Article Article
Comparison of Pulsed and Lock-In Thermography Techniques for Debond Detection in Ni-B Coatings

Nickel boron (Ni-B) is one of the most widely used coatings in the aerospace, nuclear, and chemical industries due its good corrosion and wear resistance and excellent hardness properties. An essential requisite for a good coating is minimum thickness variation and good adhesion with the substrate. Often, poor bonding quality and the presence of an unbonded region can be a cause for failure in service. In this work, pulsed and lock-in thermography techniques are tested for the evaluation of bond quality of nickel-boron coatings on AISI-grade 316L stainless steel. The results, validated with ultrasonic testing for debond detection in coating systems, showed that both thermography techniques could detect the coating debonds with differences in sizing accuracy. The theoretical aspects for different techniques, their application for debond detection, and the sizing accuracy comparison between them is discussed.


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