Powder Metallurgy Progress, Vol.14 (2014), No 4 222 PREPARATION OF FERRITIC 17%Cr ODS STEEL BY MECHANICAL ALLOYING FROM PREALLOYED STEEL POWDER H. Hadraba, R. Husák, I. Kuběna, R. Bureš, M. Fáberová, M. Strečková Abstract The paper describes preparation of 17Cr-1Mo-Y 2 O 3 ODS steel by means of mechanical alloying. The composite powder was prepared from commercially available AISI 434LHC steel powder by adding 0.25 wt.% of metallic yttrium or by adding 0.25 wt.% of yttria using high-energy ball milling in planetary mill under an air and Ar atmosphere. During mechanical alloying of composite powder in air atmosphere cracking of powder particles predominated over alloying and very fine composite powder was prepared having limited formability in green state. Dense samples of 17Cr-1Mo ODS steel having uniform distribution of yttria particles of size up to 10 nm were prepared from composite powder alloyed under Ar atmosphere for 12 hours and 24 hours. The ferritic microstructure with particle size about 1 μm was prepared from powder milled for 12 hours. Distinctive plastic deformation after 24 hours of milling led to finer ferritic grain structure development having particle size about 500 nm. Keywords: ODS steel, mechanical alloying, hot rolling INTRODUCTION The iron-base superalloys, based on oxide dispersion strengthened (ODS) steels, were introduced in the end of ´70 s by INCO company for high-temperature applications [1,2]. These steels having nominal chemical composition 14-20Cr-Mo(Al)-Ti-Y 2 O 3 were developed as direct successor of 9Cr-1Mo HT91 steel and combine high-temperature strength and stability of oxide dispersion with excellent resistance to surface oxidation. These steels based either on ferritic-martensitic 9Cr or ferritic 14Cr ODS steels are nowadays under consideration as a tubing material for IV generation of fission reactors and as a structural material for developed fusion reactors. ODS steels contain small amounts (about 0.25 wt.%) of homogeneously dispersed nano-size yttria particles, to increase the creep strength of the steel [3]. Moreover, the yttrium-rich nanoparticles effectively suppress softening annealing by blocking dislocations motion at elevated temperatures [4,5]. The ODS steels are prepared from blend of atomic powders and master alloys powders in ratio of the steel by mechanical alloying process. During alloying process the composite powder consists of homogenous solid solution of starting materials is obtained subsequently high- temperature compacted to dense steel. The yttrium oxide dispersion it is possible to create either by internal oxidation from yttrium atoms distributed in the composite powder during high-temperature compaction or by des-integration of yttria particles directly added to the Hynek Hadraba, Roman Husák, Ivo Kuběna, CEITEC IPM, Institute of Physics of Materials, v.v.i.; Academy of Sciences of the Czech Republic; Brno; Czech Republic Radovan Bureš, Mária Fáberová, Magdaléna Strečková, Institute of Materials Research, Slovak Academy of Sciences, Košice, Slovak Republic