HIGH-TEMPERATURE DUCTILITY OF N65M TYPE CORROSION-RESISTANT ALLOY MELTED IN VARIOUS WAYS

The influence of various deoxidation and microalloying options on the high-temperature ductility and structure of the N65M type corrosion re sistant alloy melted in various ways has been examined It is demonstra ted that the ductility level is determined first and foremost by the g rain boundaries condition, and in many respects by the presence of har mful impurities segregation at the grain boundaries, and particularly, carbon. The latter promotes M12C type carbides precipitation in volum es at the grain boundary regions. Surfactant elements (Mg, B) added in optimum amounts attenuate grain boundary segregation by carbon, modif y the breakdown kinetics at the grain boundaries and hamper the format ion of carbide precipitates there. A combination of these effects resu lts in a change in the failure mechanism and an increase in the high-t emperature ductility by a two to threefold factor. Recommendations con cerning alloy melting procedures are made.