Fatigue damage of the surface layers of metal is a characteristic cause of failure of rolling bearings, gears and a number of other machine parts operating under cyclically repeated contact loads. Resistivity to the development of contact damage of steels obtained by hot forging porous blanks is determined by the presence of cohesive bonds between the particles of the base powder, as well as by the presence of non-metallic inclusions and grain size. The possibility of increasing the contact endurance of hot-deformed powder steels due to micro-doping with calcium has been studied. Iron powders with various content of impurities, as well as atomized powder of low-alloyed chromium-molybdenum steel were used as the basis for preparation of the blends. Calcium was doped as calcium carbonate. Mixing was performed in a planetary centrifugal mill. Samples for mechanical testing were obtained by hot forging porous blanks. After hot forging the samples were carburized to compensate for the loss of carbon in the surface layer. It has been established that doping calcium microadditives is favourable for increasing the energy content of damage under the conditions of exposure to contact-fatigue and bending loads. This is due to a decrease in the size of austenite grains at the expense of inhibition of their growth during the adsorption of calcium at the grain boundaries. Microalloying with calcium changes the localization of seats of contact fatigue damage. In samples-witnesses without microadditives of calcium cracks originate near non-metallic inclusions of sharp-angled shape in the near-surface zone. In microalloyed specimens the cracks are located in the subsurface layer in the area of Hertz maximum shear stresses.
The technology of powder forging (PF) gained significant development after the Second World War. In 1990, almost simultaneously, two monographs were published, which examined the scientific and practical aspects of PF [1 , 2] . Kuhn and Ferguson gave a review of the studies on obtaining parts for structural purposes by PF, which were performed in North America and Europe by that time. The monograph by Kuhn and Ferguson published in English is available to a wide circle of specialists in the field of powder metallurgy (PM). Monograph by Dorofeyev Yu. G. et al. was published in Russian, which had limited readership. In this monograph experience in developing PF technology on the territory of the former Soviet Union was extended. For a variety of historical circumstances, the most significant volume of scientific and practical developments of PF was held at the Department of Materials Science and Problematic research laboratory of dynamic hot pressing of the Platov South-Russian State Polytechnic University (PSRSPU). Previously, the University was named the Novocherkassk Polytechnic Institute. Part of the works was performed in collaboration with the Institute for Problems of Materials Science (Kiev, Ukraine) [3] .
It is possible to expand the applications ranges of powder material products by enhancing the performance properties of these products in addition to their manufacturability and reliability together, it’s possible by materials structures modification. In this paper, the effect of fullerene (C60) additives to iron-based powder material has been studied. All samples produced by Hot-Forging (HF) powder materials technology. Green and HF density of the obtained samples calculated by volume / weight and Archimede’s principle, respectively. The effect of technological parameters on the microstructure of carbon steels’ samples was done by an ALTAMI MET-1M metallographic microscope. Tensile test executed by using of a universal testing machine UMM –5 and the microhardness (HV10) was measured by REICHERT hardness test machine. The results showed that the HF C60 steels’ samples had higher density and strength of 0.81 and 25%, respectively, with a good plasticity in comparison with graphite steels’ samples.
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