Influence of Specimen Layout on 17-4PH (AISI 630) Alloys Fabricated by Low-Cost Additive Manufacturing

Abstract

This work examined the effects of specimen layout on physical, microstructural, and mechanical properties of 17-4PH (AISI 630) fabricated by metal-fused deposition modeling process. Tensile specimens were 3D-printed with the different layouts using 100 pct infill. The as-printed and as-sintered specimens with the flat layout had the best appearance, green, relative sintered density, and sintered tensile properties with good repeatability, while the specimens with the vertical layout were the worst. The as-sintered tensile properties of specimens with the side layout were slightly lower than those with the flat layout but significantly higher than those with the vertical layout. Moreover, the tensile properties of specimens with the flat and side layouts met the Metal Powder Industry Federation standard 35 for metal injection molding. The tensile properties and corresponding fracture surfaces can be explained in terms of the combined effect of load-bearing and stress concentration due to the pre-existence of voids at perimeters. The fracture surfaces of specimens with the vertical layout showed large defects induced during printing and voids between perimeter walls generating high stress concentration and layer delamination. The difference between tensile properties of specimens with the side and flat layouts is mainly due to the characteristic of the printing—voids in the side layout are larger and more detrimental to the mechanical properties—which was confirmed by the evidence of cracking in the fracture surface.