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M398 vs CPM S45VN Knife Steel Comparison

M398 vs. CPM-S45VN – A Comprehensive Comparison for Knife Enthusiasts

Knifemaking technology continues to advance, bringing new “super steels” to the market every year. Two that have captured the interest of enthusiasts are Böhler-Uddeholm’s M398 and Crucible Industries’ CPM-S45VN. Both are powdered-metallurgy steels with excellent features for modern blades, yet each offers a unique balance of performance characteristics. In this comprehensive guide, we will explore the chemistry, typical hardness ranges, heat-treatment considerations, and real-world applications of M398 and CPM-S45VN, so you can determine which one best suits your needs.

At a Glance:

Pick M398 if you want maximum edge retention and don’t mind more challenging sharpening.
Pick CPM-S45VN if you prefer a well-balanced blade that’s easier to maintain and offers good toughness.

1. Introduction to M398

M398 is a high-end powdered metallurgy steel created by Böhler-Uddeholm, often regarded as a “hyper-wear-resistant” evolution of the popular M390. It is designed with an emphasis on extreme wear resistance and high hardness while still maintaining very good corrosion resistance. Published compositions can vary slightly, so the following numbers are approximate:

Carbon (C): ~2.6–2.7%
Chromium (Cr): ~20%
Manganese (Mn): ~0.3–0.5%
Molybdenum (Mo): ~1%
Silicon (Si): ~0.5%
Tungsten (W): ~0.6–0.7%
Vanadium (V): ~7.2–8%

Key Performance Snapshot (M398):

Corrosion Resistance: Excellent
Toughness: Fair
Edge Retention: Excellent
Ease of Sharpening: Poor

In essence, M398 takes the wear resistance concept up a level from M390 by increasing both carbon and vanadium content. The result is a steel prized for cutting abrasive materials over long periods without frequent sharpening. However, that same high carbide volume makes it harder to sharpen effectively; diamond or CBN stones are highly recommended.

2. Introduction to CPM-S45VN

CPM-S45VN is an evolution of Crucible’s S30V/S35VN series, aiming to refine the well-known balance of toughness, corrosion resistance, and edge retention. Its composition typically includes:

Carbon (C): 1.48%
Chromium (Cr): 16%
Molybdenum (Mo): 2%
Vanadium (V): 3%
Niobium (Nb): 0.5%
Nitrogen (N): 0.15%

Key Performance Snapshot (CPM-S45VN):

Corrosion Resistance: Excellent
Toughness: Good
Edge Retention: Good
Ease of Sharpening: Good

Compared to M398, CPM-S45VN is more well-rounded. It retains a keen edge without compromising ease of maintenance or toughness. While it may not achieve the “extreme” wear resistance of M398, it remains sufficiently durable and more approachable to sharpen—making it an excellent choice for everyday carry (EDC) and other versatile uses.

3. Typical Hardness (Rockwell C) Ranges and Practical Implication

M398: Commonly hardened in the 60–64 HRC range. At the higher end (62+ HRC), M398 achieves its legendary wear resistance but may sacrifice some toughness. Careful use is advised to avoid chipping.
CPM-S45VN: Generally falls in the 60–62 HRC range, though specialized heat treatments can push it closer to 63 HRC. This sweet spot provides a balanced profile of toughness, edge retention, and ease of sharpening.

For those seeking a “laser-like” slicer with minimal downtime between sharpenings, M398 at higher hardness rates can be a real game-changer. If you value a more balanced steel that’s still impressively sharp yet easier to maintain, CPM-S45VN around 60–61 HRC is an excellent pick.

4. Detailed Alloy Element Effects

Below is a quick look at how key elements in these steels affect their core properties:

Carbon (C): Increases hardness and edge retention. M398’s higher carbon (~2.7%) significantly boosts wear resistance but also increases sharpening difficulty.
Chromium (Cr): Enhances corrosion resistance and helps form chromium carbides. With ~16% in S45VN and ~20% in M398, both have strong stainless properties.
Vanadium (V): Greatly improves wear resistance by producing extremely hard vanadium carbides. M398’s ~7–8% V is a key factor in its remarkable edge retention; S45VN’s 3% balances strength and sharpenability.
Molybdenum (Mo): Improves pitting resistance and can aid toughness by refining the steel’s grain structure.
Niobium (Nb) in S45VN: Forms small, stable carbides, enhancing grain refinement, toughness, and corrosion resistance.
Tungsten (W) in M398: Works in tandem with vanadium carbides to further boost wear resistance, especially in high-friction or abrasive cutting tasks.

5. Heat-Treatment Nuances and Forging

M398: Due to its extremely high carbide volume, M398 can be tricky to heat treat. Achieving optimal hardness without sacrificing all toughness often involves carefully controlled soak times, multi-step quenching, and precise tempering. Warping or cracking can occur if temperature parameters are not managed meticulously.
CPM-S45VN: Similar to other CPM steels, it benefits from precise austenitizing temperatures and sometimes a cryogenic treatment to maximize hardness and refine carbides. However, S45VN is generally considered more forgiving to heat treat than M398.

Both steels are commonly used in stock-removal knife making due to their high carbide content and the difficulty of forging them at high temperatures. Most bladesmiths opt for precision grinding or CNC milling over traditional forging.

