262.723.3345 kim@hudapack.com

The term “Neutral Hardening” is to have a component be heated above temperature Acɜ, in a protective atmosphere, to achieve a complete transformation to 100% austenite for the material being processed.

The atmosphere must be conditioned and the carbon potential setpoint is the carbon content of the material’s chemical composition.

Setting the carbon potential accurately is important.

  • Too low of a setpoint and decarburization of the part surface will occur.
    • If this occurs a carbon restoration cycle must be run to “correct” the surface carbon content.
  • Too high of a setpoint will cause carburization of the part surface.
    • Under this scenario the engineering group must analyze the hardness and mechanical properties of any mating part before accepting this carburized condition.

Heating the material above the Acɜ temperature and staying above this temperature for the assigned time period is critical to form 100% austenite then rapidly cool the component to transform the microstructure to 100% martensite.

  • There are alloy materials that do not 100% transform to 100% martensite. Meaning there is austenite that did not transform.
    • This microstructure is called having “retained austenite”.
      • Cryo treatment does help transform this remaining austenite however customer approval by their engineering group must be had.
    • The “retained austenite” can be viewed under microscopic evaluation.