Rapid manufacturing of biodegradable pure iron scaffold using amalgamation of three-dimensional printing and pressureless microwave sintering

In the present work, a rapid tooling process using three-dimensional printing and pressureless microwave sintering has been developed for the fabrication of biodegradable pure iron. Carbonyl iron particles were used for sample preparation and phosphate-based investment material was used for mould fabrication. Cylindrical samples were fabricated successfully using the developed rapid tooling process. The fabrication experiments were planned based on response surface methodology to evaluate the effect of microwave sintering parameters, namely sintering temperature, heating rate and soaking time on sintered density, shrinkage and compressive yield strength. The results showed that sintered density and compressive yield strength increased with the rise in sintering temperature from α to γ iron transformation temperature and were found to decrease with further rise in temperature. The shrinkage was found to increase with the increase in sintering temperature. Moreover, with the increase in soaking time and decrease in heating rate, sintered density, shrinkage and compressive yield strength were found to increase. Scanning electron microscopy and the X-ray diffraction plot of the fabricated iron samples showed that even without the application of pressure proper bonding of carbonyl iron particles was achieved. Mould material contamination or oxidation was not evidenced in the experiments. A multi-objective optimization using genetic algorithm was performed to obtain optimum microwave sintering parameters for maximum sintered density as well as compressive strength and minimum shrinkage. A case study on the fabrication of scaffold for human skull was performed to test the efficacy of the developed rapid tooling process.