Abstract
Carbides and borides appear as minor phases in Inconel 100, although the carbon content (0.18%) is relatively high in comparison to other nickel-base superalloys. The material properties of this alloy depend on a number of interrelated microstructural parameters, including the volume fraction of γ' to γ, grain size, elemental distribution, and precipitation of carbides and borides. This study presents a characterization and a failure analysis of Inconel 100 samples loaded to fracture at 760℃ and an examination of their fractography. Chemical analysis, optical metallography, SEM and EDS were used for the characterization of the unusual areas of fracture that were found on the samples. The thermodynamic stability of TiC led to the conclusion that the possibility of creating very large, stable mono carbides, especially TiC carbide, during the production process is the reason for the short time to failure obtained in this work.
Highlights
Nickel-base superalloys are by far the preferred alloys for jet engine and gas turbine components that work at high temperature, with high and low cycle fatigue, under creep resistance and in hostile environments
Optical metallography, SEM and EDS were used for the characterization of the unusual areas of fracture that were found on the samples
As-cast samples failed after a few hours (6 hrs.), and the heat-treated samples failed after 53 hours
Summary
Nickel-base superalloys are by far the preferred alloys for jet engine and gas turbine components that work at high temperature, with high and low cycle fatigue, under creep resistance and in hostile environments These alloys are reinforced by precipitation hardening of a secondary phase in coherency with a metal matrix and by secondary phases as carbides and borides at the grain boundaries. In some alloys containing niobium, gamma double prime, γ'' is obtained, forming a Body Centered Tetragonal (BCT) Ni3Nb structure [2], which can be coherent with the gamma matrix This phase is responsible for very high strength at low to intermediate temperatures, but it is unstable at temperatures above 650 ̊C.
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