Improving sintering kinetics and compositional homogeneity of Inconel 625 superalloy open-cell foams made by suspension impregnation method
(1. O.V. Roman Powder Metallurgy Institute, 41, Platonov str., Minsk 220005, Belarus;
2. Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, 5, pr. Lavrentieva, Novosibirsk 630090, Russia;
3. Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058, India;
4. Indian Institute of Technology Bombay, Powai, Mumbai 400076, India)
2. Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, 5, pr. Lavrentieva, Novosibirsk 630090, Russia;
3. Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058, India;
4. Indian Institute of Technology Bombay, Powai, Mumbai 400076, India)
Abstract: Open-cell Inconel 625 superalloy foams were prepared by suspension impregnation method which involves replication of pure nickel foam ligaments with a mixed powder suspension and subsequent heat treatments. The objective of the present study is to find a suitable method ensuring complete densification of the superalloy foam ligaments without using low-melting additives and achieving uniform chemical composition at moderate sintering temperatures. Foams prepared using the above methodology were evaluated for the microstructure and compositional variation across the foam ligaments by scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS). Quasi-static compressive properties of the foams were evaluated. It is shown that if elemental powders of Cr, Mo and Ni are used as additives to the superalloy powder suspension, high ligament density with uniform chemical composition conforming to the Inconel 625 specification is achieved at moderate sintering temperatures. These results are attributed to the formation of low melting eutectics and to acceleration of the diffusion kinetics due to the non-equilibrium thermodynamic conditions created by large compositional gradients in the presence of elemental powders.
Key words: superalloy foam; suspension replication; sintering; diffusion; microstructure