Additive manufacturing of 17-4 PH steel using metal injection molding feedstock: Analysis of 3D extrusion printing, debinding and sintering

The amalgamation of 3D extrusion printing (3DEP) and sintering results in a low-cost process compared to other laser-based additive manufacturing techniques. This work used metal injection molding (MIM) raw material of 17-4 PH steel for additive manufacturing. The 3D printing, debinding, and sintering steps were thoroughly evaluated to achieve the highest sintered density. First, the 3DEP of the MIM feedstock was carried out using a screw-based extrusion system at optimum parameters to acquire the high green density and fine surface roughness. The solvent debinding step was carried out on 3D printed samples to remove water-soluble polymer by immersion method. Thermogravimetric analysis was performed to evaluate the decomposition temperature of the backbone material. Further, thermal debinding and sintering steps were conducted in a single step. The thermal debinding temperature was 500 degrees C, and the sintering temperatures were chosen as 1100, 1200, 1300 and 1360 degrees C. The highest density of similar to 95.6% was attained at a high sintering temperature. The micro-tomography evaluation was carried out on the 3D printed green and high-density sintered samples to evaluate the internal porosity. The mechanical properties and the microstructure were also evaluated for sintered samples. The work opens a way to fabricate metal complex-shaped parts at low cost using market available MIM feedstock.