its difficult to answer this without getting into forging hot steel and tempering it, and that would take chapters..
i heard drill rod stock is good material and i found the supplier enco stocks it..
LINK
i been wondering about the replacement blades for portable planers, if they are as tuff as the larger plainer blades they ought to make a real hard blade , but being to hard it might be prone to breaking or chipping.. i made some hunting knives mounted in Alaskan moose horn out of the big blades and they stay sharp season to season..
i keep one ear to the ground, but i dont travel metalworker circles as much i did before i retired.. and they make discoveries in the manufacture of steel and treatments every day
there is some forms you might pick up some info from vic
but i dont have my old address handy. good luck on the hunt!