Synthesis of B2-RuAl coatings on mild steel by laser cladding

Because of its outstanding thermodynamic, chemical and mechanical properties, ruthenium aluminide has often been reported to be an interesting candidate for future applications. In this work, powder mixtures of ruthenium and aluminium were laser cladded on mild steel using a 500 W diode laser. The quality of the coatings depends strongly on the parameters used during the laser processing. The phases and microstructures of the resulting coatings were thoroughly investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and atom probe tomography. It was found that the coatings consist of a mixture of B2-RuAl with a high amount of iron as substitutional element and α-Fe. When superimposing several layers, the fraction of α-phase in the top layer decreases significantly with every additional layer. This is a potential method for coating structures for high-temperature applications and rapid prototyping single-phase RuAl components which are difficult to achieve by conventional methods.