I am looking for a way to write on titanium or stainless steel without complex machinery so that one can do it with a simple pen or marker. Is there anything out there?
most metal supply companies and welding supply shops stock high temp markers for use on steels.
is this what you were after?
A Sharpie will stay on pretty well. Or are you looking for something more permanent? An engraving pen will work, but it usually looks like it was written by someone with arthritis.