Structure and Wear Resistance of Plasma-Sprayed NiCrBSiC–TiCrC Composite Powder Coatings

The NTC20 and NTC40 composite powders were produced by conglomeration from the NiCrBSiC self-fluxing alloy with additions of 20 and 40 wt.% TiCrC, respectively, using an organic binder. Since the organic binder burnt out in the plasma spray process, components of the composite powders segregated and a certain amount (up to 15–20 vol.%) of the TiCrC particles was lost. The plasma-sprayed NTC20 and NTC40 coatings showed a heterophase lamellar structure, consisting of a nickel-base matrix in which fine chromium boride and carboboride grains (1–2 μm) and TiCrC particles (5–8 μm) were evenly distributed. Electron microprobe analysis revealed a higher content of oxides in the NTC20 and NTC40 coatings compared to the NiCrBSiC coating, which was associated with the oxidation of TiCrC particles in the plasma spray process. The introduction of TiCrC additions into the NiCrBSiC self-fluxing alloy increased porosity of the plasma-sprayed NTC20 and NTC40 coatings (up to 8%) versus the NiCrBSiC coating (5%). Wear tests of the plasma-sprayed NTC20 and NTC40 coatings were performed in dry sliding friction conditions using 65G steel as a counterface. For comparison, a plasma-sprayed coating consisting of the serial NiCrBSiC self-fluxing alloy was tested. Additions of 20 and 40 wt.% TiCrC particles to the NiCrBSiC self-fluxing alloy increased the wear resistance of the plasma-sprayed coatings by 2 to 2.3 times. As the sliding speed increased from 4 to 12 m/sec, the NiCrBSiC coating underwent catastrophic wear (I ≈ 60 μm/km), while the wear rate of the NTC20 and NTC40 coatings remained constant (I ≈ 12–22 μm/km).