Try coated EMs, Tailn or Ticn. Also, bump up the chip load, double it or more. You're pre-maturely wearing down the cutter by 'rubbing' too much on the material. (Make each pass of the flute count, take as much as you can.. removes heat as well )
Carbide will work nicely, but inserts will work better, IMNSHO.
Hardmill will prolly have a say on this as well...
'Rekd