[javadog]

I'm guessing that the color change ordinarily is a result of fretting and the color is from oxidized (very small) particles of the parent metal. Did this shaft stay together after the break?

The failure looks to have originated at the keyway. Was there a scratch or gouge in the bottom? I think I see one in the picture. I also see cracks starting to form at the corners. Was the key a bad fit in the slot?

JR