david weaver
The method that bill is talking about has actually been used elsewhere, too. I saw a hard edge set of lawnmower blades on youtube last year (don't ask, my interests are varied in just about anything that involves machines or blades).

They are essentially a hard layer like this and as the steel above the layer wears, but the hard layer wears much more slowly. It looks like they work well for grass as long as there's no rocks (a strange thing to be looking at, but the idea caught my eye. I use a reel and quite like it just as it is).