M390 knife steel

M390 is the steel that made “super steel” a category. Bohler’s third-generation powder-metallurgy stainless pairs elite edge retention with genuine corrosion resistance, and for over a decade it has been the benchmark every new premium stainless gets measured against. It is also — with its near-identical siblings CPM 20CV and CTS 204P — one of the most widely used premium steels in production knives, which makes it the super stainless a custom maker’s customers have already heard of. The cost is the usual one at this end of the chart: money, belts, and patience at the sharpening bench.

M390 FAQ

Is M390 a good knife steel?

For folders, EDC blades and any knife where edge retention and rust resistance top the list, it is one of the best available. Roughly 1.9% carbon and 4% vanadium build a dense population of hard carbides that out-cut nearly everything this side of S90V, while 20% chromium keeps it comfortably stainless. The honest costs: modest toughness (thin edges on hard use can chip), real sharpening effort, and premium bar prices.

Are M390, CPM 20CV and CTS 204P the same steel?

Functionally yes. Bohler’s M390, Crucible’s CPM 20CV and Carpenter’s CTS 204P are near-identical compositions produced by different mills — the differences (a fraction of silicon, mill-to-mill powder practice) are smaller than the differences between two heat treats of the same bar. Pick by availability and price, not mystique. Full head-to-head in our M390 vs CPM 20CV comparison.

What hardness should M390 be run at?

60–62 HRC for most knives: Bohler’s tempering charts (a 2100°F austenitize, small test pieces, read by eye) show about 62 HRC at a low 210–300°F temper without a subzero step and about 63–64 with one, and Larrin Thomas’s 2140°F, plate quench, cryo, 365°F test cycle read about 62 Rc. The 390–570°F tempers Bohler recommends for the best corrosion resistance give lower hardness, roughly 57–59 HRC without subzero and about 61 with it, so a knife tempered there lands softer, which leaves edge retention on the table. Bohler’s data sheet and brochure give a 2010–2155°F austenitize with a quick quench and recommend a subzero step for the best wear resistance — kiln-and-protocol territory, not forge territory. Aluminum plates and dry ice earn their keep here; see Plate Quenching Explained.

Can you forge M390?

Practically, no — it is a stock-removal steel. The chromium carbide volume that makes it perform makes it hostile under the hammer, and its heat-treat window demands furnace precision. Buy it as bar stock, grind it, send it out or kiln it. Forgers wanting M390-class performance should read about ApexUltra — the steel designed to bring modern carbide engineering to the forge.

Is M390 hard to sharpen?

Harder than anything mainstream, easier than S90V. Vanadium carbides are harder than aluminum-oxide abrasives, so diamond or CBN stones make the job honest — conventional stones burnish more than they cut once you pass the medium grits. Owners without diamond plates will feel the difference at maintenance time; our M390 grinding guide covers belts and stones that actually work.

M390 or MagnaCut?

The modern question. MagnaCut trades a slice of M390’s edge retention for meaningfully better toughness and slightly better corrosion resistance (Larrin Thomas rates MagnaCut 9.5 and M390 9); M390 keeps the wear-resistance crown of the two. Hard-use fixed blades lean MagnaCut; pure EDC slicers and folders split on preference. See MagnaCut vs CPM 20CV — the comparison applies to M390 nearly verbatim.