The Phase Composition of the Nickel-based Inconel 718 Alloy obtained by Additive Technology

Introduction. Over the past decade, additive manufacturing (AM) aimed to get the object by 3D model through layer-by-layer manner in a single pass has been actively applied in manufacturing of complex-shaped parts. However, standards for AM materials have not yet been developed. Engineers and researchers are trying to achieve the mechanical properties of AM materials as those formed by standard technologies. Precipitation hardened Ni-based alloys are desirable materials for aircraft engines parts. Usually the complex geometry of such metal parts is formed by a combination of several standard technologies with complex heat treatment. Changing this labor-intensive process to AM is a promising industry direction. Phase transition occurring during layer-by-layer production with a complex thermal effect is one of the main tasks for researches. Focus of this work is made in the study of phase composition and mechanical properties of Ni-based alloy fabricated by high-speed direct laser deposition in different layer areas. Materials and methods. Microstructure of the as-deposited sample is performed using optical microscopy and SEM. Phase composition is analyzed using XRD and TEM. Mechanical properties are evaluated with microhardness and tensile tests at room temperature. Results and Discussion. The as-deposited structure is columnar; grains growing epitaxially along the deposition direction with the presence of transition areas. Laves phase, MC and M23C6 carbides appear as discrete particles and change morphology in different layer areas. The main gamma'/gamma '' phases are not detected. The initial formations of delta-phase are identified. The microhardness test has the standard level value. With the high value of elongation, the yield strength and tensile strength of the as-deposited sample are lower than those of standard.