Obrabotka Metallov. 2017 no. 2(75)

ОБРАБОТКА МЕТАЛЛОВ № 2 (75) 2017 64 МАТЕРИАЛОВЕДЕНИЕ H. Tanei, K. Ushioda, M. Maeda, Y. Abe // ISIJ In- ternational. – 2012. – Vol. 52, N 9. – P. 1644–1648. – doi: 10.2355/isijinternational.52.1644. 23. Теория и технология азотирования / Ю.М. Лахтин, Я.Д. Коган, Г.-И. Шпис, З. Бемер. – М.: Металлургия, 1991. – 320 с. 24. Belashova I.S., Shashkov A.O. Kinetics of growth of the diffusion layer in nitriding by the thermogaso- cyclic method // Metal Science and Heat Treatment. – 2012. – Vol. 54, iss. 5. – P. 315–319. – doi: 10.1007/ s11041-012-9504-5. OBRABOTKAMETALLOV (METAL WORKING AND MATERIAL SCIENCE) N 2 (75), April – June 2017, Pages 55–66 Effect of a continuous and gas-cyclic plasma nitriding on the quality of nanostructured austenitic stainless steel Makarov A. V. 1, 2 , D.Sc. (Engineering), Senior Researcher, Head of department, Head of laboratory, e-mail: av-mak@yandex.ru Gavrilov N. V. 3 , Corresponding member of RAS, D.Sc. (Engineering), Head of laboratory, e-mail: gavrilov@iep.uran.ru Samoylova G.V. 1 , Ph.D. student, e-mail: a1isova@mail.ru Mamaev A. S. 3 , Ph.D. (Engineering), Researcher, e-mail: asm@iep.uran.ru Osintseva A.L. 2 , Ph.D. (Engineering), Senior Researcher, e-mail: lkm@imach.uran.ru Savrai R.A. 2 , Ph.D. (Engineering), Head of laboratory, e-mail: ras@imach.uran.ru 1 M.N. Miheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, 18 S. Kovalevskoy st., Ekaterinburg, 620990, Russian Federation 2 Institute of Engineering Science Ural Branch of RussianAcademy of Sciences, 34 Komsomolskaya str., Ekaterinburg, 630049, Russian Federation 3 Institute of Electrophysics of the Ural Branch of the RussianAcademy of Sciences, 106Amundsen St., Ekaterinburg, 620016, Russian Federation Abstract Plasma nitriding is an effective method of the austenitic stainless chromium-nickel steels hardening. Usage of the low-energy electron beams (to 1 keV), that is typical for plasma generator, provides smaller loss of energy then usage of gas discharges. Low-energy electron beams allow change current density and ion energy independently of one another without using additional external heating devices. The lack of ion-plasma nitriding is deterioration of nitrided surface quality. Nanostructured deformation processing could be applied before nitriding with the aim of increasing growth rate of nitrided layer and reduction of nitrided surface roughness. In the paper, the influence of combined processing including nanostructuring frictional treatment by sliding indentor and following continuous and gas-cyclic plasma nitriding in electron-beam plasma at a temperature of 450 °С and 500 °С on hardening and surface quality of austenitic steel AISI 321 (0.04 wt.% С; 16,77 wt.% Cr; 8.44 wt.% Ni; 1,15 wt.% Mn; 0,67 wt.% Si; 0,32 wt.% Ti; 0,31 wt.% Cu; 0,26 wt.% Mo; 0,12 wt.% Co; 0,12 wt.% V; 0,04 wt.% P; 0,03 wt.% Nb; 0,005 wt.% S; and Fe for balance) is studied. It is established that friction treatment leads to occurrence of 95 vol. % α´ strain-induced martensite and increas- ing of microhardness to 780 HV 0.025 on nitrided surface. On the nanostructured by frictional treatment surface of metastable austenitic steel AISI 321 (in contrast to nitrided coarse-grained steel) after continuous plasma nitriding in electron-beam plasma pore formation and intensive blistering is observed. Blistering is characterized by forming of steam blows and surface blowout. Obvious blistering appears due to advanced nitrogen diffusion into nanostructured surface with α´ stain-induced martensitic structure. Improvement in quality of the nitrided steel surface, hardened by frictional treatment (decreasing of blistering, pore formation and roughness), is achieved by means of: 1) gas-cyclic plasma nitriding is carried out at the conditions of periodic alternation nitriding semicycles in mixture of argon and nitrogen and denitriding (without nitrogen sup- ply); 2) nitriding temperature decreasing from 500 °С to 450 °С. However after gas-cyclic plasma nitriding of nano-