In the world of high-performance knife steels, M390 and CPM MagnaCut represent two of the most advanced options available. Both steels are engineered using powder metallurgy (PM) techniques, which result in finer grain structures and more uniform carbide distribution compared to traditional ingot steels.
This article provides a comprehensive comparison between these two steels based on scientific data, including their chemical composition, performance metrics such as edge retention, toughness, hardness, and corrosion resistance, as well as their manufacturing processes and real-world applications.
M390, developed by Böhler-Uddeholm, is renowned for its exceptional wear resistance and corrosion resistance, making it a top choice for high-end knives. On the other hand, CPM MagnaCut, created by Dr. Larrin Thomas and produced by Crucible Industries, is a newer steel designed to offer an unprecedented balance of toughness, wear resistance, and corrosion resistance.
While both steels excel in different areas, understanding their specific properties can help knife enthusiasts make an informed decision about which steel suits their needs best.
Composition Analysis
The chemical composition of a steel greatly influences its properties such as hardness, toughness, corrosion resistance, and edge retention. Below is a comparison of the chemical makeup of M390 and MagnaCut:
| Element | M390 (%) | CPM MagnaCut (%) |
|---|---|---|
| Carbon (C) | 1.90 | 1.15 |
| Chromium (Cr) | 20.00 | 10.70 |
| Vanadium (V) | 4.00 | 2.00 |
| Molybdenum (Mo) | 1.00 | 2.00 |
| Tungsten (W) | 0.60 | – |
| Niobium (Nb) | – | 0.30 |
| Nitrogen (N) | – | Trace |
Key Alloying Elements:
- Carbon (C): Carbon contributes to hardness and wear resistance by forming carbides with other elements like vanadium and chromium.
- Chromium (Cr): Chromium is essential for corrosion resistance. M390 has a significantly higher chromium content than MagnaCut, contributing to its superior corrosion resistance.
- Vanadium (V): Vanadium forms very hard vanadium carbides that improve wear resistance and edge retention.
- Molybdenum (Mo): Molybdenum enhances toughness and corrosion resistance in both steels.
- Niobium (Nb): Present in MagnaCut, niobium helps refine the grain structure and improves toughness without sacrificing wear resistance.
Performance Metrics
Edge Retention
Edge retention is often measured using the CATRA test, which simulates repeated cutting through abrasive materials.
- M390: Known for its exceptional edge retention due to its high volume of chromium-rich carbides, M390 performs slightly better than MagnaCut in this category. CATRA tests typically show M390 scoring around 750-800 mm of cut depth.
- MagnaCut: While not as wear-resistant as M390 due to its lower carbide volume, MagnaCut still offers excellent edge retention with CATRA results in the range of 700-750 mm, placing it close to premium steels like S35VN but with better toughness[6].
Toughness
Toughness is measured using the Charpy impact test, which assesses a material’s ability to absorb energy before fracturing.
- M390: With a relatively high hardness level, M390 sacrifices some toughness compared to other steels. Charpy impact tests show values around 5 ft-lbs at 61 HRC, making it more prone to chipping under heavy use[4].
- MagnaCut: One of MagnaCut’s standout features is its impressive toughness for a stainless steel. It achieves Charpy impact values of approximately 20 ft-lbs at 62 HRC, making it significantly tougher than M390[5][6]. This allows MagnaCut to be used in thinner edge geometries without the risk of chipping or breaking.
Corrosion Resistance
Corrosion resistance is crucial for knives used in wet or humid environments.
- M390: With its high chromium content (20%), M390 offers excellent corrosion resistance, making it ideal for applications where exposure to moisture is frequent[2].
- MagnaCut: Despite having lower chromium content than M390 (10.7%), MagnaCut’s optimized microstructure ensures that all chromium is in solution rather than forming carbides. This leads to superior corrosion resistance even in saltwater environments[5]. In fact, many users report that MagnaCut outperforms M390 in real-world corrosion tests[6].
Hardness Range
Both steels can achieve high hardness levels on the Rockwell C scale (HRC), which directly impacts edge retention and strength.
- M390: Typically hardened between 60-64 HRC, with optimal performance around 62 HRC for a balance between wear resistance and toughness[2].
- MagnaCut: Can be hardened up to 65 HRC with cryogenic treatment but performs best around 62-63 HRC for an ideal balance of toughness and edge retention[5].
Heat Treatment Considerations
Heat treatment plays a critical role in maximizing the performance characteristics of both M390 and MagnaCut.
Optimal Heat Treatment Parameters:
| Parameter | M390 | CPM MagnaCut |
|---|---|---|
| Austenitizing Temp. | 2150°F | 2050°F |
| Quenching | Oil/Air | Oil/Air |
| Tempering Temp. | 400°F | 400°F |
| Cryogenic Treatment | Optional | Recommended |
For both steels, achieving higher hardness levels requires precise control over heat treatment processes:
- M390: Requires careful tempering to avoid brittleness at higher hardness levels (>62 HRC). Cryogenic treatment can improve wear resistance but is not always necessary.
