In-depth characterization of as-deposited and annealed Fe-Wcoatings electrodeposited from glycolate-citrate plating bath

Fe-W coatings with 4, 16 and 24 at.% of W were electrodeposited under galvanostatic conditions from anew environmental friendly Fe(III)-based glycolate-citrate bath. This work aims to find correlationsbetween composition including the light elements, internal structure of the electrodeposited Fe-Walloysand functional properties of material. The obtained alloys were characterized by Glow Discharge OpticalEmission Spectrometry (GD-OES), Scanning Electron Microscopy (SEM) with Energy Dispersive X-raySpectroscopy (EDS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). Compositionaldepth profiles of 10 mm thick coatings obtained by GD-OES show that the distribution of metals isuniform along the entire film thickness, while SEM imaging depicted the presence of cracks and O- andW-rich areas inside the Fe-Wcoating with 4 at.% W. In the samples with 16 and 24 at.% of W, oxygen andhydrogen are present mostly at the surface about 1 mm from the top while traces of carbon aredistributed within the entire coatings. With increasing W content, the structure of the coatings changesfrom nanocrystalline to amorphous which was shown by XRD and TEM analysis. Also, the surface ofcoatings becomes smoother and brighter, that was explained based on the local adsorption of intermediatescontaining iron and tungsten species. Annealing experiments coupled with XRD analysisshow that the thermal stability of Fe-W alloys increases when the W content increases, i.e. the coatingwith 24 at.% W retains the amorphous structure up to 600 C, where a partially recrystallized structurewas observed. Upon recrystallization of the amorphous samples the following crystalline phases areformed: a-Fe, Fe2W, Fe3W3C, Fe6W6C, and FeWO4. Hence, the Fe-W coatings with higher W content(>25 at.%) can be considered as suitable material for high temperature applications