When it comes to high-performance knife steels, two names that frequently stand out are CPM S90V and CPM CruWear. Both steels are products of Crucible Industries’ advanced powder metallurgy (PM) process, which ensures a fine-grained microstructure and uniform carbide distribution. However, they serve different purposes due to their distinct compositions and properties.
CPM S90V is known for its exceptional edge retention and wear resistance, making it a popular choice for high-end knives where cutting performance over long periods is critical. On the other hand, CPM CruWear strikes a balance between toughness and wear resistance, offering superior toughness compared to most high-alloy tool steels while still maintaining good edge retention.
In this article, we will delve into the scientific data behind these two steels by comparing their chemical compositions, performance metrics (edge retention, toughness, hardness, and corrosion resistance), heat treatment requirements, manufacturing processes, and real-world performance characteristics. We will also provide practical recommendations for knife enthusiasts based on specific use cases.
Composition Analysis
The chemical composition of a steel determines its fundamental properties such as hardness, toughness, wear resistance, and corrosion resistance. Below is a breakdown of the chemical makeup of CPM S90V and CPM CruWear:
| Element | CPM S90V (%) | CPM CruWear (%) |
|---|---|---|
| Carbon (C) | 2.30 | 1.10 |
| Chromium (Cr) | 14.00 | 7.50 |
| Vanadium (V) | 9.00 | 2.40 |
| Molybdenum (Mo) | 1.00 | 1.60 |
| Tungsten (W) | – | 1.15 |
Impact of Key Alloying Elements:
- Carbon (C): Higher carbon content in S90V contributes to its ability to form hard carbides like vanadium carbides, which significantly improve wear resistance and edge retention.
- Chromium (Cr): Chromium enhances corrosion resistance. S90V has substantially more chromium than CruWear, making it more resistant to rust.
- Vanadium (V): Vanadium forms very hard carbides that improve wear resistance and edge retention. S90V has a much higher vanadium content than CruWear, contributing to its superior edge retention.
- Molybdenum (Mo) & Tungsten (W): Both elements contribute to secondary hardening during heat treatment. CruWear’s molybdenum and tungsten content help balance its toughness with wear resistance.
Performance Metrics
Edge Retention
Edge retention is often measured using the CATRA test, which simulates cutting performance over time by measuring how much material a blade can cut before dulling.
- CPM S90V: With a CATRA score of approximately 750 mm in the standard test[6], S90V is one of the best-performing steels in terms of edge retention due to its high vanadium carbide content.
- CPM CruWear: CruWear scores around 400 mm on the CATRA test[2], which is respectable but significantly lower than S90V. However, it compensates with better toughness.
Toughness
Toughness refers to a steel’s ability to resist chipping or cracking under stress. It’s often measured using Charpy impact tests.
- CPM S90V: The impact toughness of S90V is around 19 ft-lbs at HRC 58[7]. This is considered moderate for a high-carbide steel but lower than many other knife steels due to the large volume of vanadium carbides.
- CPM CruWear: CruWear excels in toughness with values around 40 ft-lbs at HRC 60[2]. This makes it significantly tougher than S90V and suitable for applications where impact resistance is critical.
Hardness Range
Hardness is measured on the Rockwell C scale (HRC) and indicates how well a steel resists deformation under stress.
- CPM S90V: Typically hardened between HRC 58–62[8], depending on the heat treatment process.
- CPM CruWear: Can reach hardness levels between HRC 60–65[2], offering flexibility depending on the desired balance between hardness and toughness.
Corrosion Resistance
Corrosion resistance is essential for knives used in humid or corrosive environments.
- CPM S90V: With 14% chromium content, S90V offers good corrosion resistance comparable to stainless steels like CPM154 or Elmax[4]. It performs well in environments where moisture exposure is frequent but may not be as resistant as steels like M390 or LC200N.
- CPM CruWear: With only 7.5% chromium, CruWear is not classified as stainless steel. It requires more maintenance in humid environments to avoid rusting[2].
Heat Treatment Considerations
Heat treatment plays a crucial role in optimizing the properties of both steels.
CPM S90V:
- Austenitizing Temperature: Typically between 2100°F–2150°F (1150°C–1175°C)[8].
- Tempering Temperature: Double tempering at temperatures between 400°F–750°F (200°C–400°C) is recommended for optimal hardness and wear resistance[4]. A freezing treatment between tempers can enhance dimensional stability.