6. Side-by-Side Comparison Table

	M398	CPM-S45VN
Corrosion Resistance	Excellent	Excellent
Toughness	Fair	Good
Edge Retention	Excellent	Good
Ease of Sharpening	Poor (difficult to sharpen)	Good (relatively easier)
Typical HRC Range	~60–64	~60–62 (can reach 63 with specialized HT)
Primary Strength	Extreme wear resistance	Well-rounded performance

7. Real-World Applications and Ideal Uses

Bushcraft and Survival: These activities demand a tough steel that can withstand impacts and prying. M398’s fair toughness might not suit repetitive hard impacts like batoning. S45VN, with better toughness, often provides a more reliable experience for wilderness tasks.
Everyday Carry (EDC): For those who need a versatile blade for typical tasks—opening boxes, light food prep, etc.—S45VN’s balance of edge retention, toughness, and easier sharpening is ideal. M398 is attractive if you frequently cut very abrasive materials (e.g., fibrous textiles, high volumes of cardboard) and require the longest possible edge life.
Kitchen Use: Both steels resist rust effectively. M398’s outstanding wear resistance can handle lengthy prep sessions without dulling, but any chipping can be laborious to fix. S45VN is more forgiving for general kitchen duties and simpler to maintain with standard sharpening tools.
Survival/Tactical: In demanding conditions, reliability is paramount; S45VN’s more robust toughness and quicker resharpening can be reassuring. Meanwhile, M398’s extreme wear resistance is beneficial if you won’t have the opportunity to sharpen often—just be aware of its chipping risk under lateral stress.

8. Ease of Sharpening and Maintenance

M398: Its extremely high carbide content makes it notoriously difficult to sharpen. Diamond or CBN stones are almost mandatory to effectively abrade the hardened carbides. When sharpened correctly, though, M398 holds its edge for a very long time.
CPM-S45VN: Less daunting to sharpen, S45VN can be maintained with good-quality aluminum oxide or diamond stones. It tolerates minor technique errors more gracefully and small chips or dull spots are easier to remedy.

In terms of corrosion resistance, both are classified as “excellent.” Simple cleaning after use and thorough drying will help maintain a pristine finish.

9. Patina Formation and Protective Coatings

Because both steels are stainless with high chromium content, they do not form a classic patina like 1095 or W2 carbon steels. In exceptionally corrosive conditions, minor staining could occur, but rust formation is unlikely if basic care is practiced.

Some knife enthusiasts opt for coatings like DLC (Diamond-Like Carbon) or PVD (Physical Vapor Deposition) for added surface hardness or aesthetic reasons. These coatings won’t harm performance but usually aren’t essential given these steels’ robust corrosion resistance.

10. Cost, Availability, and Market Reputation

Cost: Both M398 and CPM-S45VN are premium steels. M398 can be pricier due to its specialized nature and relative rarity. S45VN is also premium but more commonly found thanks to the success of the CPM line (S30V, S35VN, etc.).
Availability: CPM-S45VN is increasingly common among production knife brands aiming for a high-performance EDC. M398 is more limited and often appears in custom or small-batch production runs, given its niche appeal and demanding machinery requirements.
Reputation: M398 is revered among enthusiasts as an “edge retention monster” for hardcore slicing tasks. CPM-S45VN enjoys a reputation as a versatile steel that’s easy to sharpen compared to many other “super steels,” solidifying it as a go-to option for general-purpose use.

11. Pros and Cons

M398

Pros:

Extraordinary edge retention (excellent wear resistance)
Excellent corrosion resistance
Ideal for extended cutting of abrasive or fibrous materials

Cons:

Fair (not high) toughness
Challenging to sharpen without specialized equipment
Higher price point and less availability

CPM-S45VN

Pros:

Excellent corrosion resistance
Good combination of toughness and edge retention
Easier to sharpen compared to M398
More readily available for EDC and kitchen knives

Cons:

Not as wear resistant as M398
Still a premium-priced steel

12. Why Choose One Over Other Steels?

M398:
- Best for users who prize maximum edge retention above all else.
- Highly effective for extended cutting and minimal downtime.
- Demands advanced sharpening tools (diamond/CBN) and technique.
CPM-S45VN:
- Ideal for those who want a balanced steel—good edge retention, good toughness, and easier maintenance.
- Suited for a wider range of tasks, from EDC to the kitchen.
- Less finicky about sharpening methods than M398.

For added context, M398 can be considered a “next-level” or more specialized version of M390, while CPM-S45VN refines the proven S30V/S35VN formula by leveraging niobium-carbide technology.

13. Summary of Key Takeaways & Final Recommendations

M398 and CPM-S45VN are both premium powdered-metallurgy steels offering excellent corrosion resistance. M398 excels in top-tier edge retention thanks to its high carbon and vanadium content, making it a powerhouse for slicing abrasive materials. However, it has fair toughness and can be unforgiving when sharpening or using thin edge geometries.

On the other hand, CPM-S45VN strikes a more balanced profile: good toughness, good edge retention, and relatively straightforward maintenance. This makes it an attractive all-around steel for various applications—EDC, kitchen knives, bushcraft, and more—while acknowledging it doesn’t quite reach M398’s wear-resistance peak.

Choose M398 if:

You require a blade capable of very long cutting sessions on abrasive materials.
You have mastered the art of sharpening high-carbide steels (and own diamond or CBN stones).
You prioritize wear resistance over ease of maintenance.

Choose CPM-S45VN if:

You need a versatile, stainless steel that’s easier to sharpen day-to-day.
You appreciate a strong compromise between edge retention and toughness.
You want a go-to EDC or multi-purpose blade for a variety of cutting tasks.

Both steels represent the cutting edge of modern knife metallurgy. If maximum edge retention is your top priority, M398 might be the ultimate choice. If you prefer an all-rounder that remains user-friendly and dependable, CPM-S45VN is an excellent fit.

Optimal Edge Geometry and Final Tips

M398: Thinner edges excel in slicing but can chip if toughness is pushed too far. If you anticipate harder impacts, consider a slightly thicker grind.
CPM-S45VN: More forgiving for thinner grinds, though still wise to match your edge geometry to your usage (e.g., thicker edges for bushcraft, thinner for fine slicing).