MagnaCut vs M390

MagnaCut is a relatively new powder metallurgy stainless steel developed by Dr. Larrin Thomas and produced by Crucible Industries as CPM MagnaCut. 

M390 is an established high-performance stainless steel originally created by Bohler and also produced as 20CV by Crucible and 204P by Carpenter.

While both are excellent knife steels, MagnaCut represents a leap forward in properties and performance compared to traditional steels like M390.

By optimizing the carbide structure and fully eliminating chromium carbides, MagnaCut achieves a better combination of corrosion resistance, and most importantly toughness over M390.

For toughness-critical applications from EDC folders to large fixed blades, MagnaCut provides an advantage over M390 and other steels with high chromium carbide content.

MagnaCut with its well-rounded properties makes a strong case as the best all-around stainless steel available today for knife making.

CPM MagnaCut vs M390 Steel At A Glance

Hardness

Hardness is a steel’s resistance to wear and deformation, it is a crucial property for knife performance. MagnaCut and M390 can achieve high hardness over 63 HRC with proper heat treatment.

M390 may be able to reach slightly higher hardness up to 64 HRC with optimized heat treatment, but MagnaCut can maintain its hardness at higher austenitizing temperatures.

With cryogenic processing, MagnaCut can readily reach 65 HRC while M390 would require very specific heat treating to exceed 64 HRC.

Both M390 and MagnaCut steels exhibit excellent hardness through their high alloy content and carbide reinforcement. This high hardness translates to good edge retention and resistance to abrasion.

For most applications, the small differences in achievable hardness between MagnaCut and M390 will not make a major difference in real-world cutting ability. 

Toughness

Toughness is the ability of a material to resist shock, chipping, breakage, on impact. MagnaCut steel has significantly higher toughness compared to M390 steel due to its microstructure. 

By eliminating chromium carbides, MagnaCut achieves a fine dispersion of vanadium and niobium carbides resulting in a toughness similar to non-stainless steels like CPM-4V. 

Independent testing shows MagnaCut reaching toughness values over 30 ft-lbs in Charpy impact testing, comparable to CPM-4V and far exceeding steels like M390 and S30V which have coarse chromium carbides.

The high toughness of MagnaCut is an important advantage as it allows for thinner and more acute edge angles to be used without the risk of chipping or micro-fractures for knives. 

The relatively low toughness of M390 limits its use in very thin or highly stressed knife-cutting applications.

MagnaCut represents a major improvement in combining high toughness with good edge retention and corrosion resistance. 

For toughness-critical applications across a range of knife designs, MagnaCut would be the preferred choice over M390 stainless tool steel.

Edge Retention

MagnaCut and M390 have comparable edge retention, with M390 having a slightly better edge retention than Magnacut.

Edge retention is a measure of a steel’s ability to resist abrasion and wear during cutting. It depends on hardness, carbide volume and type, and microstructure.

M390 derives its edge retention from a high volume of chromium-rich carbides, giving it excellent abrasion resistance though at the expense of toughness.

Independent testing shows M390 has 5-10% better edge retention than MagnaCut in standardized tests like CATRA testing. 

MagnaCut still has good edge retention from its vanadium and niobium carbides, just slightly less than M390. For most cutting tasks, the difference in edge retention between the two knife steels would not be noticeable. 

M390 would be preferred only in situations where maximum wear resistance is critical. In general use, MagnaCut matches or exceeds M390’s cutting ability due to better toughness allowing thinner edge angles.

Corrosion Resistance

MagnaCut has better corrosion resistance compared to M390 due to its lack of chromium carbides in the microstructure.

Independent testing shows that MagnaCut resists corrosion as well or better than premium stainless steels like 20CV and S45VN. 

The corrosion resistance of CPM MagnaCut approaches that of excellent stainless steels like Vanax and LC200N. 

The improved corrosion is attributed to having more chromium evenly distributed in the steel matrix rather than tied up in chromium carbides.

In contrast, M390 forms significant chromium carbides during heat treatment which creates chromium-depleted regions vulnerable to corrosion.

While the corrosion resistance of M390 is reasonably good compared to lower alloy steels, MagnaCut represents a clear improvement through its optimized microstructure.

For most applications, especially those involving wet environments, MagnaCut would be preferred over M390 when corrosion resistance is a priority.

However, for purely dry applications where corrosion is not a factor, the slight edge retention advantage of M390 may make it preferable.

Ease of Sharpening

MagnaCut steel has a slight advantage over M390 steel in terms of ease of sharpening. This is attributed to the difference in carbide composition and refinement between the two steels.

MagnaCut contains fine vanadium and niobium carbides which are harder than most sharpening abrasives like aluminum oxide.

M390 contains a high volume of softer chromium-rich carbides that are easier to abrade and remove during sharpening.

However, MagnaCut’s carbides are also very finely dispersed compared to the coarser chromium carbides in Bohler M390. 

This fine carbide structure means there are fewer carbide “bits” that need to be removed in MagnaCut, improving ease of sharpening.

Independent feedback from knifemakers indicates MagnaCut is moderately easier to sharpen than premium stainless steels like S35VN and S45VN which have lower carbide content.

M390 is also reported to be relatively easy to sharpen for its level of wear resistance. However, the fine carbide size of MagnaCut still gives it a minor advantage in sharpening, allowing sharp edges to be produced with less abrasive wear.

For most sharpeners, the difference may not be highly noticeable, but is still an improvement.

Final Thoughts on MagnaCut vs M390

In the past, steels like Bohler M390 offered great hardness and edge retention but at the cost of relatively low toughness.

With the development of MagnaCut powder metallurgy steel, we now have a blade steel that provides an optimal combination of all three.

MagnaCut matches or exceeds M390 in corrosion resistance while also improving on toughness dramatically. This allows MagnaCut knives to use thinner and sharper edges with less risk of chipping or rolling.

MagnaCut retains nearly the same level of edge retention as industry standards like M390 and S90V blade steels. 

While those steels are still better for pure abrasion resistance, MagnaCut holds an overall edge better in real cutting tasks by having the ideal toughness.

MagnaCut would be better for most knife applications, though M390 may be preferred when maximum wear resistance is the priority. The finer carbides also make MagnaCut somewhat easier to sharpen.

Overall, MagnaCut represents an advancement in properties over M390, offering a better balance of wear resistance, toughness, and corrosion resistance.