Microstructure and mechanical behavior of mechanically alloyed ODS Ni-base superalloy for aerospace gas turbine application

Abstract

The gamma prime precipitation strengthening behavior and oxide dispersion strengthening behavior of mechanically alloyed oxide dispersion strengthened (ODS) Ni-base superalloys have been investigated. The most important microstructural feature affecting the elevated temperature strength of ODS alloys was found to be the grain aspect ratio. Grain aspect ratio after zone annealing was sensitively related to the primary grain size in as-extruded Ni-base superalloy. There was a suitable range of primary gain size to obtain a coarse elongated gain structure after zone annealing. The large grain aspect ratio above a critical value of about 20 resulted in an increase in stress-rupture life more than two orders of magnitude at 950 degrees C. The size and distribution of the gamma prime precipitates were dependent on the solution heat treatment conditions. The microstructural parameters on the gamma prime precipitates significantly affected on the stress-rupture property of ODS Ni-base superalloy at the intermediate temperature range.