Additional Substrate Heating in Direct Laser Deposition of Inconel 738

The paper is devoted to the study of the process of direct metal deposition of nickel alloy Inconel 738. It is shown that the use of additional substrate preheating to 750°C prevents crack formation in the material. The influence of additional heating during the deposition process on the structural-phase composition of the formed material is studied. It is demonstrated that additional heating promotes an increase in the grain size, as well as changes in their shape and growth direction. The microstructure is studied using electron microscopy, and the distribution of alloying elements within and at grain boundaries is investigated depending on the substrate preheating temperature. Using synchrotron radiation, it is established that preheating the substrate to 750°C during direct laser deposition of Inconel 738 leads to the formation of M23C6 carbides and the enrichment of the metal matrix with the strengthening γ' (Ni3Al) and γ'' (Ni3Al) phases. Data on the change in the temperature gradient and the cooling rate of the melt pool depending on the substrate temperature are obtained. The mechanical properties of the resulting specimens are measured: hardness, microhardness, wear resistance, and friction coefficient. The substrate preheating contributes to an increase in hardness by 48%, microhardness by 55%, and wear resistance of the obtained coating by 35%.