New heat resisting superalloys are found

Superalloys represent densely packed cubes of microcrystals in a disorder alloy (the image from a site www.msm.cam.ac.uk)

Japanese researchers have created superalloys on the basis of cobalt and iridium which can improve characteristics gas turbines and rocket engines. New alloys much more firmly and more refractory, than nickel superalloys used now.

The modern space technics makes very high demands to used materials. To standard requirements of ease and high durability also thermal stability frequently increases. For example, in Gas Turbine and rocket engines the temperature exceeds 1000°С, and in these conditions the material should exist not simply, and to work at extreme mechanical loadings (speed of rotation of separate details exceed 100 thousand turns a minute!).

Usual metals and alloys with such problem do not consult. They start to be softened and "creep" at temperatures, essentially smaller, than fusion temperature. There is a requirement for a new class firm, not fragile, korrozionno - and rugged, and the most important thing — heat resisting materials.

For today for these purposes nickel superalloys are used (it is possible to get acquainted with their structure and properties in article Ordered alloys: structures, phase transitions, durability, Shoe-polishes of Century G / / Coolant 1997, № 3, with. 115–123). The prefix "super" reflects here not only their outstanding characteristics, but also difficult structure. At hardening in a disorder alloy crystal cubes (see an illustration) side by side grow, and such structure leads to very high durability of a material.

But progress is relentless, the temperature grows in rocket engines every year and consequently physicists search for new connections which should come in the stead of nickel superalloys. In recent article of researchers from University Tohoku (Japan) J. Sato et al., Science, Vol. 312, No. 5770, p. 90 (7 April 2006) two new classes of the superalloys which property essentially it is better than nickel connections have been described.

Japanese have found out that superalloys on the basis of cobalt with additives of aluminium, tungsten and tantalum (in particular, Co–8,8Al–9,8W–2Ta where numbers designate percentage of additives; cobalt makes all the rest, therefore the percent is not underlined), and also on the basis of iridium (Ir–10Al–10W) possess not only more high temperatures of a softening, but also more hardness, than standard industrial nickel superalloys. Microphotos confirm, as in these cases high durability — result of dense packing microcrystals in disorder "matrix".

Transition to these alloys will allow to increase a range of working temperatures at least by one hundred degrees. But, according to authors, it not a limit. It is not excluded that on the basis of cobalt and iridium together it will be possible to create a superalloy with even more impressing characteristics.