In nitriding and ferritic nitrocarburizing (FNC), the critical components are temperature, ammonia and carbon. The control variables are defined as K_N (nitriding potential) along with K_c (carbon activity). Using readily available technology, both K_n and K_c can be measured and controlled. Sensor technology, along with automated programmable control, eliminates variability in process and provides repeatable quality results. In this article, the author discusses the basic principles of controlling K_N and K_C by utilizing and understanding sensor and control technology. Analysis of the input variables is discussed as they are associated with nitriding and FNC applications. Also, the effects of the gas ratios, temperature and time on actual results are discussed. Review of processes using hydrogen sensors, CO/CO_2 and oxygen probes is provided. The author also discusses the technical challenges and maintenance requirements for those sensors and processes.
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