Processing and characterisation of nanocrystalline iron aluminide coatingsprepared by thermal spraying of milled powders

This paper presents the first results of an ongoing research which was set up to investigate the possibility of processing an ultra fine grain Fe-40AI (Zr, B) alloy using a thermal spraying route. The coating produced here by high velocity oxy-fuel (HVOF) thermal spraying of milled powder had a high ly metastable microstructure, inherited from the initial milling, that was characterised essentially by the nanometer grain size of its FeAl phase. Th e hardness of this nanocrystalline coating was 35% higher than that of a co nventional coating obtained from atomised powder and close to that of a ful ly dense bulk material having a micrometer grain size.