Maximizing the Glass Fraction in Iron-Based High Velocity Oxy-Fuel Coatings

Developing iron-based coatings, from glass forming alloys such as SAM2X5, which exhibit outstanding corrosion performance superior to nickel-based alloys, results in particular challenges. This is because the resulting corrosion performance of the coating depends on a complex inter-relationship between the intrinsic properties including coating chemistry with its resulting protective oxide layer, the extrinsic properties related to the macrostructure with its defects resulting from the spray process, and the microstructure where one key factor is the total level of microstructural refinement achieved. As the microstructural scale is reduced, it becomes increasingly difficult for the electrochemical system to initiate electrochemical attack. Metallic glasses, which can be considered “angstrom” scaled materials, represent the ultimate in microstructural uniformity. In this article, the influence of the feedstock powder structure on the resulting glass content in the coating will be explored, because maximizing the glass percentage is one key factor in improving corrosion performance.