EFFECT OF VARIOUS ANNEALING CYCLES ON INCONEL 718 MICROSTRUCTURE
MCDONNELL AIRCRAFT CORP ST LOUIS MO
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Metallographic studies were performed to investigate the effect of various annealing cycles on grain size and precipitate morphology in Inconel 718 nickel chromium alloy. Before and after aging, the DPH hardness of all material was determined and photomicrographs at 250X and 2000X were prepared. Annealing temperatures of 1500 and 1600F failed to produce satisfactory results. Annealing between 1700 and 1800F adequately dissolves precipitated phases so that subsequent aging produces maximum hardness. Annealing overaged material at 1900F for 15 minutes appears to completely dissolve precipitate phases without altering precipitation behavior during subsequent aging or encouraging excessive grain growth. When annealed at temperatures greater than 1900F, excessive grain growth can be expected. Precipitation behavior during subsequent aging also appears different with grain boundary films forming.
- Metallurgy and Metallography