Comparative Study On Hardness Behaviour of Quench-Partitioned Ductile Cast Iron

In this research work, the conventional austempering and quench-partitioning (Q-P) heat treatments were applied to ductile cast iron for comparison. The treatment schedules for quench-partitioning treatment was designed and analyzed by applying Box Behnken Design (BBD) route. The microhardness of the samples were measured using Indentec Universal Testing machine. The microstructure evaluation of the selected samples was also performed via Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). The result of the investigation revealed that the quench-partitioning heat treatment carried out at 190 oC quenching temperature and 300 oC partitioning temperature maintained for 10 minutes resulted in highest hardness value (447 HV) as compared to the as-cast and conventional ADI samples. Validations of the models and the optimal parameters showed that their prediction accuracy is within the acceptable limit of 10% prediction error. The single-objective optimized Q-P sample was found to show superior hardness of 449 HV which is equivalent to 102.3% improvement over that of as-cast ductile cast iron for comparison. Finally, quench-partitioning heat treatment was found to improve the hardness behaviour of as-cast ductile cast iron.