- MagnaCut: Benefits from cryogenic treatment due to its fine carbide structure; it helps achieve maximum hardness while maintaining excellent toughness[6]. The heat treatment process for MagnaCut is generally more forgiving than M390 because of its balanced microstructure.
Real-World Performance Characteristics
Edge Stability
Edge stability refers to how well a steel resists deformation or chipping under stress.
- M390: While offering excellent wear resistance, M390’s relatively low toughness can lead to chipping or rolling when subjected to impacts or hard materials[4].
- MagnaCut: Thanks to its superior toughness and fine carbide structure, MagnaCut excels in edge stability even at thin edge geometries[5]. This makes it ideal for knives that require sharp edges under heavy use without frequent maintenance.
Sharpening Behavior
Sharpening ease depends on both the hardness and carbide size within the steel.
- M390: Due to its high carbide volume (especially chromium carbides), M390 can be difficult to sharpen without diamond abrasives[2]. However, once sharpened, it holds an edge exceptionally well.
- MagnaCut: Easier to sharpen than M390 because of its finer carbide structure[6]. Users report that even after heavy use, MagnaCut can be brought back to a razor-sharp edge with minimal effort using standard sharpening stones.
Wear Patterns
Wear patterns refer to how evenly a blade wears down over time with use:
- M390: Exhibits slower wear due to its high wear resistance but may develop micro-chips along the edge if used on harder materials.
- MagnaCut: Wears more evenly thanks to its balanced combination of wear resistance and toughness[5]. This makes it suitable for applications involving repeated cutting tasks over extended periods without noticeable degradation.
Manufacturing Considerations
When comparing M390 and CPM MagnaCut, it’s essential to consider the manufacturing processes involved in producing these steels. Both are made using powder metallurgy (PM), a process that allows for a more uniform distribution of carbides, resulting in better overall performance compared to traditionally forged steels. However, there are differences in the specifics of their production that can affect cost and availability.
Powder Metallurgy Process
M390 is produced by Böhler-Uddeholm using their proprietary powder metallurgy process known as Microclean. This process involves atomizing molten steel into fine powder, which is then consolidated under high pressure and heat to form a solid ingot. The result is a steel with a very fine grain structure and uniform carbide distribution, which contributes to its excellent wear resistance and corrosion resistance.
CPM MagnaCut, on the other hand, is produced by Crucible Industries using their Crucible Particle Metallurgy (CPM) process. Similar to Böhler’s Microclean process, CPM involves atomizing molten steel into powder and then consolidating it. However, one of the key advantages of CPM technology is that it allows for even finer control over the distribution of carbides, leading to improved toughness without sacrificing wear resistance.
Cost Implications
The cost of producing both M390 and MagnaCut is relatively high due to the complexity of the powder metallurgy process. However, there are some differences in cost factors:
- M390: As a well-established steel with a long history of use in high-end knives, M390 tends to be more expensive due to its high chromium and vanadium content. The demand for M390 also drives up costs, as it is widely regarded as one of the best steels for premium knives.
- MagnaCut: Being a newer steel, CPM MagnaCut is not yet as widely available as M390, but its production costs are slightly lower due to its more balanced alloy composition (lower chromium and vanadium content). As production scales up and demand increases, it’s expected that MagnaCut will become more affordable relative to M390.
Ease of Manufacturing
Both M390 and MagnaCut are challenging to machine due to their hardness and wear resistance. However, MagnaCut’s finer carbide structure makes it somewhat easier to work with during manufacturing processes like grinding and polishing.
- M390: The high volume of hard chromium carbides makes M390 more difficult to machine and grind compared to many other steels. This can increase production time and costs for knife makers.
- MagnaCut: Due to its optimized microstructure with fewer large carbides, MagnaCut is easier to machine than M390 while still retaining excellent wear resistance. This makes it more attractive for knife makers who want a balance between performance and ease of manufacturing.
Direct Comparison Table
To summarize the key differences between M390 and CPM MagnaCut, here is a direct comparison table:
| Property | M390 | CPM MagnaCut |
|---|---|---|
| Edge Retention | 750-800 mm (CATRA) | 700-750 mm (CATRA) |
| Toughness | 5 ft-lbs (Charpy) | 20 ft-lbs (Charpy) |
| Corrosion Resistance | Excellent | Superior |
| Maximum Hardness | 64 HRC | 65 HRC |
| Cost Factor | Higher | Moderately High |
| Ease of Sharpening | Difficult | Easier |
| Wear Resistance | Very High | High |
Practical Applications
Both M390 and CPM MagnaCut are highly versatile steels that excel in different applications depending on the specific needs of the user.
