Optimization of the CEM printing process for a 16MnCr5 and Analysis of the Material behavior during debinding and sintering

Composite extrusion modeling (CEM process) combines the metal injection molding process (MIM process), which is already established worldwide, with the process technologies from additive manufacturing. It is largely evolving into a technology with production possibilities for products of different sizes, with high accuracy and more complex geometries. 16MnCr5 case hardening steel is typically used and its material properties are well known and understood. However, the resulting material properties following the printing, debinding and sintering sequence must be taken into consideration as it is a sensitive process for the temperatures reached and porosity can compromise the mechanical properties of the component. This paper presents a study on the processing of feedstock composed of 16MnCr5 with a binder of 6.8%, formed by (beheic acid, polyamide and plasticizer). The printing carried out with an ExAM 255 printer (AIM3D, Rostock, Germany) is optimized, by varying the extrusion multiplier and temperature parameters of the nozzle, to obtain the maximum possible density. A map given by the Design of Experiments (DOE) has been created which allows to identify the influences of the parameters on the basis of statistical models that have been obtained through regression analysis. The speed of the chemical debinding, carried out in acetone, is examined as a function of the geometric dimension and the surface area / volume ratio. Sintering was performed on the optimized molded sample to fabricate a dense copper part and analyze linear shrinkage during sintering. Tomography scans and light microscope analyzes were used to analyze porosity and voids in the printed samples with optimized parameters. High-density sintered steel components and gears were obtained with optimized printing process parameters, whose hardness values ​​were evaluated by instrumented indentation.