Multi-Objective Optimization of Process Parameters in Pack Siliconizing on AISI D2 Steel

Abstract

In this study, the formation of the silicon coating on the AISI D2 steel with the pack siliconizing method has been investigated. To do so, different times (2, 3, 4 h) and temperatures (650, 800, 950 °C) for heat treating, and Si (8, 10 and 12 wt%) with the same percentage of NH4Cl and NaF (0.5 + 0.5 wt%), and balances Al2O3 halide activator were used. For characterization of coating, SEM (thickness, EDX), XRD, and micro-hardness were used. Based on the experimental results, by increasing time, temperature, and silicon percentage, thickness of the coating, and micro-hardness and percentage of the silicon with the EDX are increased. To run optimization, a Central Composite design, CCD, was used to find the best combination of parameters. Eventually, the optimal combination of parameters was introduced then verified. According to optimization, 4 h holing time, 11.744 Si percentage and 950 degree Celsius are the best combination of process parameters.