Taguchi DoE analysis and characterization of 17-4 PH stainless steel parts produced by material extrusion (MEX) process

Abstract

Material extrusion (MEX) of metallic components is an indirect additive manufacturing (AM) process that is recently gaining a lot of attention in the industry. This multi-step process with debinding and sintering, provides an inexpensive safe alternative, that is effective, flexible and office-friendly for several corporations compared to other metal AM techniques. However, optimizing the manufacturing parameters of the MEX process is still challenging due to the lack of research on their impact on the mechanical and surface properties of the fabricated materials.

For this purpose, this paper investigates how various processing parameters impact the mechanical properties and surface roughness of 17-4 PH stainless steel parts produced by MEX. The parameters analyzed include layer thickness, build orientation, number of contours, and aging thermal treatment for 1 h at $482°C$ (H900). A Taguchi design of experiments (DoE) was employed to conduct the parametric analysis and the results were post-evaluated via the analysis of variance (ANOVA). The experimental results show that H900 treatment increases the micro-hardness by ∼50 HV_0.3 and contributes in augmenting the ultimate tensile strength (UTS) by ∼200 MPa. The build orientation and its interaction with the layer thickness have the highest impact on the surface roughness. Moreover, the amount of enclosed porosity is higher in the samples with lower layer thickness. The absorbed impact energy ($W_{abs}$) is relatively low due to the enclosed porosity content and is not linked to the analyzed processing parameters. The best mechanical properties were obtained for parts built with solid infills, 0° build orientation, 0.125 mm layer thickness, two contours, and H900 as a post-treatment.