Materials Science

Stronger Steel

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Science  12 Aug 2005:
Vol. 309, Issue 5737, pp. 990
DOI: 10.1126/science.309.5737.990b

Ferritic and martensitic steels are preferred structural materials for use at elevated temperatures in power plants. Their major advantage is good thermal behavior relative to other elevated-temperature alloys, but they suffer from not being strong enough at high temperature. Niobium, vanadium, and nitrogen have been added to push upward this maximum-use temperature, but alloying may have reached its limit for enhancing these steels. The development of alloys that are strengthened through the dispersion of oxide particles requires expensive manufacturing techniques. Under normal processing conditions, commercial steel alloys develop large metal (M) carbon precipitates or MX particles, where X is Nb or V. Small MX precipitates confer higher-temperature stability, and Klueh et al. have developed methods to increase their density. High-temperature rolling was used to create dislocations in the alloys that acted as nucleation sites for the MX particles, increasing the nanoparticle density by three orders of magnitude. Tests on treated commercial alloys showed increases in yield stress, particularly above 620°C, which is the upper use temperature for the untreated alloys. — MSL

ScriptaMaterialia 53, 275 (2005).

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