Developed by Crucible Industries, CPM Cruwear is a powder metallurgy steel renowned for its superior toughness and edge stability compared to conventionally made tool steels.
The powder metallurgy production results CPM Cruwear’s exceptional wear resistance and resistance to chipping under demanding cutting conditions.
On the other hand, SPY27 is an exclusive steel formulated by Crucible for Spyderco, designed to improve upon popular stainless grades like S30V and S35VN.
As a stainless steel, SPY27 boasts better corrosion resistance than the non-stainless CPM Cruwear, making it more suitable for harsh environments.
SPY27 vs CruWear Steel At A Glance
| Properties | CPM Cruwear Steel | SPY27 Steel |
|---|---|---|
| Hardness | Up to 62-65 HRC, secondary hardening response | Up to 64 HRC with cryogenic treatment |
| Edge Retention | Comparable to SPY27 | Stainless steel, Corrosion-resistant |
| Toughness | Exceptionally higher toughness | Average Toughness |
| Corrosion Resistance | Non-stainless, above average but not stainless | Stainless steel, Corrosion Resistant |
| Ease of Sharpening | Non-stainless, above average, but not stainless | Better than CruWear steel |
| Edge Stability | Excellent, due to high toughness and uniform carbides | Good, but slightly lower than Cruwear due to lower toughness |
Hardness
CPM Cruwear can achieve hardness levels up to around 62-65 HRC, while SPY27 can reach a peak hardness of nearly 64 HRC.
CruWear higher hardness results from undergoing a secondary hardening response due to its tungsten and molybdenum content.
Higher hardness in knives generally translates to better edge retention and wear resistance but can come at the cost of reduced toughness and increased brittleness.
Edge Retention
CruWear and Spyderco SPY27 steels have comparable levels of wear resistance and edge retention.
However, CruWear can achieve even higher edge retention and wear resistance due to higher achievable hardness and higher toughness.
While both steels exhibit comparable edge retention and wear resistance levels, CPM Cruwear’s high toughness and uniform carbide distribution may give it an advantage in terms of overall edge stability under demanding cutting conditions.
The outstanding toughness of CPM Cruwear makes it more resistant to chipping and edge deformation, allowing it to maintain its edge geometry and sharpness for longer periods, even when subjected to significant stress and impact forces.
Toughness
CPM Cruwear exhibits significantly better toughness compared to Spyderco SPY27 steel, which is a crucial property for knives as it determines their resistance to chipping and breakage during use.
Crucible Charpy C notch impact test show that CPM CruWear exhibits an impact toughness of 60ft-lbs at a hardness of 60HRC, SPY27 achieves around 28ft-lbs at 60HRC.
CPM Cruwear micrograph shows a much finer and more evenly dispersed carbide structure compared to the larger carbide clusters present in the SPY27 micrograph.
These larger carbide clusters in SPY27 can act as stress concentration points, making the steel more susceptible to cracking and reducing its overall toughness.
Corrosion Resistance
When it comes to corrosion resistance, SPY27 steel has a distinct advantage over CPM Cruwear due to its stainless steel composition.
SPY27 stainless steel exhibits corrosion resistance similar to other popular stainless steel grades like S30V and S35VN.
The high chromium content in SPY27 knife steel, combined with the right balance of other alloying elements, forms a protective passive layer on the steel’s surface, which acts as a barrier against corrosion.
In contrast, CPM Cruwear is a non-stainless steel, meaning it does not have the same level of corrosion resistance as stainless grades.
While Cruwear contains a relatively high amount of chromium compared to other non-stainless tool steels, its corrosion resistance is only classified as above average.
CruWear cannot match the levels of true stainless steels like CPM SPY27 or 420 stainless steel.
Ease of Sharpening
SPY27 steel has a distinct advantage over CPM Cruwear steel when it comes to ease of sharpening and grinding.
SPY27 was specifically formulated as a knife steel with enhanced grindability and sharpening characteristics in mind.
SPY27 sharpen and grind slightly better than S35VN steel, which is already known for its good sharpening properties.
CPM Cruwear’s grindability is similar to D2 tool steel, albeit slightly better due to the powder metallurgy process.
Micrographs reveal that SPY27 has a somewhat finer and more uniform carbide distribution compared to CPM Cruwear.
This microstructural advantage contributes to better grindability and ease of sharpening for SPY27 over Cruwear.
Finer and more evenly dispersed carbide structure in SPY27 minimizes the risk of excessive abrasive wear on the sharpening media.
Final Thoughts SPY27 vs CruWear Steel
In my opinion, CPM Cruwear blade steel truly shines when it comes to toughness and edge stability.
The outstanding resistance to chipping and edge deformation, makes CPM Cruwear an ideal choice for fixed blades and outdoor knives designed to tackle demanding tasks.
Its impressive toughness allows the blade to withstand significant impact forces and abuse, making it a reliable choice for outdoor enthusiasts and those who subject their knives to heavy-duty use.
On the other hand, SPY27, being an exclusive Spyderco steel, is better suited for pocket knives and folding knives where ease of maintenance and corrosion resistance are priorities.
As a stainless steel, CPM SPY27 offers superior corrosion resistance compared to the non-stainless CPM Cruwear, ensuring that the blade remains protected against moisture and harsh environments.
Additionally, SPY27’s finer carbide structure and composition tailored specifically for knives result in enhanced grindability and sharpening ease, allowing for more efficient edge maintenance and longevity.