Influence of the duration of high energy ball milling on the microstructure and mechanical properties of a 9Cr oxide dispersion strengthened ferritic–martensitic steel

Oxide dispersion strengthened (ODS) 9Cr steel was prepared by milling atomised steel powder (Fe–0.1C–9Cr–2W–0.2Ti) with nano yttria powder in a high energy horizontal ball mill (Simoloyer CM-08) for 1, 2, 3 and 4 h. Both particle as well as crystallite sizes of milled ODS steel powder reduced with milling time reaching steady state after 3 h. The grain size of the heat treated ODS steel also reduces with milling time reaching a steady state after 3 h. Four hours of milling is sufficient to get the dispersoids of less than 5 nm in heat treated ODS steel. Both yield and tensile strengths increase with milling time up to 673 K and there is no effect of milling on the strength levels beyond 673 K.