Phase composition and formation mechanisms of a high-velocity electric arc-sprayed FeNiCrAl coating

Abstract

FeNiCrAl coatings are wear-resistant and are applied as surface protectants for mechanical parts. The phase composition of a coating strongly impacts its performance; therefore, the internal phase composition and formation mechanisms of FeNiCrAl coatings need to be studied in detail. In this study, a FeNiCrAl coating was prepared using high-velocity arc spraying, and an X-ray diffraction (XRD) analysis of the coating revealed the coexistence of α- and γ-Fe phases, Fe-Al and Ni-Al intermetallic compounds, a Cr0.19Fe0.1Ni0.11Al0.17 solid solution phase, FeO, Fe2B and (Fe, Cr)3C. The FeNiCrAl coating microstructure and phase formation mechanisms were analysed by transmission electron microscopy. The coating consisted of many nanograins and micrograins with diameters of <50 nm and 0.1–0.2 μm, respectively. The presence of large grains indicated that restructuring and recrystallization processes occurred during the coating preparation procedure. The main coating phases included the γ-(Fe, Ni) phase, Al2O3 and Cr2O3 oxides and NiAl, Ni3Al, FeAl and Fe2Al5 intermetallic compounds. The rapid non-equilibrium solidification processes that occurred during the arc spraying process resulted in the coexistence of multiphase compounds. In addition, high-density dislocation tangles were observed in the coating. The presence of multiphase compounds and high-density dislocation tangles improved the cohesive strength and hardness of the coating.