The deposition of a thin (several tens of microns) protective coating in atmospheric conditions is a challenging task for surface engineering. The structural features and tribological properties of a particle-reinforced metal matrix composite coating synthesized on middle-carbon steel by air pulse-plasma treatments were studied in the present work. The 24–31 µm thick coating of “24 vol.% (TiC + WC)/Hardened steel matrix” was produced by 10 plasma pulses generated by an electro-thermal axial plasma accelerator equipped with a consumable cathode of novel design (low-carbon steel tube filled with “TiC/WC + Epoxy resin” mixture). The study included optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD, microhardness measurements, and dry “Ball-on-Plate” testing. The carbides were directly plasma-transferred to the substrate (steel of AISI 4145H grade) from the cathode without substantial melting. The hard (500–1044 HV) coating matrix consisted of 57 vol.% austenite (1.43 wt.% C) and 43 vol.% plate martensite was formed via carbon enrichment of steel from plasma flow. Additionally, a minor amount of oxide phases (TiO₂, WO₂, WO₃) were dispersed in the matrix. As compared to substrate, the coating had a lower coefficient of friction; its volumetric wear was decreased by 4.4 times when sliding against hardened steel ball and by 16 times when sliding against SiC ball.

This paper deals with the evaluation of mechanical and tribological properties of Ni-Co galvanic coatings at elevated temperatures. The coatings were deposited on the copper surface, which in practice is the material of the crystallizer. Ni-Co coatings are manufactured to increase the abrasion resistance of the crystallizer surface at elevated operating temperatures. The microhardness (HV0.05) measurements of the coating at 400 °C were used to determine its mechanical properties. The Ball-on-Disc Test was used to determine the tribological properties of the coatings at 400 °C. The mechanical and tribological properties of Ni-Co coatings at elevated temperature were compared to the results of experiments performed at room temperature. When heated to 400 °C, HV0.05 decreased by 9.5 to 22% (depending on Co content in the coating) compared to the values that were measured at 23 °C. The change in the COF for the Ni-Co coating at 400 °C was from 0.680 to 0.750 depending on the Co amount compared to the values at 23 °C. The COF values at room temperature ranged from 0.373 to 0.451. The places with higher wt. % Co had better friction properties than the places with lower wt. % Co.