Microstructure of the spray formed Vanadis 4 steel and its ultrafine structure

The as-sprayed microstructure of the Vanadis 4 steel was studied. It was observed that the as-sprayed microstructure consists of martensite, retained austenite and uniformly distributed spheroidal carbides. The Kurdiumov-Sachs crystallographic relation between martensite and retained austenite is confirmed by transmission electron microscope. No macro segregation or network carbides are found. This can be explained in terms of the rapid solidification of spray forming for microstructure refining. The steel obtained by the new processing has a uniform carbide distribution, and the average carbide size is even smaller than the equivalent in the powder metallurgical Vanadis 4 steel. It was proved that spray forming can be considered as a new and high-efficient way to replace powder metallurgy for the production of Vanadis 4 steel.