Real improvements to measuring and control equipment in the past decade have given way to a new generation of expert systems capable of demystifying nitriding and nitrocarburizing processes.

These systems use intelligent multi-sensor measuring devices to precisely determine the atmosphere potentials KO, KN and KC, with the added ability to measure several potentials simultaneously. Devices have a built-in mathematical model that calculates the atmosphere partial pressures and the influence of temperature, atmosphere and time on various steels. This approach enables online prediction of the composition of the compound layer in size, phase and properties. Also, the use of fast predictive control algorithms helps these systems to achieve exact atmosphere control, something that is impossible with classical PID control. More advanced expert systems can also include a process builder application which uses a sophisticated reverse model to target the white layer based on the composition of nitrogen and carbon percentage.The paper will provide an overview of current process controls, explain the influence of potentials and various process set-ups on material, as well as review the differences in classical PID control and predictive control based on the results of a two-year study using laboratory and industrial equipment.