Modification of Material Properties 258 Pulsed Electron-Beam Melting of Cu-Steel 316 System: Evolution of Chemical Composition and Properties 1 V.P. Rotshtein, A.B. Markov*, Yu.F. Ivanov*, K.V. Karlik*, B.V. Uglov**, A.K. Kuleshov**, M.V. Novitskaya**, S.N. Dub***, Y. Pauleau****, F. Thièry****, and I.A. Shulepov***** Tomsk State Pedagogical University, 75, Komsomolsky pr., Tomsk, 634041, Russia, tel:+7 (3822)49-16-95, e-mail: rvp@lve.hcei.tsc.ru * Institute of High Current Electronics, 4, Akademichesky Av., Tomsk, 634055, Russia ** Belarussian State University, 4, F. Scoriny Pr., Minsk, 220080, Belarus *** Institute for Superhard Materials, 2, Avtozavodskaya Str., Kiev, 07070, Ukraine **** CNRS-LEMD, 25 Rue des Martyrs, Grenoble Cedex, 938042, France ***** Nuclear Physics Institute at Tomsk Polytechnic University, 2a, Lenin Pr., Tomsk, 634050, Russia Abstract – The surface morphology, chemical composition, nanohardness, and tribological prop- erties of a film (Сu)/substrate (stainless steel 316) system subjected to pulsed melting with a low- energy (20–30 keV) high-current electron beam (2– 3 µs, 2–10 J/cm 2 ) have been investigated. The film was deposited by sputtering a Cu target in the Ag plasma of a microwave discharge. To prevent the local delamination of the film due to cratering, the substrates were repeatedly pre-irradiated with 8– 10 J/cm 2 . Single pulsed melting of this system results in the formation of a diffusion layer of thickness 120–170 nm near the interface, irrespective of the energy density. In contrast, an increase in number of pulses increases the thickness of this layer. For single irradiation, the nanohardness and the average wear rate of the surface layer of thickness 0.5–1 µm, including the molten film and the diffusion layer, non- monotonically vary with energy density, reaching, respectively, a maximum and a minimum in the range of 4.3–6.3 J/cm 2 . 1. Introduction Pulsed liquid-phase mixing of film/substrate systems with intense pulsed (10 –8 –10 –6 s) electron beams is an efficient method of surface modification of materials. In experiments on binary systems with components of various solubility it has been established that this method makes it possible to form, due to fast quench- ing from melt, metastable supersaturated solid solu- tions and amorphous and nanocrystalline structures, and to synthesize metal silicides and silicon carbide [1–5]. The attention was mainly given to the investi- gation of the structure and phase formation for binary systems, while the variation of the properties of the surface layers of structural alloys by their alloying from previously deposited coating was in fact with the development of sources of microsecond low- energy (20–30 keV) high-current electron beams (LEHCEB’s) [4], prospects for successful use of the given method for modification of surface-sensitive properties of metallic materials have arisen. This paper describes the evolution of the surface morphol- ogy, chemical composition, nanohardness, and tribo- logical properties of a Сu/stainless steel 316 system (Cu/SS316) subjected to pulsed electron-beam melt- ing. This system is of interest because thin-layer cop- per coatings are used for wear protection of steels. Besides, alloying (to 3–5% Cu) of austenitic SS en- hances their corrosion resistance in hydrochloric and sulfuric acids at high temperatures and resistance to the hydrogen action at high pressures and also im- proves the stability of austenite under intense defor- mations [6]. 2. Experimental Copper films have been deposited on substrates of 3 mm thickness made of austenitic SS 316 (Fe – 16.25 Cr – 10.15 Ni – 2.17 Mo– 1.63 Mn– 0.36 Cu – 0.69 Si – 0.045 C – 0.025 P – 0.013 S; wt.%). Film deposi- tion was carried out using plasma reactor based on multipolar magnetic confinement, named as distrib- uted electron cyclotron resonance plasma reactor [7]. The thickness of films was measured by optical inter- ferometer and was equal to 512 ± 30 nm. Pulsed electron melting of the Cu/SS316 system was carried out using an LEHCEB source described elsewhere [4]. The pulse duration was 2–3 µs; the energy density was varied in the range E s = = 2–10 J/cm 2 , allowing gradual transition from the initial melting mode of the Cu film to its appreciable mixing with the substrate. The number of pulses was N = 1–5. To prevent the surface cratering of samples to be treated, the substrates were irradiated, prior to film deposition. 1 The work was supported by NATO (CLG) through Scientific Affairs Division and by CRDF Program BRHE (Project No. 016–02).