K390 steel was developed in the early 2000s by Bohler as an improvement over other high-vanadium steels like CPM 10V. It has seen a surge in popularity in knives after being utilized by Spyderco in the mule, police, and endura knives.
S30V was also developed in the early 2000s by Crucible Industries. It was designed in collaboration with knife makers to offer an optimal balance of edge retention, toughness, and corrosion resistance.
Both steels are produced using powder metallurgy, which results in fine, homogeneous carbide structures.
However, K390 is considered a non-stainless tool steel while S30V is a stainless steel with very good corrosion resistance.
K390 steel offers better wear resistance and edge-holding ability, though with reduced corrosion resistance.
K390 vs S30V Steel At A Glance
| Property | K390 Steel | S30V Steel |
|---|---|---|
| Hardness | Up to 66 HRC | Up to 63 HRC |
| Toughness | Better than S30V, comparable to CPM 10V | Slightly lower toughness than K390 |
| Edge Retention | Substantially better | Good edge retention but lower than K390 |
| Corrosion Resistance | Not stainless, very low corrosion resistance | Excellent corrosion resistance as a stainless steel |
| Ease of Sharpening | More difficult due to the higher volume of hard vanadium carbides | Easier to sharpen due to lower carbide content |
Hardness
K390 steel has the potential to reach higher hardness levels than S30V steel, according to the data sheets, K390 can reach a hardness of up to 66 HRC while S30V can reach a hardness of 63 HRC.
However, in practical knife applications, K390 and S30V are often heat-treated to more modest hardness levels in the 58-62 HRC range to balance wear resistance with toughness.
K390 achieves higher hardness than S30V steel due to higher amounts of hardening elements like Carbon, vanadium, molybdenum, tungsten, and cobalt.
Additionally, the high 9% vanadium in K390 steel promotes the formation of very hard vanadium carbides.
Toughness
The toughness of K390 steel is slightly better than that of S30V steel and is comparable to CPM 10V steel when properly heat treated.
K390 demonstrates marginally better toughness compared to S30V when heat treated to achieve hardness typically used in knife blades.
The toughness advantage of K390 becomes more pronounced at higher hardness levels above 62 HRC, where K390 retains its toughness better than S30V meaning it will offer better edge retention and toughness too.
Additionally, the toughness of K390 is very similar to other high-wear resistance steels like CPM 10V and Vanadis 8.
K390 knives will thus offer better toughness than S30V knives, K390 knives are even better at higher hardness levels as they offer both toughness, edge retention, and wear resistance advantage.
Edge Retention
K390 demonstrates substantially better edge retention and wear resistance compared to S30V due to its higher volume of vanadium carbides.
According to CATRA testing data, K390 steel showed around 45% better edge retention than S30V steel. K390 consistently outperforms S30V in terms of edge retention.
The high vanadium content (9%) of K390 enables it to significantly outperform S30V (4% V) in terms of edge retention and wear resistance.
The harder vanadium carbides that makeup about 17% of K390’s microstructure provide substantially better resistance to abrasive wear during cutting.
Corrosion Resistance
CPM S30V steel is a stainless steel while K390 is a non-stainless steel thus S30V steel offers superior corrosion resistance.
S30V steel offers significantly better corrosion resistance compared to K390 steel due to its higher chromium content.
S30V contains 14% chromium, which provides stain and rust resistance suitable for many knife applications.
In comparison, K390 steel only has 4.15% chromium and is considered a non-stainless steel by industry standards.
In Dr. Larrin Thomas’s corrosion testing data, S30V steel scored a 7 out of 10 rating, while K390 steel scored only a 3 out of 10 rating.
For uses that require corrosion resistance, S30V knife steel is the clear choice over K390 knife steel.
Ease of Sharpening
K390 steel is more difficult to sharpen compared to S30V steel due to its higher volume of vanadium carbides.
The high vanadium content of K390 leads to the formation of hard, abrasion-resistant vanadium carbides that make up about 17% of its microstructure.
These carbides do not grind away as easily as the steel matrix during sharpening. In comparison, S30V has a lower carbide volume at around 14.5% and contains more of the softer carbides.
The higher carbide content and harder vanadium carbides in K390 require more abrasive force and time to remove metal during the sharpening process.
However, the superior edge retention of K390 steel means it may not need to be sharpened as frequently.
But when sharpening is required, S30V’s lower overall carbide content allows it to be sharpened quicker and with less effort compared to the very wear-resistant K390.
Final thoughts on K390 vs S30V Steel
In summary, for most knife uses, S30V steel is likely the better all-around choice offering a great balance of properties.
S30V steel also maintains corrosion resistance while still having adequate wear resistance for many common cutting tasks.
However, for applications requiring maximum wear resistance and edge holding, K390 steel is the superior performer.
The alloy of K390 steel is significantly tougher while also offering enhanced wear resistance and edge retention compared to S30V.
So for uses that demand high hardness, wear resistance, long-lasting sharp edges, and toughness, I recommend K390 it is an excellent knife steel choice despite lacking corrosion resistance.
It will outperform S30V in terms of edge retention thanks to its very hard vanadium-rich carbides.
But for general-purpose knives requiring a more balanced set of properties, I recommend S30V as it maintains great wear resistance along with far better corrosion resistance compared to K390 steel.