Investigating the impact of porosity induced by process parameter variations on the tensile properties of 17-4PH parts realized by atomic diffusion additive manufacturing

Atomic diffusion additive manufacturing (ADAM), also known as material extrusion additive manufacturing (MEX), is a promising additive manufacturing technique combining filament extrusion to debinding and sintering processes. This range of metal additive manufacturing processes display advantages in terms of cost and safety compared to other processes using high energy beams and volatile powders under controlled atmosphere. However, ADAM-processed parts display specific porosity features which impact significantly their mechanical properties. The aim of this work is to evaluate the impact of printing parameter variations, through their influence on porosity features, on the tensile properties of ADAM-processed final parts. Specimens made of 17-4PH stainless steel were manufactured using ADAM technology. Two layer thicknesses and three printing orientations were considered. Mechanical properties were investigated by tensile testing combined with digital image correlation. The porous structure of each specimen was characterized by X-ray tomography and scanning electron microscopy. An increase in porosity rate, ranging from 1 % to 10 %, induced by lowering the layer thickness or modifying the printing direction, was associated with a reduction in mechanical properties. Printing direction-related anisotropic mechanical behaviour of ADAM-processed parts was quantified: a 15% decrease in Young modulus value was observed when shifting from a printing orientation parallel to the loading direction to an orientation orthogonal to it. Further investigations in the form of finite element analysis combined with numerical homogenization performed on representative elementary volumes mimicking ADAM specimen porous features would provide perspectives regarding process parameter optimization for prorous structures typical of MEX processes.