Creep Resistant Materials
High temperature creep is an important phenomenon to be guarded against particularly in gas turbines for power generation and aircraft propulsion. Already described ferritic stainless steel and other stainless steels are good against creep and high temperature deterioration.
Iron brass super alloys which are modifications of austenitic stainless steel series are proprietary and manufactured only by one company. Some of the additional alloying elements in these superalloys are Co, W, Mo, V, Nb, Ti, Zr, B and Cu. These superalloys are strengthened by either strain hardening or precipitation hardening. In the strain hardening alloys advantage is taken of the fact that the recrystallisation temperature of these materials is raised to higher than 925oC due to addition of alloying constituents. Therefore, the hardening effects of straining between 650oC and 900oC are retained at service temperature which usually ranges between 650oC and 760oC. The precipitation hardened alloys are generally hardened by precipitation of carbides, nitrides or borides which are stable at high temperature and these alloys may be used between 650oC to 750oC.