Development of Applications of Infrared Heating in Ferritic Salt Bath Nitrocarburizing Process

Abstract

Abstract A rapid salt bath nitrocarburizing process technology is primarily developed by providing infrared heating instead of conventional induction heating. Two thermochemical techniques, conventional salt bath nitrocarburizing with induction heating and salt bath nitrocarburizing with infrared heating, were done on AISI 1018 low-carbon steel. The results showed that infrared heating could significantly enhance the nitrocarburizing efficiency and shorten the holding time comparing with the conventional nitrocarburizing process. Nitrocarburizing time has been shortened from 120 min to 90 min in infrared heating technique, and a more intense carbon-enriched compound layer is observed in field emission scanning electron microscope micrographs when compared to the conventional nitrocarburizing process. Energy dispersive X-ray spectroscopy analysis reveals higher weight % (1.18 %) and atomic % (2.85 %) of nitrogen in infrared-heated nitrocarburizing process specimens as compared to weight % (0.96 %) and atomic % (1.92 %) in conventional nitrocarburizing specimens. A line scan mapping of compound layer and diffusion zone was done to find out the elemental intensities and results favored by infrared heating specimens. Furthermore, an increase in microhardness was observed because of the thick and compact compound layer in infrared heating. Also, more profound diffusion zone was observed as compared to the conventional nitrocarburizing process. Further, surface roughness values have been found to be very high because of the highly porous surfaces created by the postoxidation process, and this could also be attributed to higher radiant energies from infrared heating.