Carbon or stainless steel: which steel for a knife blade?

Choosing a knife steel always means weighing three qualities that never move forward together: hardness, which holds the edge, toughness, which keeps the blade from chipping, and corrosion resistance. The metallurgical analyses published on Knife Steel Nerds confirm it, improving one of these qualities almost always costs on another: a steel that is best in absolute terms does not exist, only a steel better suited to a given use.

A carbon steel is, by definition, an alloy of iron and carbon (0.05 to 2.1% by mass) with few other elements: this simplicity gives it a fine edge that is easy to maintain, at the cost of real sensitivity to rust. A steel becomes stainless past a precise threshold, at least 10.5% chromium, which forms a thin protective layer on its surface. In between, a semi-stainless steel carries chromium without meeting the full threshold: this is the case of the D2 worked at the workshop. The five grades Le Résiliant works there, 90MCV8 carbon, D2 (or Z160), N690, 14C28N and damascus, sit across this triangle.

On a Résiliant 2.0, the patina is not a flaw but the trace of a living steel: through contact with cutting and air, the 90MCV8 develops a blue grey veil that evolves over years and with its owner's use. Unlike rust, which eats away at the metal, the patina is a thin oxide layer that instead protects the surface it covers.

The 90MCV8's grind is also finer than the Tanto's, which adds to its sought after edge; the same grade equips the carbon version of the Shotokan. The trade-off is simple: a sharper, easier to revive edge, in exchange for slightly closer care, wiping the blade after use, keeping it dry, adding a drop of oil now and then.

This steel goes by two names depending on the continent: O2 in the United States, 90MCV8 in France, and it is the same metal. Cutlery lives with these double designations, much as the American D2 is called Z160 by the French standard.

It is also the steel of hunting daggers, chosen for its resilience: it takes an impact without breaking, and it comes back to true very easily on a butcher's steel.

The old prejudice holds that a stainless can never cut as well as a carbon steel: it comes from older stainless grades, loaded with chromium to resist corrosion at the cost of cutting performance. Modern grades like N690 or 14C28N are designed differently, with a better balance of hardness and resistance, and refined specifically for cutlery rather than borrowed from other industrial uses.

The Mini Tanto, fitted with this N690 and a carbon fibre handle, is meant as the most carefree of the Résiliants: its grade resists wear and oxidation well, an advantage for humid use or for anyone who sometimes forgets to wipe the blade. The Tracker, in 14C28N, targets the same profile with a blade coating available on request, at the quote stage, a stainless grade built for a mid-range budget without giving up on cutting performance.

The workshop itself speaks of D2 Z160: the same tool steel, just two designations under different standards, American and European. Rich in carbon and chromium, it holds a demanding edge and resists abrasion well, which is why it equips the Résiliants built for job site or everyday use, starting with the Tanto, the original model in the collection.

Le Mancharicou takes it up in a more compact format, and Le Shotokan comes in a Z160 semi-stainless version alongside its carbon one. Semi-stainless does not mean stainless: D2 tolerates moisture better than a carbon steel, but a D2 blade left wet in its sheath still stays exposed to corrosion, and always benefits from being wiped before storage.

These orders of magnitude sit within what the CTIF documents: austenitisation of a steel begins at around 723°C, and hardening itself falls, depending on the grade, between 780 and 1250°C. The workshop's temperature controlled electric furnace makes it possible to hold these ranges precisely, and to tailor the treatment to each steel rather than applying one recipe to all.

The workshop does not work steels whose hardening calls for 1100 to 1200°C, those high tech American grades. The collection sticks to the five grades the furnace in Thiers can handle, from carbon to stainless, with the cryogenic step for the N690 and the 14C28N left to industry. It is a limit stated rather than hidden, and it says what matters: a steel gives nothing without the heat treatment that matches it.

The full story of the shaping, from cutting to grinding, is told in the Journal article on how a Résiliant is made, from steel plate to finished knife: what matters here is that hardening shapes the edge, and how long it lasts, just as much as the initial choice of grade.

Damascus deserves a word of its own: it comes in both carbon and stainless. Carbon damascus, forged by a bladesmith through pattern welding, behaves at the care stage like any carbon steel, wiped and kept dry; it is the variant the workshop reserves for L'Archétype, for the damascus version of Le Shotokan and, on request, for Le Fhiers, and its patterns are covered in the article "Damascus steel: how the patterns of a blade are born". Stainless damascus, on the other hand, cannot be forged by an artisan bladesmith, only industry can produce it: the workshop buys it already shaped, for clients who ask for it at the quote stage.

Beyond the grade, the choice of a steel is always made directly with the cutler, at the quote stage: he is the one who knows how each grade actually behaves across the eight models in the collection, and who helps match a steel to a use rather than a trend. That choice, like the model or the handle material, sits at the heart of a craft practised in Thiers, where every blade is tempered, assembled and adjusted by hand.