non-destruction nature of hardness testing make it one of the most popular characteristics for engineers interested in materials selection, lot verification testing, the evaluation of material processing, or the comparison of hardness values across multiple material samples. In addition, hardness values can typically be closely correlated with other material properties, such as tensile strength.
Macrohardness and Microhardness Testing
Element’s expertise in static deformation hardness methods include both macrohardness (applied loads of more than 1 kg) and microhardness (applied loads of less than 1 kg) in accordance with a wide range of industry standards, most of which call for the use of an indenter of known geometry and mass which is forced into the material’s surface. The amount of force applied along with the depth of the indentation is recorded and used to calculate the appropriate hardness value for a given point on the sample.
On-site Hardness Measurements and Portable Hardness
As part of our On-site Metallographic Analysis, we use portable versions of hardness testing to make on-site hardness measurements on large installations or equipment that are either impossible or impractical to ship to a laboratory. We carry out on-site hardness measurements with the following methods:
Element can prepare the surface for each of the above methods and advise you on the most suitable method for your specific project needs. With global access to a team of multidisciplinary engineers and the advanced testing equipment, our hardness measurement services offer the portability, flexibility and high performance for on-site metals verification.
Brinell hardness testing (ASTM E10 and ISO 6506-1) is the oldest hardness method still in common use. The Brinell instrument employs a larger indentor ball (typically 10mm in diameter) and a much higher load (up to 3,000 kgf) than most other hardness test methods.
The larger indenter helps ensure that hardness readings are not adversely affected by small surface flaws. Because of this, Brinell hardness testing is frequently used on rough materials with a large number of surface imperfections, such as castings and forgings.
Rockwell hardness testing (ASTM E18 and ISO 6508-1) is generally considered to be the most popular and accurate of all hardness methods. Using a ball or cone shaped indentor, Rockwell hardness is used on metals of all types, except for any material with an irregular structure or surface variations that might influence test results.
The Rockwell method, which is detailed in ASTM E18 and ISO 6508-1, involves the use of a diamond indenter to apply a smaller preload on the material. This preload breaks through the material’s surface to eliminate the effects of any surface treatments. After the preload, the major load is applied to complete the test.
Knoop and Vickers (ASTM E384) are the two most common scales of microhardness testing. These tests use light loads and small indenters, making them ideal for small samples, very thin materials, surface coatings, or for evaluating the case hardness of a material through a series of indentations that create a hardness profile.
In accordance with ASTM E384, the Vickers hardness method utilizes a pyramid-shaped diamond indenter. In Knoop microhardness, the indenter is rhombic-pyramid-shaped for longer, shallower indentations.