In the world of high-performance knife steels, S90V and S45VN are two premium options that have garnered attention for their unique properties. Both steels are produced by Crucible Industries using the Crucible Particle Metallurgy (CPM) process, which enhances their performance by creating a uniform distribution of carbides. However, despite their similar origins, these steels serve different purposes based on their chemical composition, edge retention, toughness, and corrosion resistance.
- S90V is known for its exceptional wear resistance and edge retention, making it ideal for applications where long-lasting sharpness is crucial.
- S45VN, on the other hand, strikes a balance between wear resistance, toughness, and corrosion resistance, offering a more versatile performance suitable for everyday carry (EDC) knives.
This article will delve into the scientific data behind these steels, comparing them across various measurable properties such as chemical composition, CATRA edge retention results, toughness, hardness ranges, and corrosion resistance. We will also explore their manufacturing processes, heat treatment requirements, and real-world performance characteristics to help you choose the right steel for your needs.
Composition Analysis
The chemical composition of a steel significantly influences its properties. Below is a comparison of the elemental makeup of S90V and S45VN:
| Element | S90V (%) | S45VN (%) |
|---|---|---|
| Carbon (C) | 2.30 | 1.48 |
| Chromium (Cr) | 14.00 | 15.00 |
| Vanadium (V) | 9.00 | 3.00 |
| Molybdenum (Mo) | 1.00 | 2.00 |
| Niobium (Nb) | – | 0.50 |
| Nitrogen (N) | – | Trace |
Key Alloying Elements
- Carbon: Higher carbon content in S90V (2.30%) contributes to its superior hardness and wear resistance but can also make it more brittle compared to S45VN.
- Chromium: Both steels contain high levels of chromium (14% in S90V and 15% in S45VN), which enhances corrosion resistance. However, S45VN’s slightly higher chromium content gives it an edge in resisting rust.
- Vanadium: The high vanadium content in S90V (9%) forms hard vanadium carbides that significantly improve wear resistance and edge retention compared to the lower vanadium content in S45VN (3%).
- Niobium and Nitrogen: These elements in S45VN contribute to its improved toughness and corrosion resistance without sacrificing too much wear resistance.
Performance Metrics
Edge Retention: CATRA Test Results
The CATRA test measures how many standardized silica-impregnated cards a knife can cut before dulling. This test is widely used to quantify edge retention.
- S90V: With its high vanadium carbide content, S90V excels in edge retention, achieving approximately 180-200% of the baseline set by 440C steel[4].
- S45VN: While not as extreme as S90V, S45VN still offers excellent edge retention at around 143% of 440C, making it a solid choice for users who need a balance between edge retention and ease of sharpening[4].
Toughness: Charpy Impact Test
Toughness refers to a steel’s ability to resist chipping or breaking under impact. The Charpy impact test measures this property.
- S90V: Due to its high hardness and carbide volume, S90V sacrifices toughness for wear resistance. Its Charpy C-notch impact values are lower than those of more balanced steels like S45VN.
- S45VN: With its rebalanced chemistry that includes niobium and nitrogen, S45VN offers improved toughness compared to both S35VN and S90V[4]. This makes it less prone to chipping during heavy use or side loading.
Corrosion Resistance
Both steels are stainless due to their high chromium content, but there are differences in how they perform in corrosive environments.
- S90V: Offers excellent corrosion resistance due to its chromium content but slightly lags behind because much of the chromium is tied up in carbides rather than being free in the matrix[3].
- S45VN: With more free chromium available due to its lower vanadium content, S45VN provides better corrosion resistance than S90V[4]. This makes it more suitable for environments where moisture exposure is frequent.
Hardness Range
The hardness of a steel directly impacts its edge retention and toughness balance.
- S90V: Typically hardened to around 58-61 HRC, offering excellent wear resistance but at the cost of some toughness[1].
- S45VN: Can be hardened slightly higher than S35VN at around 59-61 HRC, providing a good balance between hardness and toughness[4].
Heat Treatment Considerations
Heat treatment plays a crucial role in optimizing the properties of both steels.
Optimal Heat Treatment Parameters
- S90V:
- Austenitizing temperature: Around 2050°F (1120°C) for maximum hardness.
- Tempering temperature: Typically tempered at around 500°F (260°C) twice for optimal performance[3].
- S45VN:
- Austenitizing temperature: Around 1950°F–2000°F (1065°C–1095°C).
- Tempering temperature: Double tempering at around 600°F (315°C) is recommended for achieving maximum toughness without sacrificing too much hardness[4].
Heat Treatment Challenges
- S90V can be more challenging to heat treat due to its high carbide volume. Achieving uniform hardness across the blade requires precise control over temperatures.
- In contrast, S45VN, while still requiring careful heat treatment due to its complex alloying elements like niobium and nitrogen, is generally easier to work with than S90V[4].
Real-World Performance
Edge Stability
Edge stability refers to how well a blade maintains its sharpness under stress without deforming or chipping.
- S90V‘s high wear resistance ensures that it maintains an incredibly sharp edge over time but can be prone to micro-chipping if used improperly due to its brittleness.
