Flaw detection on Inconel600® using separation of single and multiple scattering contributions

Flaw detection using ultrasonic non destructive testing on coarse grain steels commonly found in nuclear power plants is disturbed by a high backscattered noise. This leads to a decrease of the detection capabilities of common ultrasonic testing techniques, particularly at high frequencies and large depths for which multiple scattering dominates. Recent studies have shown that the contribution of single scattering could be extracted from multiple scattering in complex medium. These results were obtained on a model random medium made of parallel steel rods immersed in water. They showed that the ability to detect a target could be significantly increased using a specific filtering method, based on matrix properties, in supplement with the D.O.R.T. method. In this work, this new method is now applied to real materials. Experimental results on a nickel based alloy (Inconel600®) mock-up exhibiting manufactured flaws are presented and compared to other detection techniques. The experimental set-up uses a 64-element ultrasonic array, around 3 MHz. Despite a high backscattering noise due to multiple scattering, the first results show a dramatic improvement of the detection performances.