Hardness testing determines the success of the heat-treatment procedure and the material’s response to that heat treatment. The results of a hardness test can indicate:

  • If the heat treatment was successful
  • Possibly the cause of a failure
  • Other mechanical properties of the metal
  • Whether or not the metal is in a condition that will ensure its functionality
  • A comparison to other hardness values

It is most important that the test is conducted in the appropriate and accurate manner in order to achieve “real results.” The preparation of the metal surface for hardness testing is as important as conducting the test itself. The surface preparation of the metal to be tested is what we will focus on in this multi-part blog.


Typical hardness tester

Metal Surface Preparation

The heat-treatment process or pre-condition of the metal will determine the surface condition to be tested. The metal can be in a condition of having:

  • Surface oxide formation (scale)
  • Surface decarburization (loss of surface carbon due to unstable processing conditions)
  • No surface decarburization
  • Carburization
  • Nitriding
  • Other surface treatments


Fig. 1. Methods of hardness testing