....metal oxides ie. corrosion and "burned" (over-heated) surface steel and filler metal. "Burned" doesn't mean "melted" ....
I think burned can mean heated enough for the carbon that forms the steel starts to burn out of the steel. It might look like the metal is sparking. The temperature that it takes for that to happen is so much higher than the likely brazing temperature that it might be difficult to find any good brazing near the area.
The lost piece, initiation point, has a random appearing shape. If it were all composed of a foundry inclusion, possibly it might have the shape of an elongated streak when the barrel was forged to length. Maybe, subsequent corrosion has something to do with this mishap. The ‘bad braze’ does seem to center around the ‘inclusion’ and extend along the barrel, the way rust might find a seam.
I think these lab folks were able to identify mill slag in some of the Damascus samples. Maybe, if the term corrosion is used it has to do with rust that was formed after the gun left the factory? Only thoughts.
