OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 3 2023 The wear resistance of the coatings was evaluated under dry reciprocating sliding friction conditions. The ball-on-flat test scheme corresponded to the ASTM G133-05 standard. Tests were performed using a Bruker UMT-2 universal friction machine. A ball made of VK-6 (WC-6Co cemented carbides) alloy with a diameter of 6.35 mm was used as a counterbody. The coatings were tested under the following parameters: the load on the counterbody was 25 N, the stroke length per cycle was 5 mm, and the total sliding distance was 100 m. Before testing, the specimens were ground and polished according to the sample preparation method for microstructural studies. The volume of worn material was determined using a Bruker Contour GT-K1 optical profilometer. Results and discussion Results of microstructural studies In the cross sections of the coated samples, several zones typical for the materials obtained by surfacing technologies can be distinguished: the surfaced layer, the heat-affected zone in the base material, and the zone of the base metal unaffected by significant heating. The thickness of the surfaced layers was about 1 mm. Dendritic structure is clearly seen in the structure of all coatings at low magnifications (fig. 1). In the coating obtained without CrB appending, the detected dendritic inhomogeneity is associated with the redistribution of elements during crystallization resulting in the enrichment of interdendritic space in manganese and nickel and the deficiency of these elements in the dendrites. However, the structure formed in this case was single-phase. A detailed analysis of the CoCrFeNiMn coating structure was performed earlier in [38]. The formation of dendritic inhomogeneity in the coatings obtained with CrB appending was accompanied by the precipitation of borides of various morphologies and compositions. It should be noted that in coatings without CrB and with 5 % CrB (hereinafter, wt. % is used, unless otherwise indicated) (fig. 1a, b), the vertical direction of the formed structure is clearly distinguished, which can be explained by a small number of crystallization centers and a high temperature gradient arising due to the predominant heat flow towards the base material. In the coatings obtained with 10–30 % CrB appending (fig. 1c–e), primary a b c d e Fig. 1. Microstructure of the specimens obtained by surfacing the powder mixtures with different CrB content: a – 0 % CrB; b – 5 % CrB; c – 10 % CrB; d – 20 % CrB; e – 30 % CrB
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