Saphyan P. Formation of structure and corrosion resistance properties of the surface layer of tubes for special purposes made from austenite steel by steam and plasma discharge treatment.

The thesis is directed: on the creation of a favorable structure, increase of corrosion resistance, change in phase composition of the surface layer of tubes made from corrosion-resistant austenite steels during their treatment by steam and plasma discharge. Regularities of the influence of steam and plasma discharge parameters on the change of phase composition, dimension of carbides and Ti(C,N) of titanium in the surface layer of tubes made of corrosion-resistant austenite steels were experimentally investigated and defined. The influence of discharge parameters on the properties such as corrosion-resistance, roughness, micro hardness and average grain size in the surface layer of tubes was found out. Increase of concentration of passivating and austenite-stabilized chemical elements (Cr, Ni) in the surface layer of tubes after their treatment by steam and plasma discharge was discovered in the research. The influence of linear power of steam and plasma discharge on the parameters of heating and cooling of the surface layer of steel tubes is defined by mathematic modeling. The technological process of removal of lubrication off the surface of tubes by steam and plasma discharge in "Centravis Production Ukraine" is introduced. The results of the research work are used in the educational process in the National Metallurgical Academy of Ukraine.