CPM CruWear is a powder metallurgy tool steel, designed to offer superior wear resistance and toughness compared to its conventionally produced counterpart, CruWear.
This article focuses specifically on the CPM version of CruWear, which benefits from the advantages of the Crucible Particle Metallurgy (CPM) process, resulting in a more homogeneous and refined microstructure.
On the other hand, CPM S45VN is a martensitic stainless steel, also developed by Crucible using the CPM process.
S45VN builds on Crucible’s previous stainless knife steels, such as S30V and S35VN, aiming to improve upon their corrosion resistance and wear properties.
CPM CruWear boasts exceptional toughness, approximately twice that of S45VN.
This makes S45VN an excellent choice for larger knives or blades that may encounter impact or side loading.
CruWear vs S45VN Steel At A Glance
| Property | CPM CruWear Steel | S45VN Steel |
|---|---|---|
| Toughness | Exceptionally high toughness, approximately twice that of S45VN | Good toughness, but lower than CPM CruWear |
| Edge Retention/Wear Resistance | Excellent wear resistance, slightly lower than S45VN | Slightly better than CPM CruWear |
| Corrosion Resistance | Semi-stainless, lower corrosion resistance | Better corrosion resistance as a stainless steel |
| Grindability/Sharpening Ease | Easier to grind and sharpen | Slightly Harder to grind and sharpen |
| Hardness Range (HRC) | Aim hardness of 62 HRC | 59-61 HRC aim hardness |
| Stainless | Non-stainless | Stainless steel with nitrogen addition |
Corrosion Resistance
S45VN steel exhibits superior corrosion resistance compared to CPM CruWear steel, S45VN is a stainless steel while CruWear is a non-stainless steel.
S45VN steel is a more suitable choice for knives that may be exposed to corrosive environments or require enhanced stain resistance.
The improved corrosion resistance of S45VN can be attributed to its higher chromium content of 16%, compared to CPM CruWear’s chromium content of 7.5%.
Additionally, S45VN contains 2% molybdenum, which further enhances its corrosion-resistant properties.
The combination of higher chromium and molybdenum levels in S45VN results in a greater amount of these elements remaining in the solution, contributing to its superior corrosion resistance.
In contrast, CPM CruWear’s lower chromium content and absence of molybdenum make it more susceptible to corrosion and staining.
While CPM CruWear is considered semi-stainless due to its chromium content.
CruWear may not provide sufficient corrosion resistance for applications where knives are exposed to harsh environments or frequent contact with acidic substances.
S45VN would be the preferred choice for knives intended for use in outdoor activities involving saltwater exposure, or demanding kitchen environments.
Toughness
CPM CruWear steel exhibits significantly higher toughness compared to S45VN stainless steel.
The Cruwear data shows that CPM CruWear achieved a Charpy C notch impact toughness of 60 ft-lb at 60 HRC.
While S45VN Transverse Charpy C-notch impact toughness values ranged from 11-12 ft-lb, indicating that CPM CruWear possesses better the toughness of S45VN.
This superior toughness in CPM CruWear is attributed to its lower carbide volume, which is around 10% compared to the S45VN carbide volume of 15%.
The reduced carbide content in CPM CruWear results in a finer microstructure, contributing to its excellent toughness and resistance to chipping or breaking.
In knife applications, the higher toughness of CPM CruWear makes it a more suitable choice for larger knives.
CruWear knives or situations where the blade may encounter side loading or impact forces, as it can better withstand such stresses without sustaining damage.
However, S45VN lower toughness, though still respectable, may limit its application to smaller knives or scenarios where edge retention and wear resistance take precedence over impact resistance.
Hardness
CPM CruWear steel and CPM S45VN steels differ in their achievable hardness levels.
CPM CruWear can attain a Rockwell hardness of up to 65 HRC, with the recommended heat treatment aiming for 62 HRC for most knives.
On the other hand, S45VN steel can attain up to 64 HRC with an aim hardness is 59-61 HRC for knives, which is slightly lower than CPM CruWear’s target hardness.
The higher attainable hardness of CPM CruWear at higher temperatures makes it suitable for nitriding, PVD coating, or similar surface treatments that prevent rusting.
Note these surface treatments are normally carried out at very high temperatures, which may normally impact the hardness and other properties of the steel.
Edge Retention
According to the CATRA (Cutlery & Allied Trades Research Association) testing data provided, S45VN steel exhibits slightly better edge retention compared to CPM CruWear steel.
The CATRA testing, which measures the relative wear resistance by counting the number of silica-impregnated cards that can be cut shows that S45VN has a value of 143% relative to 440C stainless steel, while CPM CruWear has a lower value of around 135%.
This indicates that S45VN has an edge in terms of edge-holding capability and wear resistance.
S45VN is more suitable for knives that require exceptional slicing performance and extended periods of use without frequent sharpening.
However, the difference in edge retention between the two steels is relatively small, suggesting that CPM CruWear still offers excellent wear resistance, albeit slightly lower than S45VN.
The higher wear resistance of S45VN can be attributed to its higher carbide volume, which includes harder vanadium and niobium carbides, contributing to its superior edge retention.
Ease of Sharpening
For knife applications where ease of sharpening is a priority, CPM CruWear may be the more suitable choice due to its better grindability.
This can be particularly advantageous for knives that require frequent sharpening or for users who prefer to sharpen their knives manually.
In contrast, S45VN’s harder carbide structure may make it more difficult to sharpen, but this trade-off provides better edge retention and wear resistance.
S45VN edge retention could be beneficial for knives intended for heavy-duty or extended use before requiring sharpening.
Final Thoughts on CruWear vs S45VN Steel
From my perspective, CPM CruWear stands out for its exceptional toughness, which is approximately twice that of S45VN.
This better toughness is a result of CPM CruWear’s lower carbide volume, contributing to a finer microstructure that enhances its resistance to chipping or breaking.
I would recommend CPM CruWear for larger knives or blades that may encounter substantial impact or side-loading forces, as its superior toughness provides an added layer of durability and reliability.
S45VN’s strength lies in its corrosion resistance, thanks to its higher chromium content and the addition of molybdenum.
As stainless steel, S45VN also benefits from the nitrogen addition, which promotes the formation of hard vanadium and niobium carbides, contributing to its excellent wear resistance and edge retention.
In my opinion, S45VN would be the ideal choice for EDC knives intended for use in corrosive environments, or outdoor activities involving saltwater exposure.