UT Inspection of Inconel Weld Cladding - Partially Mixed Zone 2

[Guest102023]

The weld overlay cladding is 4 layers (~½") of Inconel on a carbon steel substrate. In metallographic cross sections we are seeing partially mixed zones with features up to ¼ inch in dimension, greater than our acceptance criterion. Everything is vertically situated within 0.05" of the fusion line. There is no actual discontinuity.

My question is for UT experts: Since the two materials have different acoustical properties, could these metallurgical effects show up as discontinuities by UT exam?



"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[JR97]

brimstoner,

As long as there is fusion in the mixed zone you will not see it acoustically. The impedance difference between Inconel and Steel is about 3%; the reflection coefficient works out to 0.02%. That said, actual practice differs from theory. About 30 years ago I was involved in trying to ultrasonically measure the Inconel cladding thickness on steel substrate. Theory says the percent of sound reflected is the same regardless of which direction the sound is travelling (from Inconel into steel versus from steel into Inconel). When going from Inconel into steel the percent reflected was minimal, as predicted by theory. However, when going from steel into Inconel the reflection was significant, determining the clad thickness was easy when geometry allowed access to the backside of the steel. The Anisotropic nature of the Inconel prevented a large portion of the sound from crossing the boundary. Back to your question; as long as the sound is originating in pure Inconel and passing through the mixture zone then into the pure steel the reflection will be minimal and you should not have a problem. If you are passing the sound the other direction .... good luck.

JR97

 

[Guest102023]

Thanks JR97,

We are indeed examining from the Inconel clad surface, so that is the answer I was hoping for.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"