Experimental Study of Build Orientation in Direct Metal Laser Sintering of 17-4PH Stainless Steel

The current work investigates the micro- and macrostructural integrity of layered structures of 17-4PH stainless steel powders manufactured using direct metal laser sintering (DMLS). More specifically, a vacuum solid-state sintering method accompanied with a powder layering process has been employed. Tensile specimens manufactured according to standard ASTM E8 using additive manufacturing were grown at different orientations so as to realize their effect on the overall microstructural integrity. The 40-mu m-thick parts were manufactured using a 500 W laser beam to sinter the powder in a vacuum and nitrogen atmosphere. Melt pools were controlled by limiting the laser intensity to 65% and the focal length range was adjusted between 3.4 and 4.6 mm to control the induced spark and reduce oversintering of the powdered layer. The tensile properties and density as well as micro- and macrohardness for the manufactured samples have been measured and analyzed. Furthermore, microstructural analysis of the undeformed and fracture surfaces of the layered 17-4PH stainless steel made by the DMLS process was conducted by means of X-ray diffraction, optical microscopy, and scanning electron microscope. Moreover, a comparative analysis with traditionally manufactured samples was carried out to set a benchmark for the use of additively manufactured stainless steel. The horizontally grown tensile specimens seemed to yield better results than diagonally grown specimens; however, the wrought specimens seemed to supersede both in terms of mechanical properties.