Nanostructured surfaces
The effect of the electrolysis regime on the phase composition 
of nanostructure Fe-Co-W coatings 
Yermolenko I.Yu., Ved’ M.V., Sakhnenko N.D.
National Technical University "Kharkov Polytechnic Institute", 2 Kyrpychova St., Kharkov-61002, Ukraine.
E-mail: kirilesha72@gmail.com 

The features of the electrolysis regimes effect on the phase composition of ternary Fe-Co-W alloys are discussed. The Fe-Co-W films were deposited onto a copper substrate from citrate iron (III) based electrolyte at: (i) direct current (dc) with density i of 3–5 A∙dm–2 and (ii) unipolar pulse current (pc) with amplitude i of 4–6 A∙dm–2 at the on / off time of 250 msec [1]. The composition of the films was determined by X-ray fluorescence method. The structure of the deposits was examined by X-ray diffraction analysis using a diffractometer (DRON-2.0) in the emission of cobalt anode and CuKα radiation. X-ray patterns were recorded in discrete mode with a step 2θ = 0.1° with the exposure at each point for 20 sec; operating voltage was 35 kV, and current 20 mA. 
The phase composition of coatings containing Iron 54 at%, Cobalt 36 at% and Tungsten 10 at% (in terms of metal) of thickness of 25 μm is investigated. The X-ray patterns of Fe-Co-W film obtained by dc show some lines of Cu-substrate, and ones corresponding to inter-metallic phases Fe7W6 and Co7W6, as well as α-Fe and cementite Fe3C. Besides, a low halo with width about 10є is detected at angles 2θ 50–60є that indicates the amorphous parts in films phase structure the coherent-scattering region size of which is of 28 nm. The diffraction spectra of films obtained by pc are characterized by the presence of additional lines that corresponds to crystalline tungsten and the inter-metallic compound Fe2W, moreover, lines of B are found. Phases Co7W6, Fe7W6, Fe2W, α-Fe and Fe3C found in Fe-Co-W deposits reflect the competition of alloying metals reduction from hetero-nuclear complexes. It has been established that the change in the phase composition at a pulsed current promotes the improvement in the microhardness of Fe-Co-W coatings [2]. 
1. Yermolenko I.Y., Ved M.V., Sakhnenko N.D., & Sachanova Y.I. Composition, Morphology, and Topography of Galvanic Coatings Fe-Co-W and Fe-Co-Mo. // Nanoscale Research Letters.-2017.-12(1).-P. 352. DOI 10.1186/s11671-017-2128-3
2. Sakhnenko M.D., Ved’ M.V., Ermolenko I.Yu., Hapon Yu.K., Kozyar M.O. Design, synthesis, and diagnostics of functional galvanic coatings made of multicomponent alloys. // Mater. Sci.-2017.-52(5).-P. 680686. DOI 10.1007/s11003-017-0009-73.