Microstructural investigation of Fe-Cr-Nb-B amorphousanocrystalline coating produced by HVOF

摘要

Protective coatings of the steel tubes used in the oil and petrochemical industry require good corrosion and wear resistance. Our previous research shows that the Fe-Cr-Nb-B quaternary system is a promising candidate for the above application. In the current work, a new Fe-Cr-Nb-B glassy alloy, with nominal composition Fe57Cr9Nb13B21, was used to produce amorphousanocrystalline coatings by High-Velocity Oxygen Fuel (HVOF) thermal spray process onto 410 stainless steel substrate. The composition was designed to induce, during coating production, preferential formation of fine Nb-rich phases embedded within an amorphous matrix. Amorphous broad halo as well as crystalline (Fe, Cr) NbB and (Fe, Cr, Nb)(3)B-2 peaks were confirmed by X-Ray diffraction (XRD) patterns and fine micrometric Nb-rich phases with the size ranging from about 1 mu m to 100 nm were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Large fraction of Nb-rich nanocrystals was revealed by high-angle annular dark field (HAADF) and elemental mapping. Some alpha-Fe, FeB and Fe2B nanoparticles were also detected by XRD and TEM analyses. Due to the composite structure, the coating was found to exhibit much better wear resistance and higher hardness than the 410 stainless steel substrate. (C) 2016 Elsevier Ltd. All rights reserved.