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Description
The aerospace industry frequently employs hard coatings, such as chrome plating, on sealing areas of critical components to enhance surface durability and maintain functional tolerances. Achieving optimal coating thickness and surface finish typically requires meticulous grinding. However, this process can sometimes introduce grinding burns on the substrate material, which may or may not affect the coating itself. For ferromagnetic materials, conventional detection methods for such defects include penetrant testing and electromagnetic noise analysis using the Barkhausen effect. Recognizing the need for alternative, more efficient methods, Safran has explored the implementation of active infrared thermography combined with induction excitation, offering potential benefits in automation, digital data management, and the elimination of chemical processes.
This paper presents the collaborative efforts of Safran Landing Systems and Safran Tech in developing and industrializing a new inspection approach for detecting grinding burns under chrome plating on landing gear components. The project included the definition of requirements, the creation of suitable inspection protocols, and the execution of feasibility studies through representative specimens with artificial defects to full-scale industrial A320 sliders of main landing gear with artificial and natural defects.
The developed thermographic induction technique has proven highly effective in detecting millimeter-sized defects beneath chrome coatings with thicknesses of approximately 100 µm. Throughout a series of iterative laboratory experiments and on-site field trials, the project team refined and validated robust inspection procedures, centered around the use of a robotic cell to ensure consistency and scalability in an industrial environment.
The outcomes of this work clearly demonstrate that active thermography using inductive excitation stands out as an alternative to conventional inspection methods, such as penetrant testing and electromagnetic noise measurement (barkhausen effect), for the detection of grinding defects beneath metallic coatings. This approach enables non-contact, real-time, and fully automatable inspections, significantly enhancing both process traceability and operational safety. This innovative method represents a significant advancement in non-destructive testing for critical aeronautical components.
