Scientists of the Moscow Power Engineering Institute, the Federal Research Center of Krasnoyarsk and the Moscow Automobile and the Road Construction State Technical University have developed a technology to increase the surface hardness and wear resistance of steel products.
The researchers found that laser processing and making surface layers strengthened with nanocarbon materials enhance the hardness of the modified material by over five times as compared to the most common technical steel. The results of the research work are published in the journal Physics of Metals and Metallography.
Surface reinforcement of steel makes it possible to increase the strength and operational properties of machine parts and tools operating under wear and contact loads. Usually, in order to change the physical or chemical properties of the material, they apply the technology of alloying, i.e. adding impurities to steel. This method can be substantially improved by using nanocarbon materials such as fullerene, graphene or nanocarbon tubes, along with a surface treatment laser.
According to Grigory Churilov, Dr.Sci.Tech., the Head of the Analytical Methods Laboratory for Investigating Substances at the Physics Institute, the advantage of the laser method is the possibility of contactless, fast and strictly dosed transfer of energy to the treated metal surface.
Russian scientists tested how the power of laser radiation affects the hardness of the surface and the friction factor of technical iron modified with nanocarbon. As a nanomaterial, soot was used, which is obtained by the production of fullerenes in an arc discharge with graphite electrodes.
Scientists have managed to select such capacities, in which the metal surface does not melt and at the same time there is a significant increase in its strength. As a rule, the hardness of the material was maximal at the center of the laser beam impact zone and decreased toward the edges. The non-homogeneous distribution of hardness increased the wear resistance of the surface, since a metal alloy made from a soft base and hard inclusions had a lower friction factor. After laser treatment, the hardness of iron coated with nanostructured carbon increased more than fivefold in comparison with the most common technical steel. The friction factor of the reinforced material turned out to be 20-30 percent less than that of the initial samples of technical iron under conditions of dry contact of the surfaces. Along with nanocarbon soot, other types of nanocarbon materials, such as fullerenes and graphene oxide, were used to harden the steel surface. To treat the surface with a nanocarbon coating, not only laser radiation, but also a beam of fast electrons was used. The maximum hardening effect (up to 8 times) was observed in the case of using fullerenes with subsequent laser treatment, and the largest depth of the hardened layer was obtained as a result of surface treatment with an electron beam.
“The hardness and wear resistance of steels, especially those containing carbon, nitrogen or boron compounds, are significantly improved after laser treatment. In addition, laser heating does not cause deformation of products”, - Alexander Eletsky, Dr. Sc., a research associate of the Moscow Power Engineering Institute explained.
The study is financially supported with a grant from the Russian Science Foundation.