M390 vs M398 Knife Steel Comparison

M390 vs. M398: Which Premium Stainless Knife Steel Reigns Supreme?

When it comes to premium knife steels, Böhler-Uddeholm’s M390 has long been a favorite among collectors and enthusiasts for its impressive combination of corrosion resistance, edge retention, and overall high performance. In recent years, another steel from Böhler-Uddeholm—M398—has started to gain attention. This newcomer offers an intriguing twist on M390’s characteristics, potentially pushing the boundaries of edge retention even further. If you’re wondering how these two high-end powdered metallurgy steels stack up against each other, this comprehensive guide is for you.

Below, we’ll explore their compositions, typical hardness ranges, real-world performance, heat-treatment nuances, cost, and ideal uses—plus address some frequently asked questions at the end. Whether you’re interested in heavy slicing, everyday carry (EDC), or professional kitchen scenarios, read on to decide which steel best suits your needs.

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1. M390 Steel: Composition & Key Features

Composition Summary

• Carbon: ~1.9% (sometimes listed 1.8–2.0%)
• Chromium: 20%
• Manganese: 0.3%
• Molybdenum: 1%
• Silicon: 0.7%
• Tungsten: 0.6%
• Vanadium: 4%

M390 is a powdered metallurgy (PM) stainless steel renowned for its balanced performance. Böhler-Uddeholm engineered M390 to offer:

• Extremely high corrosion resistance (rated 9 on a 1–10 scale)
• Above-average toughness (4)
• Excellent edge retention (7)
• Moderately challenging but feasible sharpening effort (5)

Collectors often choose M390 for its “sweet spot” of properties—it’s difficult enough to hold a keen edge for a long time yet not so challenging to sharpen as some more extreme “super steels.”

Typical Hardness (Rockwell C) & Practical Implications

M390 typically hardens in the range of about 60–62 HRC. Some custom knife makers might push it slightly higher (up to ~62–63 HRC) if they’re seeking maximum edge retention, but going too hard can impact toughness. At around 60–62 HRC, most users find an excellent balance between edge stability and durability. Many blades also benefit from a cryogenic step in the heat treatment, which helps convert retained austenite to martensite, enhancing hardness and wear resistance.

Ideal Uses of M390

• Everyday Carry (EDC) Knives: Holds an edge through daily tasks and resists rust with minimal maintenance.
• Outdoor & Bushcraft Knives: High corrosion resistance (9) suits wet or humid climates.
• High-End Chef Knives: Lasting sharpness and stain resistance are prized in professional or home kitchens.

Because M390 combines high rust resistance, solid edge retention, and moderate toughness, it’s considered a versatile choice for users who want a premium stainless steel without venturing into overly specialized territory.

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2. M398 Steel: Composition & Key Features

Composition Summary

• Carbon: 2.7%
• Chromium: 20%
• Manganese: 0.5%
• Molybdenum: 1%
• Silicon: 0.5%
• Tungsten: 0.7%
• Vanadium: 7.2%

Similar to M390, M398 is made using a powdered metallurgy process. However, the higher carbon (2.7%) and vanadium (7.2%) content sets the stage for a steel that can achieve even greater wear resistance. The trade-off is typically lower toughness compared to M390. Although official toughness numbers are not always published, manufacturer data and anecdotal testing agree that M398 prioritizes edge retention above all else. It remains highly corrosion-resistant (thanks to 20% chromium), though it may chip more easily under heavy impact.

Typical Hardness (Rockwell C) & Practical Implications

M398 is often heat-treated to slightly higher hardness ranges than M390—commonly around 61–64 HRC. The possibility of going above 62 HRC can yield remarkable edge-holding capacity, but toughness will decrease further. For those who seek maximum slicing longevity—cutting rope, cardboard, or other fibrous materials—M398 at the upper end of its hardness scale can be extremely effective.

Ideal Uses of M398

• Heavy Slicing Tasks: Repeated cardboard cutting, warehouse use, or bulk rope slicing.
• Advanced EDC Users: Ideal if your daily tasks emphasize cutting performance over toughness.
• High-End Chef/Butcher Knives: Exceptional wear resistance in controlled kitchen environments, provided you avoid hard bone contact.

While M398 can excel at these specific uses, it’s not the first choice for applications requiring higher toughness (like batoning or prying). In short, if you’re comfortable avoiding rough tasks and want to extend time between sharpenings, M398 might be the steel for you.

