This paper discusses the characteristics of inclusions resulting from various consolidation techniques and their effects on the fatigue properties of a ,typical high-strength PM superalloy, Rene' 95. The nature, origin, 'and size range of defects found in HIP, HIP t isothermally forged, extruded t isothermally forged material are described and th'eir influence on LCF behavior analyzed. Thermomechanical processing improves the LCF life considerably. The improvement is attributed to the dispersion of large defects. The LCF life of forged material is also benefited by a greater tendency toward internal fatigue initiation at crystallographic origins or initiated at smaller defects. The effects of heat treatment on the mechanical properties and microstructural features of extruded t isothermally forged materials are also investigated.

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The processing trials and evaluations which led to the use of Direct Age 718 as a commercial gas turbine aircraft engine disk material are described. Initial trials performed on pancake forgings showed that high forge reductions, low forge temperatures, and heat treatment with only an age could produce very high tensile strength in Alloy 718 without degrading needed creep and stress rupture properties.As a result, trial full-scale disks were processed using this "Direct Age" technique. More extensive mechanical property testing successfully demonstrated the potential of this material for disk applications and showed that the process window was suitable for production practice. Mechanical property results for the trial pancake and disk forgings are presented and related to microstructural characteristics and processing parameters.The best combination of tensile, creep, and low cycle fatigue properties resulted from microstructures with a uniform distribution of fine recrystallized grains and a limited amount of the delta phase precipitate. The results of investigations performed to study fatigue behavior, aging response, and heat treatment effects are also discussed.

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