3D printing of low carbon steel using novel slurry feedstock formulation via material extrusion method

Abstract

Conventional 3D metal printing methods, such as laser sintering and binder jetting are often associated with high initial capital costs that make them inaccessible to many consumers. In this article, an economical alternative approach to 3D metal printing is presented, which uses a slurry-based formulation with the material extrusion method. This method involves a novel slurry feedstock of metal powder and liquid binder, which can be printed at room temperature to form green samples without the need for equipment such as a laser source, binder jetting head, or heated nozzle. It is followed by a thermal treatment process to fuse the printed samples into a metal article. The slurry is prepared by blending carbon steel powder with a cellulose derivative binder and additives. Rheological behaviours of different metal contents and binder concentrations are being investigated to determine the optimum printable slurry formulation. It is found that the optimum slurry feedstock formulation comprises 45 vol% metal content, 54 vol% cellulose derivative binder solution at a concentration of 300 g/L, and 1 vol% defoamer. The resulting slurry has fast-drying shear-thinning behaviour and a high storage modulus of 4 × 107 Pa to sustain the printed article at room temperature. The printed articles exhibited an average linear shrinkage of 12.36%, with less than a 1% linear shrinkage difference between X, Y, and Z directions after thermal treatment. The measured densities of the sintered articles were 95% ± 2% compared to the ASTM B783 (material code F-0000). The sintered articles have a measured carbon content of 0.28 ± 0.02%, hardness of 64.15 ± 9 HV, ultimate tensile strength of 255.33 MPa and Young's modulus of 130.47 GPa. This work demonstrates the viability of this additive manufacturing method in producing metal parts with comparable properties to conventional manufacturing.