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3. Detailed Alloy Element Effects

Both M390 and M398 rely on a balanced composition that includes significant amounts of chromium, carbon, and vanadium, among other elements. Below is a quick breakdown:

• Carbon

  • Increases hardness and edge-holding capacity.
  • Higher carbon in M398 leads to higher attainable hardness but can reduce toughness.

• Chromium (20% in both)

  • Essential for stainless properties.
  • At 20%, both steels exhibit excellent rust and stain resistance.

• Vanadium

  • Enhances the formation of very hard vanadium carbides, improving wear resistance and edge stability.
  • M398’s 7.2% vanadium boosts its edge-holding but makes sharpening more demanding and slightly reduces toughness.

• Molybdenum

  • Adds strength at high temperatures and assists in uniform carbide distribution.

• Tungsten & Silicon

  • Tungsten can improve strength, hardness, and wear resistance.
  • Silicon deoxidizes steel during production, with a minor effect on toughness.

• Manganese

  • Aids in deoxidation.
  • Slightly affects hardness penetration during heat treatment.

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4. Heat Treatment Nuances & Forging

M390

M390 is relatively straightforward to heat-treat for metallurgists familiar with high-end stainless steels. It generally does not require extremely specialized steps, though precise protocols help optimize the hardness/toughness balance:

• Cryogenic Treatment: Commonly used to transform retained austenite to martensite.
• Target HRC: Typically 60–62, though some push to 63 for extra edge retention.

M398

Being designed for higher attainable hardness, M398 can be more finicky:

• Precise Temperature Control: Essential to avoid brittleness.
• High Carbon & Vanadium Content: Careful normalizing and stress-relieving cycles reduce warping and cracking risks.
• Cryo Step: Also highly recommended to stabilize the microstructure.

Forging Considerations

Both steels are typically used in stock-removal processes rather than forging because of their high vanadium content:

• M398 Especially Challenging: Its high vanadium content makes forging more difficult and less common.
• Thermal Cycling: Makers must be meticulous to avoid cracks or stress accumulations.

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5. Patina Formation & Protective Coatings

Patina Development

• M390 has a corrosion resistance rating of 9 (on a 1–10 scale). M398 also contains 20% chromium, implying similarly strong stainless properties.
• Neither steel will form a patina easily like high-carbon or tool steels (e.g., 1095, O1, W2).

Protective Coatings

• Rarely necessary purely for corrosion resistance due to their stainless nature.
• Some users still prefer coatings like DLC, PVD, or Cerakote for aesthetics or reduced glare.

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6. Side-by-Side Comparison in Real-World Use

	M390	M398
Hardness Range (HRC)	~60–62	~61–64
Edge Retention	7 (Excellent)	Potentially higher than 7 (Outstanding)
Corrosion Resistance	9 (Very High)	Very High (similar to M390)
Toughness	4 (Moderate)	Likely lower than 4 (Moderate-to-Low)
Ease of Sharpening	5 (Moderate effort)	Harder to sharpen (diamond/CBN recommended)
Notable Advantage	Balanced performance for most tasks	Maximal wear resistance for heavy cutting

Edge Retention

• M390: With an edge retention rating of 7, it already excels in rigorous cutting tasks.
• M398: Higher carbon and vanadium can outlast M390 in extreme cut tests (e.g., cardboard, rope).

Toughness

• M390: Moderate (4). Fairly resistant to chipping from light or moderate impacts.
• M398: Likely lower toughness than M390, making it more prone to chipping or micro-fractures under heavy impact.

Corrosion Resistance

• M390: 9/10, excellent for humid or salty environments.
• M398: Same 20% chromium; in practice, it performs similarly to M390 in everyday scenarios.

Ease of Sharpening

• M390: Rated at 5—challenging but manageable with quality stones.
• M398: More demanding due to higher vanadium carbides, especially above 62 HRC. Diamond or CBN stones are highly recommended.

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7. Which Steel Is Better for Which Tasks?

Bushcraft and Survival

• M390: Tends to be more reliable with moderate toughness—suitable for tasks like feather-sticking or light batoning.
• M398: Exceptional slicing ability but more prone to chipping if you accidentally strike a rock or twist the blade.

EDC (Everyday Carry)

• M390: A perennial favorite due to its balanced properties, especially corrosion resistance and respectable toughness.
• M398: Great if your daily tasks involve heavy cutting of abrasive materials and you’re confident you won’t subject the blade to harsh impacts.

Kitchen Use

• M390: Highly stainless, slightly better toughness if you occasionally tackle small bones.
• M398: Outstanding wear resistance for professional chefs who need extended cutting performance; just avoid bones or very hard materials.

