Scientists have increased hardness and wear properties of titanium’s surface

Scientists have suggested the technology that increases hardness and wear properties of titanium products. With the help of plasma electrolysis authors of the work have   formed on the surface of the material rough oxide coating, and under it – solid solution of nitrogen and carbon, that increases hardness of the sample fivefold. Then researchers have polished titanium samples in the solution of electrolyte, and thus, reduced wear of the material in 4, 7 times as far as mass is concerned. The obtained information widens the sphere of usage of titanium products in medicine, industry and energetics. Results of the research are published in Coatings.

Materials on the base on titanium are widely used in shipbuilding, non-ferrous metallurgy, atomic energetics, extraction of petroleum and gas. However, titanium products are not wear resisting enough. One of the variants of the improving of titanium is using of plasma electrolytic impregnation. By this under the influence of current on the surface of metal emerges oxide layer, and under it – compounds of nitrogen and carbon. Such processing increases wear properties of material; however, it becomes rougher, and fragile porous oxidic structures easily scale.

Scientists from Kostroma State University (Kostroma), Moscow State Technological University “STANKIN” (Moscow) and Kostroma State Agricultural Academy (Karavaevo) have offered a method that increases wear properties of surface of titanium products. Researchers have used combined treatment, that includes diffusive enrichment and polishing. Authors have shown that by temperature over 850оC oxidic layers become more porous, however roughness of such samples don’t surpass initial values. When the temperature increases the bond between basic material and oxides decreases, and oxides easily fall off during friction. By this under oxidic covering there was a formation of a solid solution of nitrogen and carbon, that increases the hardness of the sample fivefold as compared with pure titanium.

Then researchers have polished the obtained titanium samples. During polishing in solution of electrolyte around the material formed thin steam gas covering, that removes protruding fragile parts of oxidic layer. Scientists have polished samples for three minutes and decreased friction coefficient, mass wear and volume wear in 2,2,4,7 and 7,6 times correspondingly as compared with unpolished samples.

“Suggested technology smoothly works on commercially pure titanium. For solution of real tasks, you need adaptation for materials that are used in real production, in the first turn in aircraft industry, space technologies, prosthesis. We are planning to do this in the nearest future”, – tells Sergei Kusmanov, doctor of engineering, professor, director of department of mathematical and natural sciences of Kostroma State University.