....The cavity/void is presumed to have been the location of a large inclusion that likely contributed to the initiation of the failure at that point - slag?....
If this is the presumed initiation point of the failure, do these characteristic seem similar to the outer barrel adjacent to what was the braze joint?
The reason I ask is could rust, that wasn't a part of the original construction, take on the SEM appearance of "slag" and possibly run along two dissimilar materials, such as the braze and barrel? The relative sizes of the potential manganese sulfide pools and the initiation point seem to indicate that "burned" steel may not have been the primary contributor. As in the past, if there was a partially, if not completely, successful braze joint, could there have been a manufacturing error in that area, that could've been hot enough to burn steel? Only thoughts.
