PREPARATION OF SPHERICAL NB-16SI ALLOY POWDERS FOR ADDITIVE TECHNOLOGIES BY MECHANICAL ALLOYING AND SPHEROIDIZATION IN ELECTRIC ARC THERMAL PLASMA

Abstract

The creation of new higher melting temperature materials for gas turbine engines is one of the most important tasks of modern materials. This is due to the fact that nickel superalloys currently used for these purposes have a low melting point about 1400 °C which limits their own maximum working temperature to 1100–1150 °C. Ni alloys can be replaced by natural composites with refractory metals as a matrix and their silicides as intermetallic hardeners. Only three of refractory metal – silicon binary systems exhibit stability to the Me5Si3 silicide, namely Nb5Si3, Re5Si3 and W5Si3, Nb5Si3 is the best compound among other silicides with regard to the combination of high melting point and low density. The use of Nb–Si alloys in additive manufacturing machines is of considerable interest. The paper presents the results of experimental studies on the thermal plasma processing of Nb–16Si alloy powder prepared by mechanical alloying of Nb and Si elemental powders. Nb–16Si (at.%) alloy powder was prepared by mechanical alloying of pure element powders using the Fritsch Pulverisette 4 planetary mill. Spheroidization was carried out on a plasma unit based on vortex-stabilized arc thermal plasma generator. The results of experimental studies conducted confirmed the possibility to perform plasma spheroidization of Nb–16Si alloy powder particles obtained by mechanical alloying. It is shown that the particle surface after spheroidization is rough and reflects the cast structure of the material. Three phase components having different optical contrast are revealed on microsections: Nb5Si3, Nb3Si and Nbss, which is confirmed by X-ray diffraction.