INVESTIGATING THE FERRITIZATION PROCESS IN THE Fe2O3–Ni–CoO–MoO3 OXIDE SYSTEMS AND DEVELOPING A TECHNOLOGY FOR OBTAINING COMPLEX OXIDES

Abstract

In modern engineering, materials with functional properties are in great demand, especially those with high strength and ductility, where the impact strength plays a unique role as a structure-sensitive property. Some of these materials are maraging steels, which are ultra-pure alloys and are characterized by an accurate chemical composition, absence of impurities and precise structure. Obtaining these steels is possible using powders of alloyed steels and their further compaction, and that should be carried out by such technologies that would promote diffusion processes and prevent the presence of residual porosity in the structure.

It is revealed that the existing methods for obtaining alloyed powders of steels, including maraging steels, do not provide a homogeneous structure and high chemical purity, except for the method of complex oxide synthesis and subsequent reduction. The mechanism and kinetics of ferritization in the Fe₂O₃–NiO–CoO–MoO₃ oxide system have been studied. The process of synthesis of complex oxides is substantiated experimentally. On the basis of experiments carried out, an effective technology for obtaining alloyed oxide powders with a solid solution structure has been developed. By the method of reduction of complex oxides, maraging steel powders with required structure and ultrapure chemical composition are obtained. The obtained powders have high mechanical and technological properties. Based on the results of the experiments, the following modes of synthesis and production of ferrites for the Fe₂O₃-NiO-CoO-MoO₃-NH₄Cl system are selected: heating temperature - 110025⁰C, holding time – 3,5…4,0 h. It is shown that the process of ferritization proceeds in stages. First, chlorination of oxides occurs, then volumetric and

secondary reactions. The synthesis of the oxide system with the participation of NH₄Cl is carried out according to the mechanism of heterogeneous reactions both in the gas and solid phases, the products of which are complex oxides such as MeFe₂O₄, MeOFe₂(MoO₄)₃,

spinel, and NiFe₂O₄CoMoO₄ solid solutions.