OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 4 2023 Introduction The structure of metallic glasses (MG), by contrast with metals, is amorphous, characterized by the presence of short-distance order and the absence of long-distance order in the arrangement of atoms, which is characteristic of the atomic structure of supercooled melts. Due to this, bulk MGs have high elasticity comparable to polymers, increased Young’s modulus [1–3]; magnetic properties [4], catalytic activity [5–7]; resistance to radiation and others. The production of bulk MGs with a thickness of more than 10 mm is currently difficult due to the requirement of high cooling rate of the material. Therefore, it is promising to apply MG coatings to impart properties to the executive surfaces of massive parts. MGs and hardening coatings formed from iron-based MG have increased hardness [8], increased wear resistance [1, 9, 10], lower friction coefficients [11], high-temperature resistance [12, 13] corrosion resistance [2, 14–16] and other properties [17, 18] compared with the substrate material. To obtain MG coatings, it is necessary to achieve high melt cooling rates. FeWCrMoBC composition contains elements with significantly different atomic radii, due to this melt has high viscosity, which makes it difficult to move atoms to build the crystal structure, and therefore does not require extremely high cooling rates for the formation of MG by contrast with pure metals. Electric discharge alloying (EDA) provides sufficiently high cooling rates (105–107 K/s) [19, 20] of such materials in the melt micro-bath to fix the amorphous state. EDA is based on the phenomenon of polar transfer of material from anode to cathode during the flow of microsecond low-voltage electrical discharges [21]. As a consequence, EDA can utilize a crystalline electrode-anode for one-step deposition of an amorphous coating [22]. Previously, we obtained similar coatings using electrodes (anodes) prepared by powder metallurgy. The purpose of this work is a one-stage deposition of an amorphous coating by EDA using crystalline anode material FeWCrMoBC prepared by casting with a higher iron concentration and the investigation of wettability, high-temperature resistance and tribological properties of coatings. Research methods In laboratory conditions of KHFIC IM FEB RAS the electrode material of Fe31W10Cr22Mo7B12C18 composition from a mixture of powders was created by casting method (table 1). The powders were mixed and poured into a corundum crucible, which was placed in a muffle furnace and heated up 1,200 °C. After soaking for 15 minutes, the crucible was removed from the furnace and the melt was poured onto a steel plate at room temperature. The obtained material was cut into 4×4×30 mm3 rectangles, which served as electrodes. Ta b l e 1 Composition of the powder mixture for the anode preparation Concentration, wt.% B4C W Mo Fe Cr C 2.97 32.82 11.4 29.8 19.95 3.06 The power pulse generator was used during EDA with discharge current 195±10 A; voltage 40±5 V and the following processing modes (table 2), where: D = 1/S is a duty cycle; S = T/τ is a pulse on-off time; T is a pulse period; τ is a pulse duration. The coatings were deposited on the surface of the cathode specimens made of Steel 35 in the form of a cylinder with a height of 5 mm and a diameter of 12 mm during 6 min/cm2 in air. The values of anode erosion and cathode weight gain were determined with using electronic scales BSM-120 with an accuracy of 0.1 mg. An X-ray diffractometer “DRON-7” in Cu-Kα radiation was used to study the structure of the specimens. The hardness of the coatings was measured on a PMT-3M microhardness tester at a load of 0.5 N using the Vickers method. Wear resistance and coefficient of friction of coatings were investigated according to
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