Structural-gradient-materials produced by gradient temperature heat treatment for dual-property turbine disc

The microstructure–property relationship of deformed parts has been becoming very critical, especially for aerospace components. The design of manufacturing process to achieve the unique and required microstructure and property is thus critical. For turbine disc, fine microstructure is required for the bore region of the disc to provide high tension strength and fatigue resistance at low temperature (420–650 °C). The coarse microstructure is also needed for its rim region to possess the excellent rupture life and crack growth resistance at high temperature (>760 °C). A unique heat treatment method was developed to produce the gradient microstructure from the bore to the rim regions. In this study, the gradient temperature heat treatment process (GTHT) was carried out on FGH 4096 superalloys under the conditions of (1080 °C260 °C/30 min, AC) and (1140 °C300 °C/30 min, AC), and two structural-gradient-materials (SGMs) were obtained. The SGM produced by GTHT under the condition of (1080 °C260 °C/30 min, AC) has gradient microstructure from the equiaxed grains to the flatted grains. In between the equiaxed and flatted microstructures, a unique transition region is found. The dual-size gradient material was thus successfully fabricated by the GTHT process under the condition of (1140 °C300 °C/30 min, AC). The grain size of coarse microstructure is approximately 40 μm, while the grain size of fine microstructure is about 4 μm. The microstructural mechanisms of the SGMs during hot working process are identified in this research. Furthermore, the developed dual-size gradient material has potential application in dual-property turbine disc.

► Structural gradient material (SGM) has been prepared by gradient temperature heat treatment.
► The microstructural mechanisms of the SGMs during hot working processes are developed.
► SGM has potentials for the application in dual-property turbine disc.