February 2025 Volume 7

EQUIPMENT & TECHNOLOGY

N-RAY IMAGING: THE MISSING LINK IN QUALITY ASSURANCE By Gregory J. Weaver

I n manufacturing, what you can't see can hurt you. When a major aerospace manufacturer recently discovered surface defects in critical dense metal components, their standard quality assurance toolkit -- including ultrasonic testing, eddy current, magnetic particle inspection, and X-ray radiography – couldn't fully characterize the problem. The breakthrough came from an unexpected source: neutron radiography, combined with an innovative contrast enhancement technique, revealed the full extent of previously hard-to-detect surface cracks. This discovery prompted a comprehensive review of their inspection protocols for similar components. Quality assurance professionals in forging and other heavy manu facturing sectors face persistent challenges when inspecting dense metal components. Traditional NDT methods each have their limitations: X-rays struggle to penetrate thick materials effectively, ultrasonic testing can miss subtle surface defects, eddy current has limitations with geometry, and magnetic particle inspection only reveals surface and near-surface discontinuities. These limitations can create concerning gaps in inspection capabilities - gaps that could mean the difference between detecting a critical flaw and possibly missing it entirely. That's where neutron radiography (N-ray) steps in to fill these crucial gaps in inspection capabilities. While not a replacement for traditional methods, N-ray offers unique advantages that comple ment existing NDT techniques, particularly when examining dense metals or identifying subtle defects that other methods might miss. How N-Ray Works Think of N-ray as X-ray's complementary cousin. X-rays struggle to penetrate dense metals - the denser the material, the harder it becomes to get acceptable images. Neutrons flip this relationship on its head. Neutrons often pass easily through dense metals, but can be absorbed by lighter elements. This equates to N-ray being highly sensitive to these lighter elements. This unique property makes N-ray particularly valuable for specific quality assurance applications where traditional methods fall short. We see this difference regularly in our inspection work at Phoenix Neutron Imaging. When examining a batch of turbine blades using X-rays, the dense metal alloy makes it nearly impossible to detect internal ceramic manufacturing residue. The same batch under N-ray imaging and with the addition of a gadolinium-based contrast agent, can allow the defect to light up like a Christmas tree.

Gadolinium-tagged turbine blade shows highlighted ceramic core material in netron image that is invisible to x-ray. Digital Advantages in Modern Inspection Modern digital neutron imaging systems are looking to trans form quality inspection capabilities. Rather than using traditional film techniques, Phoenix is developing digital solutions for its customers. These digital solutions will provide real-time feedback and allow inspectors to optimize settings rapidly, ensuring they capture the best possible view of critical features and potential defects. Neutron computed tomography software further enhances the digital capabilities and creates detailed three-dimensional models of inspected components. These systems can flag potential defects and verify measurements against specifications, improving both efficiency and consistency in the inspection process. The digital platform also revolutionizes how inspection data is handled. Results are automatically archived in secure, searchable formats, creating a comprehensive digital record of component quality throughout its lifecycle. When questions arise about part integrity, quality teams can instantly share findings with engi neering teams across locations, enabling rapid, informed decision making. Where N-Ray Shines Returning to our opening example of detecting surface defects in dense metal components, the successful use of modified gado linium tagging techniques demonstrates one of Phoenix’s N-ray's key strengths. By adapting the contrast enhancement process, inspectors were able to reveal and categorize surface cracking that far exceeded traditional methods.

FIA MAGAZINE | FEBRUARY 2025 18