An Overview of Thermally Sprayed Fe-Cr-Nb-B Metallic Glass Coatings: From the Alloy Development to the Coating's Performance Against Corrosion and Wear

Fe-based bulk metallic glass (BMG) presents unique tribological and electrochemical properties. Given the inherent brittle nature and dimensional limitations of Fe-based BMGs, technological and scientific efforts are focused on their use for surface engineering solutions. Fe-based BMG coatings are promising to protect steel components operating in a wide array of hostile environments, with encouraging resistance against corrosion and wear. This article summarizes the progress of Fe-Cr-Nb-B glassy coatings in terms of alloy design, glass-forming ability, crystallization, powder production, thermally-sprayed coatings, and how the microstructural features dictate the basket of properties. The strategy for selecting the alloy composition with high glass-forming ability is discussed based on thermodynamic calculations. Two main methods are presented for feedstock powder production: gas-atomization and high-energy ball milling. Different processing routes to produce Fe-Cr-Nb-B coatings and deposits are summarized: detonation spraying, high-velocity oxygen fuel, flame spraying, non-vacuum electron beam cladding, and spray forming. The resulting phases (glassy and crystalline), microstructures, porosity levels, and hardness values are comparatively discussed and related to the corrosion and wear resistances. The final part of the work is dedicated to a new generation of Fe-based BMGs that emerged as contender to further enhance the corrosion and wear resistances. [GRAPHICS] .