Preparation of Ni–Ti composite powder using radio frequency plasma spheroidization and its laser powder bed fusion densification

Abstract In this study, spherical Ni–Ti composite powder was synthesized from blended elemental Ni and Ti powders using radio frequency plasma spheroidization process. The effects of powder feeding rate and carrier gas flow rate on the spheroidization efficiency and Ni content of the obtained powders were investigated. The spherical Ni–Ti composite powder with a slightly Ti-rich composition was obtained at the optimal feeding rate of 35 g/min and carrier gas flow rate of 3 L/min. In addition to NiTi phase, elemental Ni and Ti powders were also identified in the produced powder. The prepared powder was adopted for laser powder bed fusion densification. Microcracks and pores were observed in the L-PBF-processed samples. In addition to NiTi main phase, un-melted elemental powders, Ti2Ni and Ni3Ti phases were found in the microstructure of the printed parts. Based on the DSC analysis, the transformation temperatures of austenitic NiTi to martensite and vice versa were determined.