8670 vs 15N20
Cousins from the same industrial family: both are band-saw steels toughened with nickel, both forgive forge heat treating, and both sit in the elite toughness class. 15N20 carries twice the nickel and a damascus day job; 8670 carries a lower price and thicker availability. Picking between them is less about performance than about what the blade is for.
Quick Verdict
Choose 15N20 if damascus is anywhere in your future — its high nickel is the bright layer, and as a standalone steel it is excellent anyway. Choose 8670 for standalone hard-use blades where its easier-to-find knife-sized stock and lower price do the same tough job without the damascus premium.
Toughness
A family tie at the top of the charts — both ride nickel to the elite class alongside 5160, and testing puts them within noise of each other at working hardness. Nobody has ever broken a knife because they picked the wrong one of these two.
Edge Retention
Effectively even: both are fine-grained, low-wear steels with no vanadium carbides, keen off the stone and quick to dull by alloy-steel standards. 15N20's slightly higher carbon-in-solution at times gives it a hair more bite; call it a tie in use.
Corrosion Resistance
15N20 by a shade — its ~2% nickel slows rust just enough to notice, which is also why it stays bright in an etched damascus billet while 1084 goes dark. 8670 behaves like plain carbon steel. Both need oil.
Heat Treat
Nearly identical, by shared ancestry: austenitize around 1475–1500°F, fast or medium oil, temper 300–450°F, generous margins, forge-friendly. Knife Steel Nerds literally covers them in the same article. 8670's tested recipe is the more documented; 15N20's thin stock air-cools fast enough to demand slightly more quench attention.
Grinding
Both grind beautifully. The practical difference is stock: 15N20 overwhelmingly ships as thin damascus-ready sheet (often 0.065–0.095 inch), which limits standalone designs; 8670 shows up in more knife-usable thicknesses. For a mono-steel blade that alone often decides it.
Best-Use Scenarios
15N20: the bright damascus layer first and forever, plus excellent thin standalone blades — kitchen knives, fillet knives, working slicers. 8670: standalone camp knives, choppers and first knives in proper knife thicknesses, at the friendliest price in the tough-steel class.