- On the other hand, S45VN, with better toughness characteristics, offers greater edge stability under heavy use or lateral forces.
Sharpening Behavior
Sharpening harder steels with high carbide volumes can be challenging.
- S90V, with its abundance of vanadium carbides, is notoriously difficult to sharpen using conventional sharpening stones. Diamond or ceramic stones are recommended for maintaining an edge on this steel.
- In contrast, while still hard-wearing, S45VN is easier to sharpen than S90V due to its lower vanadium content[4].
Wear Patterns
Both steels exhibit excellent wear patterns thanks to their carbide structures.
- S90V’s wear pattern tends toward long-term durability with minimal deformation over time but may develop micro-chips with improper use.
- In comparison, S45VN’s wear pattern shows less micro-chipping due to its enhanced toughness while still offering good wear resistance.
Manufacturing Considerations
Both steels are produced using Crucible’s CPM process—a form of powder metallurgy that creates fine-grained steel with uniform carbide distribution.
Production Method
The CPM process used for both steels results in:
- Enhanced dimensional stability
- Superior grindability compared to conventionally produced steels
However:
- The higher vanadium content in S90V makes it more difficult and expensive to manufacture compared to the more balanced composition of S45VN, which contains less vanadium but adds niobium for improved performance at a lower cost[3][4].
Cost Implications
Due to its higher vanadium content and extreme wear resistance properties:
- Knives made from S90V tend to be more expensive both in terms of raw material cost and manufacturing complexity.
- In contrast, knives made from S45VN, while still premium-priced due to their performance characteristics, are generally more affordable than those made from S90V[1][4].
Heat Treatment Considerations
Heat treatment is a critical factor in unlocking the full potential of any steel, and both S90V and S45VN require precise thermal processes to achieve their optimal properties. The differences in their chemical compositions directly affect how they should be heat-treated to balance hardness, toughness, and corrosion resistance.
S90V Heat Treatment
As a high-vanadium steel, S90V requires a more complex heat treatment process to achieve its maximum hardness and wear resistance. The high vanadium content leads to the formation of hard vanadium carbides, which are excellent for wear resistance but can make the steel more brittle if not treated correctly.
- Austenitizing Temperature: For S90V, the recommended austenitizing temperature is approximately 2050°F (1120°C). This high temperature ensures that the vanadium carbides are dissolved correctly in the matrix, contributing to its extreme wear resistance.
- Tempering: After austenitizing, S90V typically undergoes two tempering cycles at around 500°F (260°C). This helps to relieve internal stresses and stabilize the martensitic structure without sacrificing too much hardness.
- Cryogenic Treatment: To further enhance wear resistance, many manufacturers also recommend cryogenic treatment (sub-zero quenching) after austenitizing. This process helps convert retained austenite into martensite, increasing hardness and dimensional stability.
S45VN Heat Treatment
S45VN, while still requiring careful heat treatment due to its advanced alloying elements like niobium and nitrogen, is generally easier to work with than S90V. The presence of niobium carbides instead of just vanadium carbides allows for a more balanced approach between toughness and wear resistance.
- Austenitizing Temperature: For S45VN, the optimal austenitizing temperature is slightly lower than that of S90V, typically around 1950°F–2000°F (1065°C–1095°C). This lower temperature helps retain more toughness while still achieving high hardness.
- Tempering: Like S90V, S45VN also benefits from double tempering. However, the tempering temperature for S45VN is usually set higher at around 600°F (315°C). This allows for an excellent balance between hardness and toughness without compromising corrosion resistance.
- Cryogenic Treatment: While not as essential as for S90V, cryogenic treatment can still be applied to S45VN to maximize hardness and dimensional stability.
Heat Treatment Challenges
- S90V: Due to its high carbide volume, achieving uniform hardness across the blade can be challenging. Precise control over temperatures during austenitizing and tempering is crucial to avoid brittleness.
- S45VN: While still requiring careful heat treatment, S45VN is generally easier to work with than S90V due to its more balanced composition. The addition of niobium makes it less prone to brittleness while still offering excellent wear resistance.
Real-World Performance
In real-world applications, the performance of knife steels like S90V and S45VN depends on several factors beyond just their chemical composition or heat treatment. These include edge geometry, sharpening behavior, wear patterns under actual use conditions, and how well they hold up in various environments.
Edge Geometry Impact
The edge geometry of a knife—whether it’s thin or thick behind the edge—can significantly impact how well a steel performs in cutting tasks.
- S90V: Due to its extreme wear resistance and relatively low toughness compared to other steels like S45VN or M390, knives made from S90V tend to perform best with thinner edge geometries designed for slicing tasks rather than heavy-duty chopping or prying.
- S45VN: With improved toughness over both S35VN and S90V, knives made from S45VN can handle more aggressive edge geometries without chipping or rolling under pressure. This makes it suitable for both slicing tasks and light-duty chopping or prying.
Sharpening Characteristics
One of the most noticeable differences between these two steels comes down to sharpening behavior.
