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Rockwell Hardness Testing Services
Just like the Brinell Hardness Test, the Rockwell Hardness test, too, implements the indentation manner of testing. The difference between the two tests lies in the higher accuracy and versatility of the Rockwell Hardness test. The ASTM E-18 standard has defined this test and it is the most common method of hardness testing.
In this test, different loads are applied to the indenter to check the permanent depth of indentation that is produced on the specimen’s surface. The indenter is generally a diamond or a spherical ball that is placed over the surface before the application of the minor load.
The minor load ranges from 29.4199N to 98.0665N. This load breaks through the surface to ensure that the surface finish does not hamper with the hardness results obtained. After a specific period, the load is removed and the depth of the indentation is measured.
Once this minor load or ‘preload’ is removed, an additional load is added to reach the optimum test load, which ranges between 147.1N and 1471N. This additional force is held to the surface to give time for the elastic recovery of the material. After the removal of this major load, the depth of the indentation is measured again. The Rockwell hardness values are the difference between the two depths of indentation measured. The distance is converted into a hardness number.
The Brinell hardness number is expressed as the ratio of the load to the measured area of indentation while the Rockwell hardness number is the difference in the depth of the indentation measured by applying two different forces.