THE STUDY OF THE STRUCTURE AND PROPERTIES OF SPECIMENS OF INCONEL 738 HEAT-RESISTING ALLOY OBTAINED BY THE SELECTIVE LASER MELTING TECHNIQUE (SLM)

Currently, the selective laser melting technique (SLM) with the use of powder metallic materials is a promising area in the aircraft and engine technology. Due to this technique, it is possible to produce parts with any complexity configuration at fewer expenses for tooling and mechanical processing and the prototyping of goods becomes simpler as well. The issue of application of powder materials of heat-resisting alloys in the additive production is particularly topical, which is due to the problems caused by their complex chemical composition, insufficient thermal conductivity, and shrinkage tendency. The paper studies the influence of laser output power on the microstructure and properties of specimens of Inconel 738 heat-resisting nickel alloy produced with the help of a commercial 3-D printer using the SLM printing technology. Moreover, the authors considered the way of improvement of the specimens’ mechanical properties through the improvement of microstructure after SLM and further heat treatment. The authors carried out the metallographic and electron microscopic study of the initial material and the specimens grown using the SLM technology at the laser output power of 75, 100, 125, and 325 W; analyzed the microstructure evolution in the result of heating caused by the growth of supply energy. Further heat treatment made it possible to study the influence of step quenching on the microstructure and mechanical properties of specimens. Further heat treatment made it possible to study the influence of step quenching on the microstructure and mechanical properties of specimens. The authors determined the optimum technological parameters of laser emission to produce parts from Inconel 738 heat-resisting alloy using the SLM technique and produced parts with the minimum quantity of the defects. The study identified that heat treatment, including step quenching, improves the mechanical properties - ultimate resistance, yield limit, and percent elongation - through the “healing” and the defects’ size reduction.

Inconel 738, heat-resisting nickel alloy, microstructure, selective laser melting, electron microscopy, Inconel 738