S90V and 20CV are two premium stainless steels made by Crucible Industries using their advanced Crucible Particle Metallurgy (CPM) production process.
This specialized powder metallurgy process enables very fine and uniform carbide distributions in these highly alloyed steels.
CPM 20CV stainless steel is considered comparable to other top-tier knife steels like Bohler’s M390 and Carpenter’s 204P.
CPM S90V and 20CV aim to provide a balance of high wear resistance, corrosion resistance, and reasonable toughness for use in high-end blades and knives.
The key difference between S90V and 20CV steel lies in their edge retention and wear resistance capabilities.
For those focused on unmatched edge retention and wear resistance in stainless knife steel, S90V is the better choice over 20CV.
But for better corrosion resistance and ease of sharpening, 20CV can be an appealing alternative to extremely wear-resistant steels like S90V.
S90V vs 20CV At A Glance
| Property | S90V Steel | 20CV Steel |
|---|---|---|
| Hardness | 66 HRC (optimal), 56-59 HRC (recommended) | 59-61 HRC |
| Edge Retention | Extremely high, CATRA score over 250 at 58 HRC | High, CATRA score around 180 at 58 HRC |
| Corrosion Resistance | Moderate, 14% Cr | Excellent, 20% Cr |
| Toughness | Low, around 19 ft-lbs at 58 HRC | Low, similar to S90V |
| Sharpenability | Very difficult due to high vanadium carbide volume | Easier than S90V but still challenging |
| Composition | 2.3% C, 14% Cr, 1% Mo, 9% V | 1.9% C, 20% Cr, 1% Mo, 4% W, 0.6% |
Corrosion Resistance
20CV steel offers significantly better corrosion resistance compared to S90V steel due to its much higher chromium content.
20CV stainless steel contains 20% chromium, while S90V stainless steel only has 14% chromium.
The higher chromium content in 20CV leads to a greater formation of a protective chromium oxide passive layer to resist corrosion.
The superior corrosion resistance means 20CV can better withstand extended exposure to moisture, acids, and salts without corroding.
This makes CPM 20CV stainless steel preferable for knives used in hot, humid, or marine environments where corrosion is a major concern.
However, for most general EDC tasks, the level of corrosion resistance provided by CPM S90V is likely adequate. But for specialized applications where preventing rust is critical, 20CV will clearly outperform S90V.
Hardness
S90V steel contains a significantly higher amount of vanadium at 9% compared to 4% in 20CV steel.
This leads to S90V achieving notably higher hardness values, with optimal heat treatment resulting in around 66 HRC hardness for S90V compared to 59-61 HRC for 20CV.
However, for practical knife application, crucible data sheets recommend an aim hardness of around HRC 56/59 for both steels.
The higher hardness of S90V also leads to superior edge retention and wear resistance compared to 20CV, as seen in cutting tests like the CATRA test.
For example, in knives heat treated to 58 HRC, S90V achieved a CATRA score over 250 while CPM 20CV steel score was around 180.
While 20CV offers adequate wear resistance for many applications, S90V is better suited for uses requiring extreme edge retention.
Edge Retention
S90V offers substantially better edge retention and wear resistance compared to 20CV due to its higher hardness and vanadium carbide content.
In a CATRA cutting test performed at 58 HRC, S90V achieved a score of over 250 cuts while 20CV scored around 180 cuts.
The CATRA test directly measures edge wear resistance, so the higher result for S90V demonstrates its superior ability to retain a sharp edge.
The extreme edge holding of S90V also makes it suitable for knives used in highly demanding cutting tasks.
However, the high wear resistance comes at the cost of being more difficult to sharpen once dull. Corrosion Resistance
Ease of Sharpening
The high volume of vanadium carbides in S90V and 20CV leads to increased difficulty in sharpening and grinding compared to lower alloy steels.
However, S90V generally has poorer grindability and sharpenability relative to 20CV.
S90V contains a significantly higher amount of hard vanadium carbides at 9% vanadium versus 4% in 20CV.
The hardness and abrasion resistance of these carbides make S90V more challenging to abrade or cut during sharpening and grinding.
Sharpening S90V typically requires more effort and time on the diamond or CBN stones. For grinding knives, S90V is also slower to cut and can cause more rapid abrasive wear.
The difficulty working S90V comes with the benefit of its extreme edge retention though. While 20CV is easier to sharpen and grind than S90V, it still requires more work than lower alloys.
For applications favoring ease of maintenance over edge holding, 20CV provides a better balance. But for extended edge life with less concern over sharpening difficulty, S90V remains a good option despite its poor grindability.
Toughness
The high vanadium carbide content in S90V and 20CV leads to reduced toughness compared to other alloy steels.
There is no comparable difference between 20CV and S90V steel when it comes to toughness, the differences only arise depending on the hardness achieved. Slightly lower hardness will yield better toughness.
In Charpy C-notch impact testing performed by Crucible, S90V exhibited 19 ft-lbs toughness when heat treated to 58 HRC. In comparison, 440C steel scored 16 ft-lbs at a similar 58 HRC hardness.
Still, both S90V and 20CV have relatively low toughness that can make them more prone to chipping when used for hard tasks like chopping in knives.
For knives used in very tough tasks, lower alloy steels like 12C27 with inherently better toughness are typically preferred over either S90V or 20CV.
Final thoughts on S90V vs 20CV Steel
The key takeaway is that S90V offers substantially better edge retention and wear resistance due to its higher hardness and vanadium carbide content.
However, 20CV is more corrosion resistant and easier to sharpen thanks to its higher chromium content and slightly lower alloy content.
In my personal experience with these steels, I tend to prefer 20CV steel over S90V steel for most of my knives.
Despite having lower edge retention on paper, I’ve found 20CV steel real-world cutting ability sufficient for my needs, while also being much easier to sharpen.
The higher hardness does make S90V more difficult to sharpen and machine.
Overall, the much greater hardness and wear resistance of S90V comes at the expense of some grindability compared to 20CV, making it better suited for knives focused on extended edge retention rather than ease of maintenance.
The enhanced corrosion resistance does come at the expense of some wear resistance for 20CV relative to S90V.
So for maximizing edge retention, S90V remains the better choice if corrosion is not the primary factor.
For most purposes, I think 20CV strikes the ideal balance, but knives subjected to highly abrasive or demanding conditions may warrant opting for S90V steel extreme wear resistance despite the tradeoffs.