Many products are generated constantly to serve the industry and various other purposes that contribute to the advancement of society.
The majority of these products are made up of high-tech materials that need to be assessed and evaluated.
The materials used for creating these products need to be tested before they are made into use. One of the most important methods to determine the properties of the material is hardness testing.
The material hardness is the property that enables it to resist bending, deformation, abrasion, cutting, or scratching.
Whether you receive the products from the third-party suppliers or you are going to step into the production process of your products, hardness testing is one of the most crucial steps that must not be avoided.
Hardness tests are performed on materials that measure the indentation depth left by a point with a specific force of a specific shape and for a specific amount of time.
Hardness tests are performed to determine if the materials while performing their indented duties will be able to survive or not.
There are several tests used to determine the hardness of materials and to determine the size of the impression left by the test and hardness. One of the renowned tests is named as superficial hardness test or superficial Rockwell hardness test.
What is Superficial Rockwell hardness test
Rockwell Superficial hardness tests are generally used for the materials that are too small or thin such as coatings, thin strips or carburized surfaces, etc.
Deduced preload (3kgf) and reduced loads (15 kgf, 30 kgf) that are used as a major load is used in the Superficial Rockwell hardness test.
How does it work?
The method of Superficial Rockwell hardness test consists of indenting the material to be tested with a hardened steel ball indenter or a diamond cone.
Under a preliminary minor load that is usually of 3 kgf, the indenter is forced into the material to be tested.
An indicating device following the movements of the indenter responds to changes in the depth penetration of the indenter when the equilibrium is reached. This indicating device is then set to a datum position.
A resulting increase in the penetration is formed while the additional major load is till applied to the preliminary minor load. The preliminary minor load is maintained while again equilibrium is reached, whereas the additional major load is removed.
The depth of penetration is reduced, allowing partial recovery after the removal of additional major loads.
The permanent increase in the depth of penetration is used to calculate the Rockwell Superficial hardness number that results from the application and removal of the additional major load.
How is it different from the standard Rockwell hardness test?
The primary difference between the standard Rockwell hardness test and Superficial Rockwell hardness test is that in Rockwell, the pre force is always 10 kgf whereas, in Superficial Rockwell, the pre force is 3 kgf.
Also, the main force or total test force in standard Rockwell hardness test can vary between 60, 100, or 150 kgf.
Whereas, in the Superficial Rockwell hardness test, it can vary between 15, 30, and 45 kgf.
One important point to consider is that the hardness values determined by standard Rockwell hardness test can be converted to Superficial Rockwell hardness test values and vice versa.
Superficial Rockwell method is more commonly used in Europe while it was invented in the USA.
The superficial hardness test is primarily used to test thin layers or components or the materials whose calculated hardness value is outside the standard Rockwell scale.
Importance of Superficial hardness test
There are several thin, soft, and small materials that need to be tested before they are made into use for production purposes.
Hardness tests are considered to be universally valuable mechanical tests that are available to engineers across the globe.
The primary importance of these tests is that they are relatively inexpensive and simple to be conducted, providing a wealth of data and information regarding the material.
Superficial hardness tests hold prime importance in hardness testing methods as it generates the finest results of the thinnest or smallest materials and obtains accurate and highly sensitive readings.
The superficial hardness testers are perfect to be used for workshops, laboratories, inspection labs, and tool rooms, etc. to serve various purposes.
Most of the superficial hardness testers are conformed to ASTM E18 standards.
These standards are formed to get the products according to the international cooperative functioning to enhance the specific strategic procedures performance that results in greater confidence in technical objectives.
Superficial Rockwell hardness tests are extensively used to determine the hardness of soft and thin materials that require minute detailing of the specimen.
There are various superficial hardness testing machines available in the market that comes with efficient superficial hardness scales such as HRN, HRT, etc. that use different types of indenters.
Also, there are several motorized versions available for superficial hardness test to confirm the accuracy of results.