High-resolution induction thermography for detection of micro-cracks in Ti-6Al-4V alloys

ABSTRACT

This study focuses on establishing a non-contact Non-Destructive Testing (NDT) method for detecting micro-cracks in Ti-6Al-4 V sample using the Eddy Current Thermography (ECT) technique. The study employs an induction coil for heating the sample and a thermal camera equipped with magnifying lenses to monitor surface temperature distribution. The variations in the thermal image signify the presence of defects. The efficacy of the proposed method is demonstrated through the examination of four samples featuring artificially created short notches, representing micro-cracks. These notches vary in dimensions, with notch openings approximately 20 µm, notch depths ranging from 1–10 µm, and notch lengths varying from 5 to 150 µm. The investigation explores the influence of the length and depth of short cracks on defect detection, revealing an increase in thermal contrast with both the length and width of the cracks. All notches are successfully detected using the proposed method, showcasing its applicability for real crack detection. The study concludes with the successful application of the method on a sample with actual cracks measuring less than 10 µm in width, 2 µm in depth, and a length of 100 µm.

KEYWORDS:

• Micro-cracks
• non-destructive testing
• infrared
• eddy current thermography
• high-resolution
• Ti-6Al-4V
• thermal contrast

Acknowledgements

Useful technical inputs from Mr. U.S. Gupta and Mr. Deepak Kumar of DMRL on preparation of short notches are greatefully acknowledged.

We would like to acknowledge the use of ChatGPT during the preparation of this work to enhance readability and language. Following the use of this tool/service, the authors diligently reviewed and edited the content as necessary and take full responsibility for the publication’s content. These efforts markedly improved the manuscript’s language and communication.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by CARS project by DMRL (DRDO), Kanchanbagh, Hyderabad entitled ‘Assessment and demonstration of non-destructive evaluation (NDE) techniques to characterise local microstructure and damage at notch locations for Ti-6Al-4 V’.