ORIGINAL ARTICLE A comparison of the tensile, fatigue, and fracture behavior of Ti–6Al–4V and 15-5 PH stainless steel parts made by selective laser melting H. Khalid Rafi & Thomas L. Starr & Brent E. Stucker Received: 14 February 2013 / Accepted: 28 May 2013 # Springer-Verlag London 2013 Abstract In this work, Ti–6Al–4V and 15-5 PH steel samples were fabricated using selective laser melting (SLM) and their tensile, fatigue, and fracture properties were analyzed and compared. The tensile properties were compared with respect to the build orientation. The horizontally built samples showed relatively better tensile properties as compared with the verti- cally built samples. Fatigue performance was studied for the vertical build orientation and compared with standard wrought material data. The tensile and fatigue performance of SLM- built materials were comparable to their respective standard wrought materials. Fractography was carried out for all tensile and fatigue-tested samples. The fatigue fracture behavior of Ti– 6Al–4V was different from 15-5 PH steel. For Ti–6Al–4V, the fatigue crack initiation occurred deep in the subsurface whereas for PH steel the fatigue crack was initiated from the surface. Keywords Fatigue . Fracture . Fractography . Additive manufacturing . Selective laser melting . Ti–6Al–4V . 15-5 PH steel . Direct metal laser sintering Abbreviations SLM Selective laser melting OM Optical microscopy SEM-SE Scanning electron microscopy–secondary electron YS Yield stress UTS Ultimate tensile strength 1 Introduction Selective laser melting (SLM) is an additive manufacturing process for building metallic parts [1]. The process is attracting considerable interest because of its capability to quickly fabricate complex metallic parts directly from a CAD model. In this process, the parts are built in a layer by layer fashion when a high-power laser beam scans over a metallic powder bed and selectively melts the powder. The melted powder solidifies and cools quickly forming a layer of the part to be produced. On completion of each layer, powder is added and laser scanning is repeated to build the subsequent layers until the product is completed. The un- melted powder in the bed acts as a support as well as a path for heat conduction. Residual stresses built up in the part necessitate that supports be used to attach the part to a rigid base-plate so that the part does not move in the powder bed or distort significantly. Like other additive manufacturing techniques, layer-wise production enables SLM to produce complex geometrical features that cannot be obtained using conventional methods. The influence of process parameters and scanning strategy on the development of the microstructure dur- ing SLM of Ti–6Al–4V was studied by Thijs et al. [2]. The microstructure was significantly affected by the high localized heat inputs and the very short interaction times. The local heat transfer conditions determine the orientation of the grains. The process conditions like scanning velocity, hatch spacing (the distance between two adjacent scan vectors), and scanning strategy also have a significant role in determining the grain orienta- tion and grain size. Because of the very high cooling rate, the resulting microstructure was composed of an acicular martensitic phase. Previous work performed by Yadroitsev et al. [3], Morgan et al. [4], and Yasa et al. [5] have provided details on the influence of substrate, energy input, laser H. K. Rafi : T. L. Starr : B. E. Stucker J.B. Speed School of Engineering, University of Louisville, Louisville, KY 40292, USA B. E. Stucker (*) Computer Aided Engineering, Department of Industrial Engineering, JB Speed School of Engineering, University of Louisville, Louisville, KY 40292, USA e-mail: brent.stucker@louisville.edu Int J Adv Manuf Technol DOI 10.1007/s00170-013-5106-7