Comparative Study on the Microstructure and Wear Resistance of Two FeCr - Based High Velocity Arc - Sprayed Coatings

Abstract

Based on the wear resistance application scenarios of the heat surface tubes, fans and other components of popwer station boiler, coatings were prepared on the substrate 20G steel by high velocity arc - spraying technology with the application of two kinds of FeCr - based coating materials containing different carbon and rare earth element contents. Subsequently, the microscopic morphology and phase composition of the coatings were characterized through optical microscope (OM), scanning electron microscope (SEM), X - ray diffractometer (XRD) and white light interferometer system, and the mechanical and wear resistance properties of the coatings were tested through Vickers microhardness, tensile bonding strength, ball - disk friction and wear tests. Results showed that the microstructure of these two coatings was a typical lamellar structure. As B, C and other hard phase elements were distributed in FeCr solid solution, the microhardness of the coatings was much higher than that of the substrate. Furthermore, the high carbon content and the addition of rare earth elements contributed to a decrease of the porosity of the coatings from 2.22±0.47% to 0.92±0.13%, an increase of the microhardness from 8.05±0.53 GPa to 10.47±0.68 GPa, and a reduction of the wear weight loss by 40%. Judging from the wear morphology of the coatings, high microhardness and low porosity made the wear mechanism changed from adhesive wear to abrasive wear. In general, applying FeCr - based coatings to protect the wear surfaces could effectively solve the wear problem of the boiler parts of the power station, and thus ensure the safe and stable operation of the boiler units.

Keywords

• high velocity arc - spraying|fecr - based coating|microstructure|mechanical properties|wear resistance