Effect of NiCr Clad BaF2•CaF2 Addition on Wear Performance of Plasma Sprayed Chromium Carbide-Nichrome Coating

NiCr clad BaF2 center dot CaF2 fluoride eutectic powders were added into chromium carbide-nichrome feedstock to improve the tribological properties of NiCr-Cr3C2 coating, and the structures, mechanical, and ball-on-disk sliding wear performance of the coating were characterized. The results show that NiCr cladding can effectively decrease the density and thermophysical difference between the feedstock components, while alleviate the decarburization and oxidization of the constituent phases, and form the coating with a uniform and dense microstructure. However, the addition of BaF2 center dot CaF2 has a negative effect on mechanical properties of the coating. When the temperature reaches 500 A degrees C, the BaF2 center dot CaF2 eutectic is soften by the heat and smeared by the counterpart, thus the low shear stress lubricating film forms between the contact surface, that improves the tribological properties dramatically. At this temperature, the dominant wear mechanisms also change from splats spallation and abrasive wear at room temperature to plastic deformation and plawing by the counterpart. Within the temperature range from 600 to 800 A degrees C, the friction coefficient, the wear rates of NiCr/Cr3C2-10% BaF2 center dot CaF2 coating and its coupled Si3N4 ball are 20%, 40%, and 75% lower than those of the NiCr/Cr3C2 coating, respectively. The NiCr/Cr3C2-BaF2 center dot CaF2 coating shows superior wear performance to the NiCr/Cr3C2 coating without lubricant additive.