Best Uses for M390
- Everyday Carry (EDC) Knives: M390’s excellent edge retention makes it ideal for EDC knives that need to maintain sharpness through daily use without frequent sharpening.
- Outdoor Knives: The superior corrosion resistance of M390 makes it well-suited for outdoor knives that may be exposed to moisture or harsh environments.
- High-End Collectibles: Due to its reputation as one of the best-performing steels on the market, M390 is often used in premium collectible knives where performance and aesthetics are equally important.
Best Uses for CPM MagnaCut
- Hard-Use Knives: Thanks to its outstanding toughness, MagnaCut is ideal for hard-use knives such as survival or bushcraft blades that need to withstand impacts without chipping or breaking.
- Kitchen Knives: The combination of toughness, wear resistance, and corrosion resistance makes MagnaCut an excellent choice for kitchen knives that require fine edges but also need durability in wet environments.
- Thin-Edged Knives: Because MagnaCut maintains excellent edge stability even at thin geometries, it’s perfect for knives like fillet knives or slicers where precision cutting is required.
Real-World Performance Feedback
While laboratory tests provide valuable insights into how these steels perform under controlled conditions, real-world feedback from users also plays an important role in understanding their practical applications.
Edge Stability
In real-world use, many knife enthusiasts report that:
- M390 performs exceptionally well in tasks requiring long-term edge retention but may suffer from micro-chipping if used on hard materials like bone or metal.
- MagnaCut, with its superior toughness, handles impacts better than M390 without chipping or rolling at thin edges. Users find that MagnaCut blades can be used aggressively without fear of damaging the edge.
Sharpening Behavior
Sharpening behavior has been another point of comparison:
- Users often note that sharpening M390 requires diamond stones or ceramic sharpeners due to its high carbide content. Once sharpened, however, it holds an edge for an extended period.
- In contrast, MagnaCut’s finer carbide structure allows it to be sharpened more easily using conventional sharpening stones while still maintaining excellent edge retention.
Wear Patterns
Wear patterns observed during extended use also differ between the two steels:
- M390 tends to develop micro-chips along the edge after prolonged use on harder materials.
- MagnaCut wears more evenly over time due to its balanced combination of toughness and wear resistance. This results in fewer noticeable imperfections along the cutting edge after extended use.
Frequently Asked Questions (FAQs)
- Which steel holds an edge longer: M390 or MagnaCut?
- In controlled tests like CATRA, M390 holds an edge slightly longer than MagnaCut due to its higher carbide volume. However, in real-world use where toughness plays a role, MagnaCut may outperform M390 by resisting chipping under heavy use.
- Is MagnaCut easier to sharpen than M390?
- Yes, thanks to its finer carbide structure, MagnaCut is generally easier to sharpen than M390 using standard sharpening stones.
- Which steel is better for corrosion resistance?
- While both steels offer excellent corrosion resistance, many users report that MagnaCut performs slightly better in saltwater environments despite having lower chromium content than M390.
- Can I use either steel for kitchen knives?
- Yes! Both steels are suitable for kitchen knives; however, MagnaCut’s superior toughness may make it a better choice for thinner blades used in precision cutting tasks like filleting or slicing.
- Which steel should I choose for an outdoor survival knife?
- For outdoor survival knives where toughness is critical (e.g., chopping wood or batoning), CPM MagnaCut would be the better choice due to its superior impact resistance compared to M390.
Conclusion: Which Steel Should You Choose?
When deciding between M390 and CPM MagnaCut for your next knife purchase or custom build project, consider your specific needs:
- If you prioritize extreme edge retention and corrosion resistance above all else—especially in environments with frequent exposure to moisture—M390 may be your best option.
- On the other hand, if you need a blade that can handle tough tasks without chipping while still offering excellent wear resistance and corrosion protection—especially at thin edges—then CPM MagnaCut would likely serve you better.
Both steels represent top-tier options within the knife industry today; however, each excels in different areas based on their unique chemical compositions and performance characteristics.
Citations:
[1] https://cdn.prod.website-files.com/65dccaa56e9f327ead622d79/66fb42a7c32c18d3273c487a_pesagolizebo.pdf
[2] https://nobliecustomknives.com/m390-steel/
[3] https://forum.spyderco.com/viewtopic.php?t=94034
[4] https://www.reddit.com/r/knifeclub/comments/11tra45/magnacut_vs_m390/
[5] https://www.knifeart.com/magnacut.html
[6] https://knifesteelnerds.com/2021/03/25/cpm-magnacut/
[7] https://nobliecustomknives.com/elmax-steel/
[8] https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by-a-metallurgist-toughness-edge-retention-and-corrosion-resistance/
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