The result of hardness testing is what is used as the first level of interpreting the correctness of the heat-treatment procedure. The results of a hardness test can indicate:

  • If the heat treatment was successful
  • The cause of a failure
  • Other mechanical properties of the metal
  • If 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 and that the appropriate hardness test method is used in order to achieve the “real results.” Figure 1 provides a categorization of hardness test methods.

 

Steel Surface Preparation  

The preparation of the metal surface for hardness testing is of as much importance as conducting the test itself. The surface preparation of the steel to be tested is what we will be focusing on in part 1.

The heat-treatment process or pre-condition of the steel will determine the surface condition to be tested at that point. The surface condition of the steel could be, of course, any one of the following: surface oxide formation (scale), surface decarburization (loss of surface carbon due to unstable processing conditions), no surface decarburization, carburized, nitrided or other surface treatments.

We will discuss sample surface issues and preparation next time in part 2.