Features of the structure formation of sintered powder materials using waste metal processing of steel workpieces

Introduction. Manufacturing processes, to one degree or another, are associated with the metal waste production in the form of metal chips. The development of technologies for recycling of waste from mechanical facilities is a popular solution both from the resource saving and from an environmental points of view. Among many traditional approaches to the problem of recycling metal chips, the most interesting may be the method of using chips as one of the components in a powder material. The aim of this work is to analyze the possibility of using metalworking wastes from steel 45 (metal chips) in powder compositions based on titanium and aluminum not only as a source of iron, but also as a possible source of Fe2O3 oxide. Attention to the oxide was paid in terms of initiating reduction reactions in the powder mixture based on titanium and aluminum with the formation of the Al2O3 oxide phase to obtain a metal matrix composite. Research methods: steel chips after processing workpieces from steel 45 were additionally oxidized in water and crushed in a vibrating mill to an average particle size of 300 μm for use in powder compositions with titanium and aluminum powders. Grinded and oxidized chips were mixed with titanium and aluminum powders in various proportions in order to study its interaction with these powder components. The obtained mixtures were pressed in the form of cylindrical samples and sintered in a vacuum furnace at a temperature of 1,000 °C. The phase composition and microstructure were studied using an XRD-6000 X-ray diffractometer with CuKα – radiation and an AXIOVERT-200MAT optical microscope. Results and discussions. It is shown that after milling without coolant, steel 45 chips did not accumulate a noticeable amount of iron oxides, which required additional oxidizing procedures. The interaction of grinded oxidized chips with the components of powder mixtures is considered, and its effect on volumetric changes in compacts and structure formation of metal-matrix composites is shown. The results of optical metallography and X-ray diffraction analysis (XRD) of sintered powder compositions using oxidized ground chips of steel 45 made it possible to evaluate the ongoing processes of structure formation depending on the combination of interacting components, its mutual influence, and the prospects for obtaining composites with a dispersed oxide phase.