The Influence of Grain Boundary Phosphorus Concentration on Liquid Metal and Hydrogen Embrittlement of Monel 400

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Department of Materials Science and Engineering


The susceptibility of Monel 400® to embrittlement by mercury and by hydrogen was measured as affected by thermal treatment. Specimens were annealed at 900°C and either quenched or furnace cooled. Auger analysis revealed phosphorus segregated to the grain boundaries; furnace cooling causes the boundary concentration to be about twice that of the quenched material. Tensile tests were conducted with specimens (1) in air, (2) coated with mercury, or (3) cathodically precharged with hydrogen. Fractures in air were completely ductile, and ductility was not affected by thermal treatment. Fractures of mercury-coated and hydrogen-charged samples were brittle and intergranular; elongation to fracture increased significantly with increasing concentration of grain boundary phosphorus. The results are discussed in terms of additive and interactive mechanisms.

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© 1982 American Society for Metals and the Metallurgical Society of AIME. Publisher’s version of record: https://doi.org/10.1007/BF02644426

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Metallurgical Transactions A