Vast attention on producing Inconel 718 (IN718) parts by additive manufacturing (AM) method has been paid in recent years. However, mechanical anisotropy is an important challenge in AM parts to deal with and is the main focus of current researches. The aim of the present work is to study the effect of microstructural anisotropy on the room and high-temperature mechanical properties of selective laser melted (SLM) IN718. Several IN718 cubes were fabricated by selective laser machine and microstructural and mechanical anisotropy were carried-out in as-built, heat treated, and hot isostatic pressed (HIP) conditions. The heat treatment and HIP were done according to AMS5662 and ASTM F3055 standards, respectively. Microstructural investigations were done by optical microscopy, scanning electron microscopy, field emission scanning electron microscopy equipped by electron backscattered diffraction detector, and X-ray diffraction method. The mechanical properties were determined in different directions at room and 650 °C using small punch test. In addition, tensile test specimens were built vertically and horizontally to compare the anisotropy level with the small punch method. The results showed that the nature of melting and solidification leads to the formation of columnar grains along the building direction during the SLM process. The latter resulted in strong cubic texture component and consequently mechanical anisotropy. Mechanical tests revealed that side view sample exhibits 35% grater maximum loads at room temperature. However, top view showed 6% better mechanical properties at high temperature. Also, after standard heat treatment, the degree of anisotropy reduced to 11% at room and 4% at 650 °C. Microstructural observations showed that the columnar grains and all kinds of defects eliminated after HIP treatment followed by precipitation hardening. It also increased the relative density of IN718 parts from 99.50% to 99.96%. Besides, the degree of anisotropy decreased to 3% in room and 2% at high temperatures. Fractography of punched samples shows a ductile surface for the side and brittle for the top view at room temperature. On the contrast, high temperature fracture surfaces are vice versa. The fracture surface of top view represented ductile fracture mode after heat treatments while the side view shows brittle surface. After all, samples subjected to hot isostatic pressing showed ductile fracture surface in all conditions.
