Effectiveness of phased array focused ultrasound and active infrared thermography methods as a nondestructive testing of Ni-WC coating adhesion

ABSTRACT

The substrate/coating adhesion is a crucial parameter conditioning the quality of coating and its durability in service. For this reason, an inspection of the coating integrity, in particular, the presence of adhesion defects will be of great importance. The adhesion inspection is usually ensured by destructive methods, such as traction, interfacial indentation, four-point bending, testing scratch, etc. However, it is currently hampered by the absence of a satisfactory non-destructive method. Among the non-destructive testing technologies widely used in the industrial field, there are X-ray diffraction, ultrasonic inspection, and infrared thermography. In this paper, two methods are investigated: ultrasonic inspection, which becoming more efficient, especially with the emergence of phased array systems that allow to investigate different inspection angles and focusing depths, and the active infrared thermography. Experiments were performed on metallic coatings deposited on a mild steel substrate. Coatings were containing artificial defects (flat bottom holes with different diameters) at the interface and others were exempts of defects. Longitudinal waves with specific delay laws were generated through a phased array contact transducer (5 MHz of central frequency). Experimental results show that the ultrasonic method allows detecting and sizing defects with a diameter of 1 mm located in thick coatings.

KEYWORDS:

• Substrate/coating adhesion
• nondestructive testing
• phased array
• coating
• defects
• detection

Acknowledgments

The authors wish to thank Professor Elamrani Mostafa from Faculty of Sciences-Oujda (Morocco).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the CNRST (Morocco) and the ARES-CCD development cooperation (Belgium); Centre National pour la Recherche Scientifique et Technique;