Re: Heat Treat certification
I don't know that I'd be able to point you to a specific area where it is listed as a requirement (I'm fairly new to quality and still trying to differentiate what things are requirements and what things are above and beyond), but I would assume this would fall under "Records of Material/Performance Test Results" much like a material cert or plating cert would.
Our general rule of thumb is we try to get a cert for every process done to a part (i.e. plating, annealing, annodizing, patching, etc.).