Mechanical properties and microstructure of 9Cr-ODS-CLF-1 steel

Abstract

A kind of oxide dispersion strengthened (ODS) steel with addition of 0.3 % Y2O3 and 0.3 % Ti was manufactured via mechanical alloying (MA) process from CLF-1 steel raw powder that was prepared by Ar gas atomization. This 10 kg ingot of 9Cr-ODS-CLF-1 steel was obtained by hot isostatic pressing (HIP) and subsequent forging. The as-HIPed and forged 9Cr-ODS-CLF-1 steel exhibits high Vicker hardness to 384 Hv which is much higher than that of CLF-1 steel (224 Hv). The ultimate tensile strength (UTS) is about 1100 MPa with elongation of 7 % at room temperature (RT). After 90 min tempering at 1013 K, the RT elongation increased to 11 % and the ultimate tensile strength decreased to 670 MPa. The creep results showed that the minimum strain rate for 9Cr-ODS-CLF-1 steel as received and 1013 K tempered state tested at 873 K under 160 MPa were low as 1.6 × 10-8 /s and 8.42 × 10-9 /s, respectively. Typical small dispersion particles were observed in the matrix. The grains showed inhomogeneous size distribution for both the as received and the 1013 K tempering state. The method of mechanical alloying combined with HIP proved to be an effective way to strengthen CLF-1 steel in large scale.