Microstructure,mechanical and tribological characteristics of plasma,detonation gun and HVOF sprayed NiCr/Cr 3 C 2 –BaF 2 .CaF 2 coatings

Abstract

The microstructure, mechanical properties and tribological behaviour of NiCr/Cr₃C₂–BaF₂.CaF₂ composite coatings prepared with atmospheric plasma spraying, detonation gun spraying (DS) and high velocity oxyfuel spraying (HVOF) technologies were systematically investigated. X-ray diffraction and transmission electron microscopy analyses showed that the main phases of the three kinds of NiCr/Cr₃C₂–BaF₂.CaF₂ coatings were mainly consistent with the designed feedstock powders. The three kinds of NiCr/Cr₃C₂–BaF₂.CaF₂ coatings have similar and high microhardness. The HVOF and DS NiCr/Cr₃C₂–BaF₂.CaF₂ coatings have lower porosity and higher adhesive strength in comparison to the plasma sprayed NiCr/Cr₃C₂–BaF₂.CaF₂ coating. The friction coefficients of the HVOF and DS coatings were lower than that of the plasma sprayed coating, and the HVOF and DS coatings showed better wear resistance. The lower friction coefficients and wear rates of the three coatings and coupled Si₃N₄ balls at elevated temperatures were attributed to the formation of a compact BaF₂.CaF₂ eutectic lubricating layer on the worn surface.