CPM S90V and CPM MagnaCut are two high-end stainless tool steels made using the Crucible Particle Metallurgy process.
Developed by metallurgist Dr. Larrin Thomas, MagnaCut has a composition optimized specifically for knives to improve toughness and corrosion resistance compared to previous stainless blade steels like S90V.
The key difference between these powder metallurgy stainless steels is the vanadium content.
S90V has a very high 9% vanadium while MagnaCut contains a more modest 4% vanadium along with 2% niobium.
In properties, the key difference between MagnaCut and S90V is in edge retention, S90V steel exhibits almost twice the edge retention of MagnaCut steel.
S90V vs MagnaCut Steel At A Glance
| Property | CPM S90V Steel | CPM MagnaCut Steel |
|---|---|---|
| Composition | 9% Vanadium, 14% Chromium, 2.3% Carbon, 1% Molybdenum | 4% Vanadium, 10.7% Chromium, 1.15% Carbon, 2% Molybdenum, 2% Niobium |
| Corrosion Resistance | Good like S30V | Excellent better than S90V |
| Toughness | Moderate | Higher better than S90V |
| Hardness | Aim Hardness 56-59 HRC | Aim Hardness 60-63 HRC |
| Edge Retention | Excellent | Good |
| Ease of Sharpening | Difficult | Easy |
Corrosion Resistance
MagnaCut and S90V are stainless steels with excellent corrosion resistance, however, MagnaCut has significantly better corrosion resistance compared to S90V steel.
Testing shows MagnaCut blade steel resisted corrosion as well as premium stainless steels like LC200N and Vanax, while S90V performed similarly to steels like S30V.
The higher corrosion resistance of MagnaCut is due to its lower 10.7% chromium content and lack of chromium carbides.
The lower bulk chromium content ensures all of the chromium remains in solution to provide corrosion resistance rather than being tied up in carbides.
In contrast, S90V has 14% chromium which leads to some chromium carbide formation, creating chromium-depleted regions vulnerable to corrosion.
MagnaCut also contains 2% molybdenum versus 1% molybdenum for S90V which further enhances corrosion resistance.
Optimizing MagnaCut’s composition to eliminate chromium carbides results in its superior corrosion resistance compared to S90V.
Toughness
MagnaCut knife steel has significantly higher toughness compared to S90V steel.
Testing shows MagnaCut reaches toughness values around 38 ft-lbs at 62.5 Rc hardness, while S90V only reaches around 17 ft-lbs at 61 Rc.
The higher toughness of MagnaCut is attributed to its composition and microstructure.
By eliminating chromium carbides, MagnaCut retains a fine, uniform carbide structure consisting only of vanadium and niobium carbides.
This provides greater resistance to chipping and cracking. In contrast, S90V contains higher total carbide volume, including chromium carbide, leading to larger carbide sizes and lower toughness.
MagnaCut also contains beneficial additions of nitrogen and niobium for finer carbides.
Overall, the optimized composition and resulting microstructure of MagnaCut allow it to achieve more than twice the toughness of S90V steel.
Hardness
MagnaCut steel can achieve higher hardness levels compared to S90V steel.
MagnaCut can reach up to 65 Rc hardness with cryogenic treatment, while S90V reaches a maximum hardness of 63.5 Rc based on testing data.
Crucible recommended aim hardness for S90V is very low at HRC 56/59 compared to MagnaCUt Aim hardness of HRC 60/63.
The higher hardness potential of MagnaCut is attributed to its composition – the balance of 1.15% carbon and 10.7% chromium allows for high hardness while still having good corrosion resistance by eliminating chromium carbides.
In contrast, S90V has higher chromium content at 14% which leads to more chromium carbide formation that limits its hardness.
MagnaCut also contains vanadium, niobium, and nitrogen additions that help refine the carbide structure for improved hardness.
Overall, MagnaCut can reach higher hardness than S90V due to its optimized composition that minimizes chromium carbides while maximizing hardness through small vanadium and niobium carbides.
The fine carbide structure of MagnaCut is the key factor allowing it to achieve greater hardness than S90V.
Edge Retention
CPM S90V steel has higher edge retention and wear resistance compared to CPM MagnaCut steel.
In CATRA testing, S90V scored about 195% compared to a 440C baseline while MagnaCut scored around 135% at 62.5 Rc hardness.
The higher vanadium content of S90V leads to greater wear resistance, with S90V having 9% vanadium compared to 4% in MagnaCut.
MagnaCut also contains 2% niobium which contributes some additional carbides, but the higher vanadium in S90V results in it having higher wear resistance.
Both steels achieve excellent wear resistance through high total carbide volume, though S90V has a higher volume compared to MagnaCut.
Their compositions are balanced to maximize vanadium carbides rather than chromium carbides for maximum wear resistance.
The very high volume of vanadium carbides in S90V allows it to demonstrate superior edge retention and abrasion resistance compared to MagnaCut.
In summary, S90V has higher wear resistance and edge-holding ability relative to MagnaCut due to its higher vanadium carbide content.
Ease of Sharpening
MagnaCut knife steel has better ease of sharpening and grind ability compared to S90V steel.
MagnaCut knife steel’s fine carbide structure makes it easier to grind and finish than S90V tool steel.
Crucible states that S90V steel due to its high vanadium carbide content, will be slightly more difficult than that of D2 steel and MagnaCut Steel.
The smaller vanadium and niobium carbides in MagnaCut allow it to be sharpened effectively even with aluminum oxide stones, while S90V requires diamond or CBN due to its larger vanadium carbides.
MagnaCut is also reported to be easier to deburr after grinding compared to S90V.
The finer carbide size and lower overall carbide volume of MagnaCut give it better grindability.
In terms of composition, the lower chromium and higher niobium content of MagnaCut also help refine the carbides for improved sharpening and grinding relative to S90V.
While both steels contain significant carbide volume, the more optimized carbide structure of MagnaCut makes it easier to work with compared to S90V when sharpening or grinding blades.
Final Thoughts on S90V vs MagnaCut Steel
What you need to know is that S90V offers better edge retention and wear resistance than MagnaCut Steel due to its higher vanadium carbide content.
As someone who has experienced both blade steels, I can attest to the impressive edge-holding ability of the S90V.
Albeit with the caveat that S90V can be quite challenging to sharpen, especially for those without advanced sharpening skills.
On the other hand, MagnaCut stands out for its well-balanced properties, particularly its toughness, which makes it better suited for a wider range of knives.
If you’re an experienced knife user with the patience and skills to tackle the sharpening challenge, the S90V might be an excellent choice, especially considering its remarkable edge retention.
However, for most knife users, I would highly recommend MagnaCut due to its impressive balance of properties, including corrosion resistance, toughness, and ease of sharpening.