Tactical or Survival Scenarios

• M390: The safer option when you need a blend of edge holding and resilience.
• M398: If slicing performance is paramount and abuse is unlikely, it can be a superb choice.

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8. Cost, Availability & Maintenance

Cost

• Both steels are premium offerings.
• M390: Widely available from major knife brands and custom makers; costs are high but have stabilized.
• M398: Newer, less common, and can be more expensive due to limited supply and the difficulty of working with it.

Availability

• M390: Broad adoption across multiple production knife companies; numerous designs and price points.
• M398: Primarily seen in custom or small-batch runs. It may become more common if more manufacturers invest in it.

Maintenance

• Corrosion Resistance: Both steels require minimal care thanks to high chromium content.
• Sharpening: M398’s higher vanadium content demands rigorous sharpening methods. Using diamond or CBN sharpeners is wise, though M390 also benefits from similar stones for best results.

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9. Pros & Cons

M390

Pros

1. Excellent corrosion resistance (9/10).
2. Very good edge retention (7).
3. Balanced toughness (4) for most everyday or outdoor tasks.
4. Moderate effort to sharpen (5).
5. Widely available with a proven track record.

Cons

1. Not as extreme in wear resistance as some super steels (e.g., M398, Maxamet).
2. Still demands good sharpening equipment (diamond/ceramic) if you want to maintain a super-fine edge.

M398

Pros

1. Potentially superior wear resistance due to higher carbon and vanadium.
2. Exceptionally corrosion-resistant (20% chromium).
3. Ideal for those needing a blade that holds its edge for the longest possible time.

Cons

1. Likely lower toughness, prone to chipping under heavy or lateral stress.
2. More difficult to sharpen, especially above 62 HRC.
3. Less availability and often more expensive due to limited supply.

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10. Final Thoughts & Recommendations

Choosing between M390 and M398 depends on your priorities. If you want a nearly perfect blend of overall performance—high corrosion resistance (9), very good edge retention (7), and moderate toughness (4)—M390 will likely make you happiest. It’s more established, somewhat easier to sharpen (rated 5), and is widely available across many knife models and price points.

On the other hand, if you’re a collector or seasoned user who values maximum wear resistance and doesn’t mind investing in specialized sharpening equipment (and careful handling to avoid heavy impact), M398 may be your ultimate high-end choice. Its high carbon and vanadium content can produce a wickedly long-lasting edge, but you’ll pay for it in reduced toughness and increased difficulty at the sharpening bench.

For bushcrafters, survivalists, and those who push their blades hard: M390’s moderate toughness is probably safer. For professional chefs and heavy slicers seeking to minimize sharpening intervals, M398 could be an enticing option—just be mindful of potential chipping with bones or very hard materials.

Overall, both steels represent top-tier metallurgy. Whether you lean toward M390 or M398, you’ll be getting a premium stainless steel that outperforms most conventional alternatives. Don’t forget: no matter how advanced the steel, proper heat treatment, blade geometry, and user technique are still paramount for an outstanding knife.

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Frequently Asked Questions (FAQ)

Q: How do M390 and M398 compare to other super steels like S90V, S110V, or Maxamet?
A: These steels all occupy the upper echelons of edge performance. M390 and M398 are more stainless than many alternatives, though Maxamet or S110V may beat them in raw wear resistance. However, M390 and M398 are still more than sufficient for most high-end needs and offer strong corrosion resistance where some others may lag.

Q: Is M398 significantly harder to sharpen than M390?
A: Yes, M398’s higher vanadium content and potential for higher hardness generally make it more difficult to sharpen. You’ll likely need diamond or CBN stones to maintain a razor edge without excessive effort.

Q: Does M398 rust more easily than M390 despite its higher wear resistance?
A: Both steels have 20% chromium, so their corrosion resistance is similarly excellent. In normal use, you shouldn’t notice a big difference in rust prevention.

Q: Which steel is better for a professional kitchen?
A: If you’re careful about avoiding hard bones and want maximum edge retention, M398 can be a fantastic choice. M390 is slightly more forgiving if you occasionally apply lateral stress or encounter tougher materials.

Q: Do both steels benefit from cryogenic treatments?
A: Yes. Cryo steps help convert retained austenite to martensite, improving hardness and wear resistance for both M390 and M398.

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Thank you for reading! We hope this breakdown of M390 vs. M398 helps you choose the steel that perfectly suits your cutting style, needs, and preferences. Happy collecting and cutting!

Note: This guide is based on commonly available data from Böhler-Uddeholm product sheets, knife community feedback, and anecdotal testing. Always follow the specific guidance of your knife manufacturer or custom maker for the best results.