Surface hardening for 38MoCrAl09 steel using fluidized bed nitriding

Abstract

The paper is based an nitriding experiments made in a fluidized bed laboratory furnace. Fluidization was obtained in a steel refractory retort by solid granular (burned fire clay) and fluid (mixture of ammonia and nitrogen). Heating system is based on indirect electrical method. Heating transfer from furnace to retort is high and is determinate by high value of heat transfer coefficient for fluidized bed. Nitriding processes were driven by a classic experimental matrix (ammonia proportion is constant, nitriding time and nitriding temperature are variable). Results were investigated by: hardness HV₅, micro-hardness HV_0,05, microstructure and XRD. The results confirm nitriding process, media capacity for heat and mass transfer and a good behavior of 38MoCrAl09 steel.