Study of Diffusion, Kinetics of Sintering, Structure and Properties in Powder Steels with Free and Spark Plasma Sintering

The diffusion processes and sintering kinetics in micro- and nanodispersed "Fe-Ni" powder systems during sintering in α- and γ-regions with free and spark plasma sintering (SPS), as well as the structure and properties of metastable powder steels on the basis of these systems are studied. The diffusion coefficient ( D ) in iron-nickel systems was 2-3 times higher in systems with nanodispersed nickel powder than in the system with microdispersed powder. The SPS provides, at lower temperatures and a time, an increase of D by an order of magnitude or more, compared to free sintering. The coefficients of the equation of the Ivensen sintering kinetics are calculated. The use of SPS for the iron-nickel powder system significantly reduced the activation energy of sintering. In the SPS process, as in free sintering, in the carbide steels of the "iron-nickel-titanium carbide" system, a ferrite-austenite structure is formed in which, after abrasion friction, a metastable austenite is transformed into a martensite of deformation, while the volume of conversion is larger, the higher were the hardness, microhardness and wear resistance. The use of nanodispersed powders of nickel and titanium carbide for the manufacture of diamond tools have improved its cutting ability .