Influence of energy density on the microstructure and mechanical properties of GH5188 superalloy formed by laser melting deposition

Cobalt-based superalloys have been widely used in manufacturing high-temperature parts of gas turbine missiles, such as combustion chambers, exhaust nozzles, and heat exchangers in the nuclear energy industry. In order to meet the requirements for rapid manufacturing of these large-scale and high-performance components, the laser melting deposition (LMD) technology has attracted great attention in recent years. At present, the printability evaluation of Cobalt-based superalloys powder needs in-depth study. In this study, a cobalt-based superalloy (GH5188) has been additively manufacturing by using LMD for the first time. The self-designed gas atomization equipment is used to prepare GH5188 alloy powder, LMD technology is used to prepare as-deposited samples, the key process parameters and the resulted microstructure and mechanical properties are investigated. The results show that as the energy density increases, the pores and unfused defects of the as-deposited GH5188 sample decrease. The microstructure of the GH5188 sample is composed of columnar dendrites grown epitaxially, and carbides are precipitated in the grain boundaries and inside the crystals. As the energy density increases, the columnar crystals of the GH5188 sample are obviously thicker, and the hardness and elongation of the sample increase significantly. When the energy density is 70J/mm, the tensile strength of the sample can reach 806.3MPa; when the energy density is increased to 80J/m, the elongation of the sample is 33.01%