Directionally solidified (DS) superalloy blades provided the basis for substantial gains in turbine engine performance in recent decades. Now, single crystal (SX) nickel-base alloy blades can be grown directionally with interior passages for cooling air, enabling more advances in engine performance and durability SX blades are composed of single crystals oriented parallel to one another span-wise, providing optimum strength, toughness and creep resistance. Problems arise when some grains grow off-axis, decreasing the blade strength. Mal-oriented grains (MOG) at the blade surface can be detected nondestructively using current Proto NDI/E systems. However, grain recrystallization may occur on the inside of hollow blades during production or during in-service flight operations. When recrystallized grains (RX) form on the inside surface of hollow blades, they are not detectable nondestructively by current inspection systemsan especially problematic and insidious condition. Based on recent research, Proto has developed a new approach to nondestructively inspect and evaluate hollow superalloy SX turbine blades. This approach exploits transmission topography (TT), advanced x-ray diffraction (XRD), precision collimation techniques and new detector technologies, while using COTS x-ray tubes. The Proto NDI/E system for SX turbines blades will be transportable for use in laboratory, production and depot facilities.
Benefit: Proto will develop a transportable inspection system utilizing transmission topography (TT) and x-ray diffraction (XRD) technologies for nondestructively and quantitatively detecting recrystallized grains (RX) within superalloy single crystal (SX) turbine blades. This NDI/E system will enable blade casting houses, OEMs and military depots to determine whether MOG due to recrystallization has occurred during production or in-service. The basis for this proposed system is Protos Laue-based NDI/E system for detecting surface MOG. This NDI/E system has been delivered to major casting houses and establishes confidence in Protos ability to develop a system for detecting recrystallized grains (RX) within the material and adjacent to cooling air passages. Protos long-term vision is to provide the industry and military a holistic NDI/E system capable of detecting MOG both at the surface and RX within hollow SX superalloy turbine blades. The technical basis and feasibility of this new system will be demonstrated in Phase I. The more mature system to be demonstrated in Phase II will provide blade casting houses, OEMs, military researchers and DOD depots a transportable capability to detect RX/MOG internal to SX turbine blades. It will provide a reliable nondestructive means for: (1) Process control, testing and verification of MOGs in new blades; (2) Ensuring highest product quality; and; (3) Support materiel disposition decisions based on nondestructive inspections of turbine blades, both new and used resulting is substantial cost savings and improved safety.
Keywords: single crystal SX), single crystal SX), recrystallized grain (RX), nondestructive inspection/evaluation (NDI/E), mal-oriented grain (MOG), Directionally solidified (DS), x-ray diffraction (XRD)., transmission topography (TT)
