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Effects of Thermal and Thermo-Mechanical Treatments on the Mechanical Properties of Centrifugally Cast Alloy 718
Final rept. Jul 1984-Mar 1987
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
The ability of thermal and thermo-mechanical treatments to impart improved microstructural and mechanical properties to nickel-base engine components has been investigated for centrifugally cast alloy 718. The effects of hot isostatic pressing HIP or thermal homogenizing treatments on the tensile, creep and fatigue properties of cast alloy 718 were evaluated at 427, 538, and 649 deg C. The results indicated that either HIP or thermal homogenizing processing of the as-cast alloy, followed by an aging treatment, produced improved fatigue crack propagation resistance when compared on the basis of stress intensity factor range. Creep life and ductility were reduced by both processing treatments but to a lesser degree by the homogenizing treatment. The mechanical behavior of the HIP processed and homogenized material is discussed on the basis of microstructural changes produced in the as-cast alloy by the processing treatments.
APPROVED FOR PUBLIC RELEASE