Page 311 - CITS - Welder - Trade Practical

WELDER - CITS

MODULE 9: Inspection & Testing

EXERCISE 83 : Perform & review Hardness Testing

Objectives

At the end of this exercise, you will be able to:
• prepare the surface
• inspect the defect
• check strength
• check Microstructure of a known material.

Job Sequence

- The application of hardness testing enables you to evaluate a material’s properties, such as strength, ductility
and wear resistance, and so helps you determine whether a material or material treatment is suitable for the
purpose you require.
- The definition of hardness testing is ‘a test to determine the resistance a material exhibits to permanent
deformation by penetration of another harder material.’
- However, hardness is not a fundamental property of a material.
- Therefore, when drawing conclusions of a hardness test you should always evaluate the quantitative value in
relation to the given load on the indenter the given load duration and the specific indenter geometry.
- A hardness test is typically performed by pressing a specifically dimensioned and loaded object (indenter) into
the surface of the material you are testing.
- The hardness is determined by measuring the depth of indenter penetration or by measuring the size of the
impression left by an indenter.
- Hardness tests that measure the depth of indenter penetration include: Rockwell, Instrumented Indentation
Testing, and Ball Indentation Hardness.
- Hardness tests that measure the size of the impression left by the indenter include: Vickers, Knoop, and
Brinell.
Wear protective clothing.

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