Full scale gatorizing™ of fine grain INCONEL 718

Abstract

Previous subscale work showed that commercially available fine-grained Inconel 718 billet could be successfully Gatorized at parameters that would be compatible with current forging facilities. Additional work including full scale forging trials was recommended and has subsequently been completed. Two melts from the heat used to conduct the subscale forging trials were procured and used for full scale forging trials at Pratt & Whitney's Gatorizing facility in Columbus, GA. Two forging processes were used to assess the forging characteristics of the fine grain material. Both trials were conducted as two step processes and with an intermediate "delta dumping" to promote grain refinement and superplasticity in the final forging. Based on forging stress measurements, the more successful process was the one that maximized grain refinement prior to final forging. Complete die travel was achieved together with nearly complete die fill. As forged the material exhibited an extremely uniform and homogeneous grain size and post forging heat treatment trials were then conducted to establish the microstructural response. In addition, mechanical property testing (tensile, stress rupture and fatigue) was conducted and the material exhibited properties comparable to premium quality rotor grade conventional hot die or hammer forgings.