OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 For coating deposition, a multi-chamber cumulative detonation spraying setup (MKDU, BSTU named after V.G. Shukhov, Russia) was employed. A distinctive feature of this setup is its dual-chamber system with a focusing lens, enabling particle velocities of up to 2,500 m/s. The system is equipped with a precision gas mixture supply unit and an automated process parameter control system. The gas mixture composition (propane-butane/oxygen/air) was set at a ratio of 13/57/30 vol. %. The process parameters were optimized based on the authors’ previous research [19–20]. Three types of powders were used as feedstock materials. The base material was the self-fluxing powder NiCrBSi alloy (PR-NKh17SR4) produced by POLEMA JSC (Russia). To prepare a composite mixture based on this self-fluxing powder, boron carbide grade F1200 manufactured by Promkhim LLC (Russia) was used. The addition of 10 wt. % boron carbide was performed by mechanical mixing in a Pulverisette 6 planetary mono-mill (Fritsch, Germany) at a rotation speed of 200 rpm for 120 minutes. The uniform distribution of boron carbide particles in the NiCrBSi alloy (PR-NKh17SR4) powder was visually confirmed by backscattered electron imaging (Fig. 1, d). As a reference material, commercial powder NiCr/WC alloy (VSNGN-85) produced by Technicord LLC (Russia) was employed. This material was selected as a typical representative of wear-resistant coatings widely used in industry. The elemental composition of the initial powders was analyzed using energydispersive spectroscopy, particle morphology was determined by electron microscopy imaging, and apparent density was measured using a graduated cylinder. The characterization results of the initial powders are presented in Table 1. Fig. 1 shows the morphology of the initial powders and prepared mixture. The samples were prepared for microstructure and corrosion properties investigation using a precision cutting machine IsoMet 5000 (Buehler, Germany) and a grinding-polishing machine MetaServ 250 (Buehler, Germany). The final polishing was performed with a 3 μm Carat diamond polishing disc (Labortek, Russia). Porosity evaluation was conducted on coating cross-sections using the SIAMS 800 hardware-software complex analyzer. The thickness of the deposited coatings was controlled with an ultrasonic thickness Ta b l e 1 Characteristics of the initial powders Material Chemical composition, wt.% Particle morphology Apparent density, g/cm3 C Cr Si B Fe W Ni NiCrBSi alloy (PR-NKh17SR4) 1.0 17.1 4.1 3.6 4.8 – bal. Spherical 4.1±0.2 NiCrBSi (PR-NKh17SR4)+ 10 wt. % B4C 3.1 15.0 3.5 11.1 4.3 – bal. Mixed spheri- cal/angular 3.9±0.2 NiCr/WC alloy (VSNGN-85) 5.3 2.5 0.6 0.55 0.4 79.8 bal. Agglomerated 7.0±0.2 a b c d Fig. 1. Micrographs of the initial powders and mixture. (a), (b), (c) SE images of B4C, NiCrBSi (PR-NKh17SR4), and NiCr/WC (VSNGN-85) powders, respectively. (d) BSE image of the NiCrBSi (PR-NKh17SR4)+10 wt. % B4C mixture
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