Atmospheric pressure carburizing and neutral carbon potential annealing in nitrogen containing small additions of hydrocarbon gases can offer cost and steel surface quality alternatives to the comparable, endothermic atmosphere or vacuum operations. An experimental program was conducted for refining real-time process control methods in carburizing of AISI 8620 steel under N2-C3H8 blends containing from 1 to 4 vol% of propane at 900°C and 930°C. Multiple types of gas analyzers were used to monitor residual concentrations of H2, CO, CO2, H2O, O2, CH4, C3H8, and other hydrocarbons inside furnace. A modified shim stock technique and the conventional oxygen probe (mV) were additionally evaluated for correlation with gas analysis and diffusional modeling using measured carbon mass flux values (g/cm2/s). Results of this evaluation work are presented.

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