Difference between rockwell, brinell, vickers and knoop hardness test
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Transcript of Difference between rockwell, brinell, vickers and knoop hardness test
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Difference Between Rockwell, Brinell, Vickers and Knoop Hardness Test
https://pursuitengineering.blogspot.com/2016/12/difference-between-rockwellbrinellvicke.html
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Introduction
Hardness is the property of a material that enables it to resist plastic deformation, usually by penetration. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting
The usual method to achieve a hardness value is to measure the depth or area of an indentation left by an indenter of a specific shape, with a specific force applied for a specific time
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Hardness Tests
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Rockwell Hardness Test No specimen preparation required
Hardness value directly readable, no optical evaluation required
Quick & cost-effective process
Non-destructive testing
Not always the most accurate hardness testing method
The test location must be completely free of all contamination (e.g.
scale, foreign bodies or oil
The indenter has unknown effects on the test results
With increasing hardness, it becomes increasingly difficult to
distinguish between materials
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Rockwell Hardness Test
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Brinell Hardness Test The specimen surface can be rough
Good illumination of the test indent is important for ensuring correct evaluation
of the test indent (e.g. with the aid of a ring light).
The process is slow (by comparison with the Rockwell method). The test cycle
takes somewhere between 30 and 60 seconds
Limitation in applying the method on thin specimens of very hard materials
High risk of deforming the material to be tested when testing in the macro
range with high test loads
The surface quality of the specimen must be good, because the indent is
measured optically
Relatively large test indents that are easier to measure the rather small
Vickers indentations
Can be used for testing non-homogeneous materials (e.g. castings)
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Brinell Hardness Test
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Vickers Hardness Test Specimens need to be prepared
Due to the need to conduct optical indent evaluation,
Vickers hardness testers must be equipped with an optical system
The process is rather slow. The test cycle takes somewhere between 30
and 60 seconds
Non-destructive testing is possible
More expensive to purchase than Rockwell testers due to optical system
The surface quality of the specimen must be good (ground and polished)
Only one type of indenter
The Vickers method can be used with any and all materials and test
specimens
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Vickers Hardness Test
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Knoop Hardness Test Specimen should be polished
Evaluation is more precise than the Vickers method,
Must be equipped with an optical system
The process is rather slow (compared with the Rockwell method). The test cycle takes
somewhere between 30 and 60 seconds
The test is non-destructive
More expensive to purchase than Rockwell testers
The surface quality of the specimen must be good, because the indent is measured
optically
There is only one type of indenter
It is particularly suitable for testing small, longish components and very thin layers as
well as brittle materials (glass and ceramics) for which no other method is appropriate.
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Knoop Hardness Test
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