Microstructure evolution and phase identification in Ni-based superalloy bonded by transient liquid phase bonding

BOERI, ROBERTO ENRIQUE; POLISERPI, MARIANA; POLETTI, CECILIA; BUZOLIN, RICARDO; SOMMADOSSI, SILVANA

METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE

SPRINGER

Lugar: Berlin; Año: 2021 vol. 52B p. 1695 - 1707

1073-5615

This study investigates the development of the microstructure in the interconnection zone of anIN718/Al/IN718 couple obtained by the Transient Liquid Phase Bonding (TLPB) process at1000 C. The crystal structure, composition and orientation of the phases formed during joiningwere examined by SEM-EDS EBSD. The results showed that the interconnection zone is amultilayered region, constituted mainly by sigma (r), Laves and a-Cr phases and the AlNiintermetallic. The evolution of the microstructure over time shows that the topologicallyclose-packed (TCP) phases grow as columnar grains, while the AlNi phase forms exiaquiedgrains. The AlNi phase is split into two layers, Al-rich and Ni-rich, both having the same crystalstructure but different chemical composition. EBSD mapping revealed that there is no grainboundary along the split line, suggesting that splitting results from a solid-state transformationrequiring no nucleation. At longer bonding time, the AlNi phase is enriched in Ni and presentsnanoprecipitates homogeneosly dispersed. These results provide experimental data thatcontribute to the understanding of TLPB of superalloys