Spray forming thick nanostructured and microstructured FeAl deposits

A thick freestanding nanostructured deposit (5 mm) was successfully synthesized by spray forming of milled Fe-40Al powder using the High Velocity Oxy-Fuel (HVOF) technique. Its microstructure was investigated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), quantitative metallography as well as microhardness. Comparison is made with the microstructure obtained in a thin (300 μm) HVOF nanostructured coating, a thick (5 mm) microstructured deposit produced by atmospheric plasma spraying (APS) from atomized powder as well as the initial feedstock powders in order to depict and discuss the effect of the processing conditions on microstructure formation and associated hardness.