Nitriding on alloy steels has many advantages. In order to best apply the many forms of nitriding; Ion Plasma, gas deep case…to name a few, it is important to understand the service requirements, coupled with the desired surface and core properties of the alloys.
For example, deep case nitriding is widely used to provide a deep, hard bed for roller bearing races. Gas deep case nitriding is required in order to survive the very high unit loading of the harder small diameter rollers. This application also needs the added compressive strength of deep case to this bed to minimize the Brinell effect.
However, the gas deep nitriding protocol requires a long duration nitriding time (100 hours) and high temperature, resulting in a very thick “white layer”. The white layer infiltrates the diffusion layer and must be ground away. This post nitride grinding eliminates much of the desired surface residual compressive strength as well. The long duration and high temperature substantially changes the alloy core properties, but the service requirements of roller bearing races can accommodate the change.
In addition, the alloys composition must have high concentrations of certain elements that permit deep case nitride. These element concentrations can and do lead to trade offs’ in core mechanical properties. No problems…as long as those core properties are acceptable for the intended service.