Aluminide coatings formed on Fe-13Cr steel at low temperature and its oxidation resistance

A novel aluminizing process has been developed to produce aluminide coatings on Fe-13Cr stainless steel at a much lower temperature (520-600 degrees C) and with a shorter time (60-240 min) compared to the conventional pack-aluminizing processes. In this process, chemical reaction and atomic diffusion were accelerated by ball impact generated by mechanical vibration. The effects of operation temperature and duration on the coating thickness were studied. Scanning-electron microscopy (SEM and EDS) showed that the coatings appeared to be dense, homogeneous, free of porosity and with excellent adherence to the substrate. X-ray diffraction (XRD) analyses indicated that the coatings consisted mainly of eta-Fe2Al5 and theta-FeAl3. High-temperature oxidation tests were carried out in air at 900 degrees C. The results indicated that the aluminide coatings obtained from this process have significantly improved high-temperature oxidation resistance.