Effect of TiB2 content on microstructure and mechanical properties of GH3536 superalloy formed by laser solid forming

Abstract

In this paper, GH3536 and TiB2/GH3536 alloys were prepared by laser solid forming(LSF). The effects of TiB2 content on the microstructure and mechanical properties of as-deposited samples were investigated. The results show that, with the increase of TiB2 content in the as-deposited samples, the molten pool boundary becomes shallower, the dendrite structure grows coarser, and the grain size gets larger. Meanwhile, phase segregation intensifies at the interdendritic and grain boundaries. The shape and types of the precipitated phases change significantly: the strip M23C6 carbide phase progressively evolves into a network phase of M23C6 carbide, M2B boride, and Mo-rich phase. Besides, the grain size of the solid-solution samples becomes smaller, and the columnar grains in both sample groups tend to be equiaxed. Interdendritic precipitates undergo a morphological change from a continuous network to a granular one as they gradually dissolve into the matrix. The microhardness of both sample groups also rises, and their elongation gradually declines as the amount of TiB2 increases. However, the tensile strength trend exhibits the opposite fluctuation, as the tensile strength of as-deposited samples drops and that of solid-solution samples increases with the increase of TiB2 content.