Microstructure characteristics and mechanical performance of Fe-Cr-Ni-Al-Ti superalloy fabricated by powder metallurgy

Fe-Cr-Ni-Al-Ti ferritic superalloy was fabricated by hot isostatic pressing (HIP) of Fe-Cr-Ni-Al-Ti gas-atomized powders. Three types of precipitates with difference in particle size, composition and morphologies have been identified in the as-HIPed ferritic alloy. Micron-sized B2-NiAl distributed in the bulk together with L21-Ni2TiAl and Fe(Cr) sub-precipitations are the dominant precipitates. Submicron-sized B2/L21 composite precipitates with Fe(Cr)-enriched outer layer and nano-scaled single B2 particles are distributed around the micron-sized B2/ L21/ Fe(Cr) composite precipitates. After solution treatment at 1100 degrees C, various types of precipitates in as-HIPed alloy can be completely dissolved, while dense spherical B2/L21 particles are precipitated rapidly even upon water quenching. During aging at 700 degrees C, the spherical particles evolve into cuboidal morphology and then coarsen and coalesce into large plates. The loss of coherency between the particle and the matrix would produce dense dislocation network at the particle/matrix interface. The measured tensile strength of as-HIPed ferritic superalloy at 700 degrees C is up to 198 MPa with a total elongation of 47.6%, and the cracks are found to be initiated at the prior particle boundaries, which leads to the failure. To fabricate the high-performance Fe-Cr-Ni-Al-Ti superalloy by powder metallurgy, we suggest that the prior particle boundaries should be avoided during consolidation process. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, a Fe-Cr-Ni-Al-Ti ferritic superalloy was fabricated by hot isostatic pressing (HIP) and the types and evolution of precipitates were investigated. The results showed that the precipitates could be completely dissolved during solution treatment at 1100 degrees C, while they underwent morphological evolution and coalescence after aging at 700 degrees C. The alloy exhibited high tensile strength and elongation, but failure may occur at the initiation of cracks.