S45VN and CPM 20CV are premium powder metallurgy stainless steels made by Crucible Industries using their Crucible Particle Metallurgy (CPM) process.
The CPM process results in a fine, consistent carbide structure and superior properties compared to conventional steels.
S45VN is the latest iteration after S30V and S35VN providing improved corrosion resistance and toughness.
CPM 20CV stainless steel is comparable to other top-tier knife steels like Bohler’s M390 and Carpenter’s 204P. CPM 20CV is renowned for its extreme wear resistance and corrosion resistance.
20CV provides outstanding edge retention but CPM S45VN offers better all-around performance for knife properties like toughness while still having excellent edge holding ability.
20CV vs S45VN At A Glance
| Property | CPM S45VN Steel | CPM 20CV Steel |
|---|---|---|
| Toughness | Better | Lower |
| Hardness | 59-62 HRC | 58-59 HRC |
| Edge Retention | Very good, similar to S30V | Extremely high, about 25% better than S45VN |
| Corrosion Resistance | Good, Lower than 20CV | Better than S45VN, similar to M390 |
| Ease of Sharpening | Moderate difficulty | More difficult than S45VN |
| Composition | 3% V, 16% Cr, 2% Mo | 4% V, 20% Cr, 1% Mo, 0.6% W |
| Recommended For | Most users | Demanding applications needing maximum edge retention |
Toughness
Toughness is the ability of knife steel to resist cracking, chipping, or breaking under impacts during use.
When comparing toughness, S45VN has somewhat better toughness and impact resistance versus 20CV for knife applications.
The high alloy content of 20CV, including 4% vanadium and 20% chromium, enables substantial carbide formation.
This improves wear resistance but reduces toughness. In contrast, S45VN has slightly lower alloy content at 3% vanadium and 16% chromium, resulting in a lower overall carbide volume fraction.
Experimental Charpy impact testing showed S45VN achieved 11-12 ft-lbs toughness when properly heat treated, compared to around 10 ft-lbs for S30V.
On the other hand, 20CV steel has a typical Charpy impact toughness of only 6-8 ft-lbs.
The finer and more evenly dispersed carbides in S45VN steel, along with its higher toughness matrix, give it an advantage in fracture resistance.
For knives, the better toughness of S45VN reduces the risk of chipping, cracking, or catastrophic failure when subjected to high impacts or lateral forces.
S45VN exhibits moderately better toughness and impact resistance compared to 20CV which may give it an advantage for demanding knife uses or larger blades
Hardness
S45VN steel and 20CV steel can reach similar levels of Rockwell Hardness, there is no difference between them.
Crucible recommends an aim hardness of 59-61 HRC for knives for each of these two steels. The only thing that will differentiate the hardness of these two-blade steels is the heat treatment applied.
S45VN has 3% vanadium, 16% chromium, and 2% molybdenum. In comparison, 20CV is even more highly alloyed with 4% vanadium, 20% chromium, 1% molybdenum, and 0.6% tungsten.
The higher alloy content of 20CV enables it to achieve somewhat greater hot hardness particularly due to tungsten in the peak heat treatment condition.
High Hot Hardness enables CPM 20CV steel to be used in high-temperature applications without adverse effects on the properties of the steel; this however does not have a greater effect on knives.
However, S45VN offsets this to some degree by having higher nitrogen which helps strengthen the matrix.
Edge Retention
20CV steel has significantly higher edge retention and wear resistance compared to S45VN steel.
According to crucible data sheets, 20CV has a CATRA (Cutlery and Allied Trades Research Association) edge retention rating of 180% relative to 440C steel, while S45VN is rated at 143% of 440C.
The higher 4% vanadium content of 20CV steel enables more hard vanadium carbides to form, improving abrasion resistance.
However, S45VN still has very good edge-holding capability, similar to Elmax steel per independent testing.
For knives, the superior edge retention of 20CV means the edge stays sharper for longer between resharpening.
Corrosion Resistance
When it comes to corrosion resistance, 20CV and S45VN are stainless steel with very good corrosion resistance.
However, CPM 20CV stainless steel exhibits better corrosion resistance than S45VN stainless steel for knife applications.
S45VN has 16% chromium and 2% molybdenum in its composition, In comparison, 20CV is comprised of 20% chromium and 1% molybdenum.
The higher 20% chromium content gives 20CV better overall corrosion resistance.
This is because more chromium in 20CV will be left in the solution that helps protect against corrosion.
Although S45VN has higher chromium at 16%, some of it is used in the formation of chromium carbide leaving some chromium in solution but not nearly as much as 20CV steel.
Experimental testing showed 20CV steel performed similarly to 204P/M390 steel in a salt spray test.
The better corrosion resistance of 20CV steel means the blade will be more stain and rust-resistant when exposed to moisture, acids, salt, etc.
However, for highly corrosive environments, nitrogen-alloyed steels like LC200N or H1 would be a better choice than either S45VN or 20CV.
Ease of sharpening
S45VN steel has a slight advantage in ease of sharpening compared to 20CV for knife applications.
While both are considered moderately difficult to sharpen due to their high alloy contents, S45VN slightly lower carbide content and finer carbides provide a small advantage in ease of sharpening over 20CV steel for knives.
With 4% vanadium, 20CV forms a higher carbide content than S45VN which has 3% vanadium.
The high volume fraction of extremely hard vanadium carbides in 20CV can make it more difficult to abrade and sharpen.
Additionally, S45VN steel contains some niobium carbides which are finer than vanadium carbides.
The lower overall carbide content and finer carbide size distribution in S45VN steel improve its grindability and sharpenability.
However, both steels are considered more difficult to sharpen than lower alloy steels like 440C or AUS-8 due to their high hardness and abrasion resistance.
For sharpening knives, diamond stones or ceramic stones are recommended. 20CV’s very high wear resistance means it takes longer to form a keen edge compared to S45VN.
However, even S45VN steel still requires patience and skill to sharpen properly.
Final Thoughts on 20CV vs S45VN
In summary, 20CV provides outstanding edge retention but S45VN offers better all-around performance for knife properties like toughness while still having excellent edge holding ability.
In summary, while both 20CV and S45VN are excellent knife steels, they have some key differences that may make S45VN a better choice for most users.
The main advantage of 20CV is its extremely high wear resistance and edge retention due to its very high vanadium content.
However, this also makes 20CV more difficult to sharpen once the edge eventually dulls. In my experience, I have found sharpening 20CV to be quite challenging, especially when trying to reprofile or sharpen at low angles.
S45VN offers nearly as good edge retention as 20CV but with better all-around properties like toughness, and ease of sharpening.
The slightly lower alloy content and finer carbides in S45VN provide an advantage in sharpenability over 20CV.
For most knife uses, S45VN’s balance of edge retention, toughness, and easier sharpening makes it a better choice.
While advanced knife enthusiasts may appreciate 20CV’s extreme edge retention, S45VN is likely the better option for most thanks to its easier maintenance when the time comes to resharpen the edge.