S90V, S110V, K390, 10V: Exotica and What It Costs

The far end of the catalogue works like this: the higher a steel sits in the list, the fewer knives exist in it. That is not a conspiracy among makers but a consequence of what makes a steel expensive — and it is worth unpacking before you pay.

S90V: less chromium, more vanadium

CPM S90V (formerly CPM 420V) is a very highly alloyed powder steel from Crucible. Its combination is rare: very high wear resistance and very high corrosion resistance at the same time.

What is interesting is not so much the steel as the idea built into it back in 1995. Before that, stainless knife steels were made with 16–20% chromium. S90V took 14% — and that was an improvement, not a saving. The logic runs like this: corrosion resistance comes from chromium in solution, not from chromium tied up in carbides. In a steel with 20% chromium, about 13% ends up in solution anyway; the rest went into chromium carbides, which are softer than vanadium carbides and spoil the balance of properties. By lowering the chromium and balancing the composition, the developers handed the carbide budget to vanadium. The same base level of 14% chromium was later used in S30V, S35VN and S125V.

The price of high vanadium is machinability. S90V is hard to work with, and the upper hardness limit is around 61 HRC. Kitchen knives in it barely exist: this is a material for individual makers.

S110V: niobium and awkward stock sizes

CPM S110V is the same school, one step further. Also a Crucible powder steel, also a combination of very high wear resistance with very high corrosion resistance. Its unique feature is 3.5% niobium. Niobium carbides are harder still than vanadium carbides, and the total carbide content in this steel is very high. The manufacturer’s recommended hardness is 61–63 HRC.

It has 15.25% chromium, and in corrosion resistance it is no worse than M390 with its 20% — because what matters is the whole composition, not one line in it.

And then the prose begins. Crucible supplies S110V in very inconvenient sizes, which is why knifemakers hardly ever buy it. An excellent steel whose availability is decided not by metallurgy but by the logistics of stock sizes.

K390 and CPM 10V: exotica that rusts

These two puzzle people in a kitchen setting: they are not stainless at all. But steels like these are exactly the ones that give the best balance of properties.

The logic is simple. More carbide means better wear resistance and worse toughness; this is a fundamental dichotomy and there is no way around it. But the hardness of the carbide has almost no effect on toughness. So if you use the hardest carbides — vanadium ones — and keep them fine, you can get more wear resistance at the same level of toughness. Hence the short list of steels with the best combination: powder non-stainless steels alloyed mainly with vanadium — CPM 1V, CPM 3V, Vanadis 4 Extra, CPM 4V, CPM 10V, K390, Vanadis 8.

CPM 10V is the extreme point of this approach: a great deal of hard vanadium carbide and, accordingly, very high wear resistance. It is as hard to machine as any stainless. It also illustrates how meaningless the word “carbon” is in everyday usage: 1095 and 10V are both non-stainless, but a smith works 1095 with bare hands and quenches it in water, while 10V hardens in air and resists everything.

What exactly you are paying for

The price of an exotic steel is not made of one item:

• vanadium is expensive in itself;
• powder metallurgy is a separate and costly process;
• highly alloyed steel is hard to cut, grind and drill, and that is the maker’s time;
• heat treatment is demanding, and a mistake in it wipes out the whole difference;
• runs are small, and often the reason is not even demand but the available stock sizes.

Note that none of these items is about how the knife cuts.

What you get and what you do not

You get something real: the edge dulls more slowly, sometimes by a wide margin. You do not get toughness. Once total carbide content passes 15%, high toughness is no longer on offer — and in a kitchen that shows up as chipping against bone, against the board, against a piece of shell that got in the way. Plus sharpening: what resists abrasion by food resists the abrasive just as well.

And one last thing that the descriptions of these steels leave out.

A real professional cook in a real kitchen is unlikely to be working with a knife in an exotic alloy. Such knives are a luxury item for the household, and their main purpose is to be a pleasure to use, not to earn a cook a living.

This is not a reproach to the buyer. Pleasure is a legitimate reason to spend money, and a knife in S110V really is a nice thing. It is just worth calling the purchase by its name: you are buying an object, not performance. Meanwhile the professional touches up a cheap blade on a steel and gets more done.