- S90V: Due to its high vanadium carbide content (9%), sharpening S90V requires specialized equipment such as diamond stones or ceramic stones. Conventional sharpening stones will struggle against the hard vanadium carbides embedded in the steel matrix. While difficult to sharpen initially, once sharpened properly, an edge made from S90V will last significantly longer than most other steels.
- S45VN: Although still harder than many other steels due to its carbide structure (including niobium carbides), S45VN is easier to sharpen than S90V. It responds better to conventional sharpening stones and doesn’t require diamond abrasives unless you’re looking for a mirror-polished edge.
Wear Patterns
Both steels exhibit excellent wear patterns thanks to their carbide structures; however, there are some differences based on their intended use cases:
- S90V Wear Pattern: With its high vanadium carbide content, S90V tends toward long-term durability with minimal deformation over time. However, it may develop micro-chips if used improperly or in situations that require lateral forces on the blade.
- S45VN Wear Pattern: In contrast, S45VN’s wear pattern shows less micro-chipping due to its enhanced toughness while still offering good wear resistance. This makes it more forgiving in situations where lateral forces might be applied during cutting tasks.
Practical Applications and Limitations
When choosing between these two steels for knife applications, it’s essential to consider how they will perform in real-world scenarios:
- S90V Practical Applications:
- Best suited for applications where extreme edge retention is required over long periods without frequent sharpening.
- Ideal for hunting knives, skinning knives, or other tools that need to maintain sharpness through extended use.
- Not recommended for heavy-duty chopping or prying tasks due to its lower toughness compared to other steels like CPM 3V or even S45VN.
- S45VN Practical Applications:
- Offers excellent versatility with a balance between edge retention, toughness, and corrosion resistance.
- Suitable for everyday carry (EDC) knives where users need both durability and ease of maintenance.
- Can handle light-duty chopping or prying tasks better than S90V without chipping or rolling at the edge.
Manufacturing Considerations
Both steels are produced using Crucible’s CPM process—a form of powder metallurgy that creates fine-grained steel with uniform carbide distribution. However, there are some differences in manufacturing complexity and cost implications between these two steels.
Production Method
The CPM process used for both steels results in:
- Enhanced dimensional stability
- Superior grindability compared to conventionally produced steels
- Improved toughness due to finer grain structures
However:
- The higher vanadium content in S90V makes it more difficult and expensive to manufacture compared to the more balanced composition of S45VN, which contains less vanadium but adds niobium for improved performance at a lower cost.
Cost Implications
Due to its higher vanadium content and extreme wear resistance properties:
- Knives made from S90V tend to be more expensive both in terms of raw material cost and manufacturing complexity.
In contrast:
- Knives made from S45VN, while still premium-priced due to their performance characteristics, are generally more affordable than those made from S90V.
Direct Comparison Table
| Property | CPM-S90V | CPM-S45VN |
|---|---|---|
| Edge Retention | 180%-200% of 440C | 143% of 440C |
| Toughness | Lower | Higher |
| Corrosion Resistance | High | Higher |
| Maximum Hardness | 58–61 HRC | 59–61 HRC |
| Cost Factor | Higher | Moderate |
Conclusion
When deciding between CPM-S90V and CPM-S45VN for your next knife purchase or custom build project:
- If you prioritize extreme edge retention above all else—especially in applications where you won’t be resharpening frequently—then CPM-S90V is your best bet. It’s ideal for hunting knives or skinning blades that need long-lasting sharpness but won’t face heavy-duty impacts.
- On the other hand, if you’re looking for a more versatile steel that balances edge retention with improved toughness and corrosion resistance—especially for everyday carry (EDC) knives—then CPM-S45VN offers a better all-around performance at a slightly lower cost.
Ultimately, your choice should depend on how you plan to use your knife:
- For lightweight slicing tasks where longevity is key: choose CPM-S90V.
- For general-purpose use with occasional heavy-duty tasks: choose CPM-S45VN.
FAQs
- Which steel is harder—S90V or S45VN?
- Both can achieve similar hardness levels (58–61 HRC), but S90V tends toward slightly higher hardness due to its higher carbon content.
- Is S45VN easier to sharpen than S90V?
- Yes. Due to its lower vanadium content, S45VN sharpens more easily using conventional stones compared to the extremely hard vanadium carbides found in S90V.
- Which steel has better corrosion resistance?
- While both are stainless steels with high chromium content, S45VN offers slightly better corrosion resistance thanks to more free chromium in its matrix.
- Can I use an S90V knife for heavy-duty tasks?
- It’s not recommended due to its lower toughness; instead consider using CPM-S45VN or other tougher steels like CPM 3V for such tasks.
- Why is CPM-S90V more expensive?
- The higher vanadium content makes it harder and costlier to produce through powder metallurgy processes compared to CPM-S45VN.
Citations:
[1] https://blog.hdmdknives.com/s90v-steel.html
[2] https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by-a-metallurgist-toughness-edge-retention-and-corrosion-resistance/
[3] https://www.crucible.com/eselector/prodbyapp/plastics/s90vp.html
[4] http://www.crucible.com/PDFs/DataSheets2010/dsS45VN%20rev%202.pdf
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