Nanostructures surfaces
The phase composition of the galvanic Fe-Co-Mo alloys 

I.Yu. Yermolenko, Yu.I. Sachanova, M.V. Ved’, N.D. Sakhnenko
National Technical University "Kharkov Polytechnic Institute", 2 Kyrpychova St., Kharkov-61002, Ukraine.
E-mail: kirilesha72@gmail.com 

The effect of the electrolysis regimes on the phase composition of ternary Fe-Co-Mo alloys is investigated. The Fe-Co-Mo coatings were formed onto a copper substrate from electrolyte contain iron (III) sulfate, cobalt sulfate, sodium molybdate, sodium citrate, sodium sulfate and boric acid. Electrolysis was performed at: (i) direct current (dc) mode with density i of 2–4 A∙dm–2 and (ii) unipolar pulse (pc) mode with current amplitude i of 3–5 A∙dm–2 in the on / off time range of 250 msec [1]. 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. 
The phase composition of samples of composition, at at.%: Fe31Сo31Mo38, and Fe51Сo36Mo13, and thickness of 25 μm are investigated. Lines of intermetallic Fe7Мо, Fe7Co, FeCo phases found on the Fe-Co-Mo diffraction pattern obtained by dc mode, and the absence of intermetallic of СохМоy confirm the competitive deposition of alloying metals (cobalt and molybdenum) into the alloy, as well as the competition between iron and cobalt. The coatings of different composition, deposited by a direct current from various electrolytes, have the same phase composition. But the coherent scatter plot is diminished for coatings with a high molybdenum content from 66 Å to 53 Å. It is obvious that the alloy amorphization occurs due to an increase in the refractory metal content, and the change in the ratio of metals contributes the ratio of different composition phases, which will affect on the coating properties. The X-ray patterns of Fe-Co-Mo coating obtained by pulse mode, visualize lines corresponding to metallic cobalt and molybdenum, but the lines of intermetallic iron compounds with cobalt are disappearing. It has been established that the change in the phase composition under the action of a pulsed current promotes the improvement of the microhardness of Fe-Co-Mo 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. 
2. Yermolenko I.Yu., Ved’ M.V., Sakhnenko M.D., Shipkova I.G., Zyubanova S.I. Nanostructured magnetic films based on iron with refractory metals. // Journal of Magnetism and Magnetic Materials.-2019.-475.-P. 115-120.