Inhibiting compressive and tensile instability during the forming of thin-walled nickel-based superalloy hollow turbine blades via two-stage progressive compression

Thin-walled hollow turbine blades can effectively reduce aero-engine weight and improve the thrust-to-weight ratio, but their susceptibility to compressive instability under external loads results in substantial challenges for the manufacturing. Accordingly, in this study, a two-stage progressive compression method was proposed, aiming at the forming of hollow turbine blades through rolled tubular blank. Specifically, tubular blank was initially compressed to obtain a pre-formed geometry. Low-melting-point alloy (LMPA) was then poured into the pre-formed blank to create a composite billet after solidification. After radial compression of the composite billet and melting of LMPA, hollow turbine blade was obtained. The influences of pre-compression displacement of the tubular blank ( H 0 ) and the melting point of LMPA ( T m ) on the forming defects, dimensional accuracy, and strain uniformity of GH3039 nickel-based superalloy hollow turbine blade were systemically investigated numerically and experimentally. It can be found that adjusting the fill ratio of LMPA through pre-compression leads to a transition in the circumferential stress from the tension dominated state (i.e., H 0 = 0 ∼10 mm) to the coordinated tension-compression state (i.e., H 0 = 10 ∼18 mm), and ultimately to the compression dominated state (i.e., H 0 = 18 ∼ 20 mm). An optimal pre-compression displacement is essential for the turbine blade to maintain a certain degree of circumferential stretching after filling with LMPA, and thereby the buckling instability and the inward concave defects can be suppressed as well as the excessive circumferential thinning and cracking initiation. Besides, the internal pressure of turbine blade is controlled via adjusting the T m to alleviate the strain localization. The optimal process window can be determined as: T m < 125°C and H 0 = 18 mm. This forming strategy exhibits low process control complexity and high cost-effectiveness, which can provide an innovated pathway for the manufacture of hollow turbine blades.