Abstracts Book - IMRC 2018

• SE4-P028
INFLUENCE OF RARE EARTH ADDITIONS AND HEAT TREATMENTS
ON THE MICROSTRUCTURE OF THE INCONEL 718 ALLOY
Luis Enrique González Abarca 1 , Arnoldo Bedolla Jacuinde 1 , Alberto Ruiz 1
1 Universidad Michoacana de San Nicolás de Hidalgo, Metalurgia y Materiales, Mexico.
The superalloy INCONEL 718 is a widely used material in many fields such as
aerospace and turbine components due to its high mechanical strength, good
fatigue and creep resistance, as well as good corrosion resistance and ability to
operate continuously at elevated temperatures.
The microstructure of as-cast Inconel 718 alloy consists of primary g, laves
(Ni 2 Nb) and carbides (TiC). The influence of homogenization heat treatment,
thermomechanical behavior, solution and aging heat treatments on the
microstructure and mechanical properties of this alloy have been investigated
for an Inconel 718 with addition of 0.3% rare earths alloy (mischmetal, 48Ce,
25La, 17Nd, 5Pr, 5Fe).
The results show the solidification sequence to be LèTiCègèlaves. and that laves
being a brittle phase promotes crack propagation during the thermomechanical
processing. A homogenization heat treatment eliminates almost all of this phase
before the thermomechanical processing and a solution and aging treatment
contributed to a grain refinement.
Rare earth elements had an effect of increasing the amount of the Laves phase
due to its segregation effect to the interdendritic regions. It is also expected rare
earth to form some compounds at the grain boundaries and these in turn help
to improve the creep behavior. These results are explained in terms of the
segregation effect of the rare earth elements.
Keywords: Inconel 718, rare earth, Heat Treatment
Presenting authors email: lenrique_ga@hotmail.com