Mokume-gane (in metal), is frequently done with copper and nickel. Relatively inexpensive.
Yes, my use of the word "damascus" was technically incorrect. The procedure used in making "damascus" steel is indeed lost, however forge welded layered steel is well understood.
Pattern welded steel is frequently called damascus, whereas when softer metals are used, its called mokume-gane (mokume itself is often done with colored clays).
Katana blades are properly made from steel that is many layered (of one alloy however), by the process of fold, forge weld, repeat. When done with one alloy, the layers are a little hard to discern with the naked eye, but probably because of the surface local decarburization in the forge, they are visible.
You can forge weld together two or more different alloys in layers, with a resulting increase in contrast, which can be brought out even more by etching.
The cool part, is manipulating the metal in ways that alter the pattern of the layers in three dimensions. One of the simplest patterns is the twist.
I took 7 layers of box straps (clean metal), spaced between 8 layers of carbon steel bandsaw blades, forge welded them together into a relatively square cross section, then twisted along its length, then forged out into a blade. Stock removal and forging alter the pattern into really neat shapes.
A neat scaly effect comes from forging steel cable into a blade.
Its very much like how the colors get into candy canes (or those peppermint candy rounds). At the New York Custom Knife show, I've even seen mosaic patterns such as animals or the american flag, worked into the side of a blade (these guys are -way- beyond my abilities).
The damasteel that I mentioned is made by a Swedish company which produces their own alloys from powdered metal, vacuum sintered into billets, and they then forge in the pattern themselves. A bar of billet blank for your a tatoo gun would probably run $50 or so, depending on your supplier.
Of course, there are blade makers out there, who choose the cheap way out, and just etch that pattern onto the metal . . .
BTW, if all of what you're doing is in stainless, I wouldn't put a poly coat on it. I'm not sure how well poly will stand up to an autoclave (for sterilization), but stainless (if you choose something austenitic) will be fine on its own.
As for powdered metal sprays. I always thought that field was dominated by eutectic castolin. If you -need- a certain alloy, they can be a lifesaver, but for playing around, their prices can be outrageous. OTOH, I've seen some random lots of their powders on eBay for a song. Using TIG to fuse them. Interesting, never thought of that one.