An assessment of static recrystallization in L-605 Cobalt-based superalloy

Abstract

In this research, the effect of cold rolling, annealing time and temperature on microstructure and hardness were studied in L-605 superalloy. A cast bar of L-605 alloy was hot rolled at 1200 ºC. As the following, it was solutionized at 1230 ºC for 1 hour and finally was cold rolled by different amounts (i.e. 5-35 percent thickness reduction). The cold-rolled samples were heat treated for different times (i.e. 2-120 min.) at temperature range of 1068-1230 ºC in order to study their recrystallization behavior. The results of microstructural analysis indicated that static recrystallization is responsible for microstructural refinement and coarsening, so that an increase in the amounts of cold rolling resulted in a fully recrystallized microstructure at lower temperature. This analysis also indicated that annealing temperature is more effective than annealing time in grain growth. Microstructural evaluation as well as showed that carbides such as M₇C₃ and M₂₃C₆ which have been reported in some literature were not observed during rolling or annealing in this research.  It is perhaps due to usage of high annealing temperatures  or possibly due to their very low contents which was not possible for us to evaluate their formation with conventional methods. Hardness results revealed that higher annealing temperature lead to lower hardness values as expected.