Study on the Wear and Corrosion Resistance of CoCrFeNiTi0.8-xcBN Laser Cladding Coatings

Abstract

This work aimed to explore the effect of cBN (cubic boron nitride) content on the microstructures and wear-corrosion resistance of the CoCrFeNiTi_0.8-xcBN (x = 0, 2, 4, 6 wt.%) particle-reinforced high-entropy alloy coatings. Laser cladding technology was used to prepare the coatings on TC18 substrate. The microstructures, volume wear rates and polarization curves were characterized. The results showed that the CoCrFeNiTi_0.8-xcBN coatings had an optimal forming quality under the process parameters: laser power of 1500 W, scanning rate of 12 mm/s and overlapping rate of 60%. As the cBN content increased, plenty of TiN and TiB₂ hard particles formed in situ in the coatings, significantly improved the wear resistance. As a result, the volume wear rate of CoCrFeNiTi_0.8-6cBN was only 4.0% and 16.5% of that of TC18 substrate and CoCrFeNiTi_0.8 coating, respectively; the wear mechanism changed from adhesive wear + oxidative wear to abrasive wear + oxidative wear gradually. Moreover, CoCrFeNiTi_0.8-xcBN coatings can effectively inhibit the infiltration of corrosive media by dense organizational characteristics and the physical barrier effect of oxidation-protective films. After 480 h of neutral salt spray (NSS) test, the CoCrFeNiTi_0.8-xcBN coatings exhibited excellent corrosion resistance, both of the appearance and protection rating reached level 10. Therefore, it can be used as the wear-corrosion-resistant coating for the TC18 substrate in a NSS environment.