Optimized Microstructure and Properties of Cr3C2-NiCr Cermet Coating by HVOF/Laser Hybrid Processing

Abstract

Thermal spraying has been widely used to obtain functional surface coatings against wear or corrosion in various industrial fields. However, pores and low bonding strength are the two inevitable drawbacks for thermal-sprayed coatings. In this study, a hybrid process combining thermal spraying with laser beam irradiation was employed to solve the drawbacks. A Cr3C2-NiCr cermet coating was processed successively by high-velocity oxygen-fuel spraying and laser remelting. A fully dense remelt layer without any cracks was successfully obtained. The remelt layer was composed of fused steel base metallurgically bonded with cermet coating, showing a transverse gradient microstructure in aspects of chemical composition and grain shapes. On the top surface, chemical composition and phases from the original coating were preserved, contributing to the enhanced properties of electrochemical corrosion and wear resistance. The improvement was discussed in terms of structure densifying and homogenization. The enhanced properties by the HVOF/laser hybrid process indicate promising application in industrial fields.