The effect of debinding and sintering parameters on the mechanical and microstructural properties of Fe-2Ni metal injection molded compacts

Abstract

This paper investigates the effect of debinding and sintering parameters on the density, ultimate tensile strength (UTS), hardness and grain size of the Fe-2Ni MIM compact. For this purpose, a wax-based binder system containing PE, PP, PW and SA was adopted for developing the feedstock. After optimizing the feedstock powder loading based on the critical solids loading and studying the homogeneity of feedstock, green parts were injected. The samples were then immersed in the n-hexane solution for different times to investigate the effect of debinding time on the weight loss of binder system. After observing the samples shrinkage behavior, sintering temperatures were selected and the samples were sintered at temperatures of 1050, 1125, 1200, 1275 and 1350 °C. Finally, the microstructure, density and hardness of the sintered samples were evaluated and the UTS of the samples was measured using the DIC technique. The results showed that immersion of samples for 12 h in n-hexane with 50 °C temperature applied as optimum parameters for solvent debinding. In addition, appropriate thermal debinding cycle was designed through the TGA analysis to produce flawless samples. It was observed that the density increases with the sintering temperature increasing, until where in the temperature of 1350 °C the relative density was 97.2%. UTS and hardness values of the sintered samples increased to (∼548 MPa) and (∼144 HV) for the sintered specimen at 1275 °C and decreased at higher temperature. This phenomenon relates to the substantial grain growth in the sintered sample at 1350 °C, as proved by the results of EBSD analysis. Finally, proper sintering condition for Fe-2Ni samples derived through the density, UTS, hardness and microstructural evaluations, so that sintering of the samples at 1275 °C under hydrogen atmosphere showed the optimum condition due to an excellent balance between the mechanical properties and grain size in the samples.