CPM Cru-Wear is produced by Crucible Industries, while M390 is a product of the Austrian company Böhler.
One of the key differences between these two blade steels lies in their edge retention capabilities.
M390 with its high carbide volume and vanadium content, outperforms CPM Cru-Wear in terms of edge-holding ability, making it a top choice for knives and tools that demand exceptional wear resistance.
However, CPM Cru-Wear excels in toughness, exhibiting values more than twice as high as M390, making it a preferred option for applications where impact resistance and durability are crucial factors.
CPM Cru-Wear and M390 are developed through powder metallurgy production that offer better properties than conventional steels.
This article focuses specifically on the CPM version of Cru-Wear produced by Crucible Industries.
CPM Cru-Wear benefits from the advantages of the Crucible Particle Metallurgy (CPM) process, resulting in a more homogeneous and refined microstructure.
CruWear vs M390 Steel At A Glance
| Property | CPM CruWear Steel | M390 Steel |
|---|---|---|
| Hardness | Aim hardness around 62 HRC | Can achieve hardness up to around 66 HRC |
| Edge Retention/Wear Resistance | Good edge retention but lower than M390. | Excellent edge retention |
| Toughness | Exhibits exceptional toughness, more than twice that of M390 | Relatively low toughness. |
| Corrosion Resistance | Non-stainless steel, low corrosion resistance. | Highly corrosion-resistant stainless steel. |
| Ease of Sharpening | Slightly easier to sharpen than M390 | Lower than CPM CruWear |
Toughness
CPM CruWear exhibits significantly higher toughness compared to M390 steel.
The toughness testing data from Crucible shows that at around 60 HRC hardness, CPM Cru-Wear achieved impact toughness values in the range of 60 ft-lbs, which is exceptionally high for a high-alloy tool steel.
On the other hand, information on M390 indicates that it has relatively low toughness, with values around 8-9 ft-lbs at 62 HRC, which is more typical for a high-carbide, wear-resistant steel like M390.
CPM Cru-Wear exhibits exceptional toughness, more than twice that of M390 steel, despite both being high-alloy, wear-resistant steels.
The high toughness of CPM Cru-Wear makes it advantageous for knife applications where impacts and elevated stress levels may be encountered, while still providing good wear resistance.
In contrast, the relatively low toughness of M390, though acceptable for knives without thin edges or high stress levels, limits its suitability for such demanding applications knives.
Hardness
Bohler M390 steel has a higher potential maximum hardness compared to CruWear Steel.
The data sheet for CPM Cru-Wear shows an aim hardness of around 62 HRC when heat treated at 1950°F (1065°C) and triple tempered at 1000°F (540°C).
On the other hand, the M390 data sheet from Böhler indicates the ability to achieve hardness values up to around 66 HRC, depending on the tempering temperature and whether subzero treatment is applied or not.
The higher achievable hardness of M390 potentially translate to better edge retention in knives made from this steel, although other factors like carbide volume and composition also play a role.
Edge Retention
In terms of edge retention and wear resistance, M390 steel demonstrates superior performance compared to CPM Cru-Wear.
M390 achieves its exceptional edge retention capability primarily through its high carbide volume, comprising approximately 22% carbides.
M390 contains a significant proportion of hard vanadium carbides, along with chromium carbides, which contribute to its excellent wear resistance.
The high vanadium content in M390 plays a crucial role in forming these hard vanadium carbides, enhancing its edge-holding ability.
While CPM Cru-Wear also derives its wear resistance from vanadium carbides, its carbide content is lower than M390, resulting in relatively lower edge retention.
Crucible data sheet indicates that CPM Cru-Wear offers better wear resistance than AISI D2 but approaches the level of AISI M2, which has a lower carbide volume compared to M390.
The superior edge retention of M390 knife steel translates into longer-lasting cutting edges, reducing the need for frequent sharpening, and enhancing the overall performance and longevity of knives made from this steel.
However, it is important to note that the exceptional edge retention of M390 comes at the cost of reduced toughness compared to CPM Cru-Wear, as mentioned earlier.
Corrosion Resistance
Bohler M390 was made as a stainless steel with high wear resistance, CPM Cru-Wear on the other hand is a non stainless tool steel.
M390 steel exhibits significantly higher corrosion resistance compared to CPM Cru-Wear, making it a more suitable choice for knife applications where corrosion resistance is a critical factor.
As a martensitic chromium steel with approximately 20% chromium content, M390 falls into the category of highly corrosion-resistant stainless steels.
The high chromium content in M390 promotes the formation of a passive oxide layer, which acts as a barrier against corrosive environments, thereby enhancing its corrosion resistance.
While CPM Cru-Wear does contain some chromium (around 7.5%), this level is insufficient to classify it as a stainless steel, and its corrosion resistance is expected to be relatively low compared to M390.
The superior corrosion resistance of M390 places it in the range of highly corrosion-resistant steels like S110V.
This makes M390 a favorable choice for knives that may be exposed to harsh environments, moisture, or corrosive substances, as it will better withstand rusting and corrosion compared to CPM Cru-Wear.
Ease of Sharpening
CPM Cru-Wear holds an advantage over M390 stainless steel in terms of ease of sharpening and grindability.
The machinability of CPM Cru-Wear when in an annealed state is comparable to that of D2 tool steel, but its ability to be grind or abraded is slightly superior.
The enhanced grindability of Cru-Wear Steel extends to the sharpening process as well.
When using aluminum oxide abrasives for sharpening, CPM Cru-Wear exhibits better ease of sharpening compared to M390.
This can be attributed to the presence of lower volume of carbides in CPM Cru-Wear than the carbides found in M390.
However, it’s important to note that when sharpening with harder abrasives like diamond or cubic boron nitride (CBN) stones, the ease of sharpening would be comparable between CPM Cru-Wear and M390, as these abrasives are harder than the carbides present in both steels.
Final Thoughts on CruWear vs M390 Steel
In my experience working with both of these blade steels, I’ve found that each offers its own set of advantages depending on the specific application.
M390, developed by Bohler, truly lives up to its reputation for exceptional edge retention and high wear resistance.
The high vanadium content and significant carbide volume in M390 result in edges that can maintain their sharpness for impressively long periods, even under demanding use.
This makes M390 an excellent choice for knives and tools where maximum edge retention is the top priority.
However, I would recommend Cru-Wear for applications where a more balanced combination of properties is desired.
While not quite matching M390 edge retention, Cru-Wear still offers very good wear resistance that outperforms many conventional tool steels like D2.
What sets Cru-Wear apart is its exceptional toughness and slightly easier sharpening characteristics when using aluminum oxide abrasives.
This balance of properties allows for thinner edge geometries on Cru-Wear knives without compromising toughness, contributing to improved cutting performance.