S90V requires precise control during heat treatment due to its high vanadium content. Improper heat treatment can lead to reduced toughness or suboptimal corrosion resistance.
CPM CruWear:
- Austenitizing Temperature: Around 1950°F (1065°C)[2].
- Tempering Temperature: Typically tempered three times at temperatures ranging from 900°F–1050°F (480°C–565°C)[2].
CruWear’s heat treatment allows for more flexibility in achieving desired properties such as increased toughness at lower temperatures or higher hardness at elevated temperatures.
Real-World Performance
Edge Stability
Edge stability refers to how well a blade maintains its sharpness without chipping or rolling under stress.
- S90V: While it offers excellent wear resistance, its edge stability can be compromised under lateral forces due to its lower toughness[9].
- CruWear: With superior toughness, CruWear offers better edge stability under impact or lateral stress[3].
Sharpening Behavior
Sharpening ease depends largely on carbide size and hardness.
- S90V: Due to the high volume of vanadium carbides, sharpening S90V can be challenging without diamond or CBN abrasives[5].
- CruWear: Easier to sharpen than S90V due to its lower carbide volume and finer grain structure[2].
Practical Applications
- S90V: Best suited for applications requiring long-term cutting performance without frequent sharpening—such as hunting knives or high-end EDC blades.
- CruWear: Ideal for heavy-duty tasks where toughness is critical—such as tactical knives or outdoor survival tools.
Manufacturing Considerations
Both CPM S90V and CPM CruWear are produced using Crucible’s powder metallurgy process, which ensures fine carbide distribution and consistent properties throughout the steel.
Cost Implications
Due to its higher alloy content and more complex production requirements, CPM S90V tends to be more expensive than CPM CruWear[1][4]. The additional cost comes from both raw material expenses and machining challenges due to the harder vanadium carbides present in S90V.
Direct Comparison Table
| Property | CPM S90V | CPM CruWear |
|---|---|---|
| Edge Retention | ~750 mm CATRA | ~400 mm CATRA |
| Toughness | ~19 ft-lbs | ~40 ft-lbs |
| Corrosion Resistance | High | Moderate |
| Maximum Hardness | HRC 62 | HRC 65 |
| Cost Factor | Higher | Lower |
Conclusion
Both CPM S90V and CPM CruWear are excellent steels but cater to different needs:
- If you prioritize edge retention above all else and don’t mind difficult sharpening processes or slightly lower toughness, then CPM S90V is your best choice.
- If you need a tougher blade that can withstand impact without chipping while still offering good wear resistance, then CPM CruWear will serve you better.
For general EDC tasks where long-term cutting performance matters more than extreme durability under stress, go with S90V. For outdoor survival tools or tactical knives where impact resistance is critical, choose CruWear.
FAQ
- What makes CPM S90V harder to sharpen than other steels?
- The high volume of hard vanadium carbides makes sharpening difficult without diamond abrasives.
- Is CPM CruWear stainless?
- No, it contains only about 7.5% chromium—less than the required amount for stainless classification.
- Can I use CPM S90V for outdoor knives?
- Yes, but be cautious about lateral forces; it excels in edge retention but isn’t as tough as other steels like CruWear.
- How does heat treatment affect these steels?
- Proper heat treatment maximizes hardness and wear resistance in both steels but requires precise control due to their alloy compositions.
Citations:
[1] https://knifesteelnerds.com/2020/09/28/s90v-and-s125v-knife-steel-history-properties-and-how-to-heat-treat/
[2] https://www.crucible.com/PDFs/DataSheets2010/dsCPM%20CruWear2015.pdf
[3] https://knifesteelnerds.com/2021/10/19/knife-steels-rated-by-a-metallurgist-toughness-edge-retention-and-corrosion-resistance/
[4] https://www.alphaknifesupply.com/Pictures/Info/Steel/CPMS90-DS.pdf
[5] https://www.youtube.com/watch?v=EvjnsKVBXKU
[6] https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
[7] https://www.crucible.com/PDFs/DataSheets2010/dsS90v1%202010.pdf
[8] https://www.linkedin.com/pulse/cpm-s90v-steel-heat-treatment-hrc-60-62-cy-tan
[9] https://forum.spyderco.com/viewtopic.php?t=84710
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