Apparent Hardness

Definition - What does Apparent Hardness mean?

Apparent hardness is a type of macro hardness or macro-scale hardness testing. Because powder metallurgy materials are metal and pores, the value of apparent hardness generated when obtained at a macro level refers to the hardness of both as a composite. Hardess refers to the metal's resistance to permanent deformation, and is represented by the unit Rockwell C.

Corrosionpedia explains Apparent Hardness

Due to the differences in gross indentation and structure, the value of hardness or Rockwell in powder metallurgy materials and wrought metals cannot be directly compared. In this case, the indenter passes through the permeable structure, resulting in a lower value of hardness relative to the intrinsic hardness that the metal actually has.

When the hardness values of such materials are obtained on testers that are on a macro-hardness scale, apparent hardness is obtained. This type of hardness is the combined effect of the particle hardness of the metal and its porosity. For instance, a steel treated under heat may have a measure of 40 Rockwell C hardness, while the actual hardness of the material is at 64 to 68 Rockwell C.

The determination of apparent hardness is vital in the selection of materials and processes. With accurate measurements, operators gain information as to whether a certain part should be protected against corrosion, be machined or treated by heat and other things that ensure quality operations and damage protection.

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