Ni-superalloys are well known for their high strength, outstanding corrosion resistance and their resistance to both fatigue and creep, As a result, they are frequently used in gas-turbine and aero-engine applications. Inconel 625 also has a high resistance to chloride-ion stress-corrosion and is used in very aggressive environments. The strength of Inconel 625 is derived from the stiffening effect of molybdenum and niobium on its nickel-chromium matrix; thus precipitation-hardening treatments are not required. Control of the microstructure is very important with respect to the mechanical properties of the material. The microstructure changes during the hot rolling of the Inconel nickel-chromium superalloy 625 were investigated using FEG SEM. A detailed insight into the recrystallization behaviour during hot rolling was provided by an EBSD analysis (Figure 1). During the hot rolling the recrystallization starts on the grain boundaries, followed by the twin grain boundaries and, at even higher stresses, the recrystallization occurs on the (TiNb)CN phases inside the crystal grains. The EDS and EBSD results were able to explain the complex nature of the (TiNb)CN phases.

Figures:

EBSD IPF-Z micrograph showing microstructure development after second pass of hot rolling

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EMC Abstracts - https://emc-proceedings.com/abstract/ebsd-analysis-of-the-microstructural-evolution-of-ni-superalloys/