title: Creep-strengthening of steel at high temperatures using nano-sized carbonitride dispersions.
abstract: Creep is a time-dependent mechanism of plastic deformation, which takes place in a range of materials under low stress-that is, under stresses lower than the yield stress. Metals and alloys can be designed to withstand creep at high temperatures, usually by a process called dispersion strengthening, in which fine particles are evenly distributed throughout the matrix. For example, high-temperature creep-resistant ferritic steels achieve optimal creep strength (at 923 K) through the dispersion of yttrium oxide nanoparticles. However, the oxide particles are introduced by complicated mechanical alloying techniques and, as a result, the production of large-scale industrial components is economically unfeasible. Here we report the production of a 9 per cent Cr martensitic steel dispersed with nanometre-scale carbonitride particles using conventional processing techniques. At 923 K, our dispersion-strengthened material exhibits a time-to-rupture that is increased by two orders of magnitude relative to the current strongest creep-resistant steels. This improvement in creep resistance is attributed to a mechanism of boundary pinning by the thermally stable carbonitride precipitates. The material also demonstrates enough fracture toughness. Our results should lead to improved grades of creep-resistant steels and to the economical manufacture of large-scale steel components for high-temperature applications.
authors.affiliation: Steel Research Center, and Materials Information Technology Station, National Institute for Materials Science,1-2-1 Sengen, Tsukuba 305-0047, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Taneike
authors.forename: Fujio
authors.initials: F
authors.lastname: Abe
authors.forename: Kota
authors.initials: K
authors.lastname: Sawada