Physico-Chemical nanomaterials science
Formation's features of a protective coating from the high entropy alloy AlFeNiCoCuCr by electrospark alloying
Mazanko V.F., Filatov O.V., Pavliuk D.V., Pavliuk Y.O.
Department of physics for atomic transport processes, G. V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine. 
36 Academician Vernadsky Boulevard, Kyiv-03142, Ukraine. 
E-mail: pavliuk.dmytro.kpi@gmail.com

Modern science and technology development requires the creation of novel metal materials, which are characterized by higher properties than currently used materials. Recently discovered multicomponent high entropy alloys (HEA) are among such new materials.
Some formation's features of the coating of steel St.3 by the alloy AlFeNiCoCuCr with using electrospark alloying (ESA) method are considered in this paper. The alloying was carried out at the “ELITRON-22” system using three amperage modes: 0.6 A, 1 A and 1.2 A. Then samples were subjected to mechanical shock treatment. The microhardness measurements (HV) and X-ray phase analysis were performed during investigation of coatings. The influence of the coating on the electric potential value (EMF), which appears on the metal surface during a pulsed impact of load falling from a 1,7 m height was determined.
The study showed that ESA increases HV. The sample obtained using 1st mode of alloying is characterized by HV of 3.67 GPa with ratio of this value to the initial sample is equal to 1.23. The sample obtained using 2nd mode: HV is    3.73 GPa, ratio of this value to the initial sample is 1.07. A layer of HEA was formed on the surface which allowed to increase the HV. A comparison of the microhardness values of the coatings for all three modes indicates that the coating obtained at 3rd mode (1.2 A) is characterized by maximum value of HV       (4.21 GPa). X-ray phase analysis of the initial sample showed that its basis is α-Fe.
X-ray analysis of the St.3 sample alloyed by AlFeNiCoCuCr alloy shows generation of phases with elements of the anode, cathode and the environment in the surface layer of the sample, including iron oxide.
It was found during mechanical shock treatment that EMF impulses of the initial sample St.3 and sample with coating were 4.25 mV and 2.5 mV accordingly. Therefore, the presence of HEA coating on St.3 results to decreasing the EMF value in 1.7 times.