As far as electro etching, it can absolutely be done on an axehead.

The best way that I've found to do it without the expensive ECM equipment is to use saltwater, an energy source and a cotton marker.

First step is to decide on a design of course. After that, use something to create a stencil of your design. I use nail polish and an old metal mechanical pencil to draw the design out. If you use nail polish, I've found it best to keep it kind of thin, like same thickness you would apply to your nails, and to give it about a minute to start drying before drawing. If it's a large design, you may want to work in stages. After the design is drawn, next you need to make an electrolytic fluid. I use salt water. Regular table salt and warm water. I've never really measured, just a good bit of salt, mostly water. Next you need a power source. I use a car battery charger set to 2a drip charge. Connect the positive terminal the steel directly, there should be no resist or tape or anything else between the steel and the positive terminal. Next I take a square of Japanese cotton. I use this simply because I have an excess of it and it gives me a nice sized brush to work with when folded up. Regular cotton balls will work fine. Make the the negative terminal never makes contact with the steel or the positive terminal. Finally, turn on the power source and dip the cotton into the salt water. The negative terminal should be touch the wet part of the cotton. Now you can start brushing the design area. Go slowly, carefully. Use a napkin or something to wipe up excess salt water from the steel, this should also help to see your progress.

Inlaying is possible, but will require a deeper etch than ECM can really provide.