Definition of synthesis parameters of ultrafine nickel powder by direct electrolysis for application in superalloy production

Abstract

The optimization of the synthesis method of ultrafine nickel powder for the production of superalloys, by means of direct electrolysis of the nickel ammine complex, has been conducted. The influence of electrolyte temperature and ammonia concentration on the electrolysis process and powder characteristics has been studied. It has been revealed that an increase in electrolyte temperature leads to a larger particle size of the powder and formation of compact metal particles. It has been determined that the maximum electrolyte temperature must not exceed 50 °С. By recording the polarization curves, it was established that an increase in ammonia concentration leads to increased polarization of nickel formation and formation of finer powder. Lowering of ammonia concentration leads to contamination of the powder with barely soluble hydroxyl compounds of nickel. Analysis of the anodic curves has revealed that the nickel anode is partly soluble. It has been discovered that the addition of Trilon B to the electrolyte has a positive effect on powder characteristics. The powder formed under optimal conditions was composed of coral-like particles with the size of 40–70 µm, which could be easily ground to their spherical components if no compact metal particles were present. High purity of the powder was confirmed by the EDX. The cathodic and anodic current yields were determined to be: 35–41 % and 5–8 % respectively.