Net-shape manufacturing of aircraft engine disks by roll forming and hot die forging

Roll forming is a novel technique for manufacturing aircraft engine turbine disks. This paper describes an assessment of the technical and economic viability of roll forming. The capabilities of roll forming will also be compared to those of hot die forging. It was found that there is an economic pay-off for roll forming complex, low production-volume parts of nickel and titanium alloys due to a higher material yield and less expensive tooling. Roll formed disks of high temperature nickel and titanium alloys were evaluated for dimensional control, metallurgical structure, mechanical properties, and ultrasonic characteristics. The results from complex shapes indicate that disks can be produced with uniform microstructures and excellent properties. The roll formed titanium disks possessed α–β-Ti microstructures with a mean grain size of 5–10 μm. Electron back-scattering pattern analysis and inverse pole figure analyses indicated that the disks possessed essentially no crystallographic texture. Samples machined from axial, radial, and tangential sections of disks were tested in order to evaluate any anisotropy in mechanical properties of the disks.