K390 vs CPM S110V Knife Steel Comparison

K390 vs. CPM-S110V – A Comprehensive Comparison for Knife Enthusiasts

When it comes to high-performance knife steels, two names that often spark debate among enthusiasts are Böhler-Uddeholm K390 and Crucible’s CPM-S110V. Both are prized for their advanced metallurgical properties and exceptional cutting performance. In this comprehensive guide, we’ll compare K390 and CPM-S110V across a range of practical considerations—chemical composition, heat treatment, toughness, edge retention, corrosion resistance, ease of sharpening, and more. By the end, you’ll have a clear understanding of what makes each steel stand out and how to choose the one best suited for your specific needs.

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1. OVERVIEW OF K390

K390 is a premium powder-metallurgy tool steel developed by Böhler-Uddeholm. It is engineered to excel in wear resistance and edge retention, making it a favorite among those who push their knives to extreme cutting tasks.

• Chemical Composition (Approx.)

• Carbon (C): 2.47%
• Chromium (Cr): 4.2%
• Molybdenum (Mo): 3.8%
• Vanadium (V): 9%
• Tungsten (W): 1%
• Cobalt (Co): 2%
• Manganese (Mn): 0.4–0.7% (may vary by data sheet)
• Silicon (Si): 0.55%

K390’s high carbon content (~2.47%) and substantial vanadium (~9%) contribute significantly to its excellent edge retention and overall wear resistance. Its chromium content (~4.2%) is below the ~13% mark typically needed for stainless classification, so K390 only offers fair corrosion resistance.

• Heat Treatment Range

Typical hardness levels for K390 range from around 60 to 64 HRC, depending on the specific heat treatment. Most knife makers opt for ~61–63 HRC to balance hardness with durability.

• Key Performance Characteristics

• Corrosion Resistance: Fair (not stainless)
• Toughness: Good (for a high-alloy steel)
• Edge Retention: Excellent
• Ease of Sharpening: Fair (and often slightly easier than CPM-S110V)

K390 is featured in certain Spyderco models (e.g., Delica 4, Endura 4, Police 4 in K390) and is also popular among custom knife makers who want top-tier wear resistance with decent toughness.

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2. OVERVIEW OF CPM-S110V

CPM-S110V is a high-end stainless tool steel produced by Crucible using powder metallurgy. Known for its potent combination of wear resistance and strong corrosion resistance, CPM-S110V caters to those who prioritize edge longevity in wet or corrosive environments.

• Chemical Composition (Approx.)

• Carbon (C): 2.8–2.9%
• Chromium (Cr): ~15.25%
• Vanadium (V): ~9.1%
• Niobium (Nb): 3%
• Molybdenum (Mo): 2.25%
• Cobalt (Co): 2.5%
• Manganese (Mn): 0.4%
• Silicon (Si): 0.6%
• Tungsten (W): ~0.7% (some data sheets may show as low as 0.2%)

With around 15.25% chromium, CPM-S110V meets the requirements for stainless steel, delivering excellent corrosion resistance. Its high carbon (~2.9%) and vanadium (~9%) contents yield very high wear resistance, though at the cost of moderate toughness.

• Heat Treatment Range

CPM-S110V typically reaches a hardness between 60 and 63 HRC. Achieving peak hardness (around 62–63 HRC) maximizes wear resistance, though some makers might temper it slightly lower to improve toughness.

• Key Performance Characteristics

• Corrosion Resistance: Excellent (stainless)
• Toughness: Fair
• Edge Retention: Very Good
• Ease of Sharpening: Fair to Difficult (due to niobium carbides)

You’ll commonly see CPM-S110V in high-end production knives like Spyderco’s “Blurple” series (Paramilitary 2, Manix 2, etc.) and in custom blades where rust resistance is a priority.

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3. TYPICAL HARDNESS (ROCKWELL C) RANGES & PRACTICAL IMPLICATIONS

• K390: ~60–64 HRC
  Blades at the higher end of this range offer remarkable edge stability but may be more prone to chipping if misused. Many makers settle around 61–63 HRC.

• CPM-S110V: ~60–63 HRC
  Hardness around or above 61 HRC results in exceptional edge retention. However, going too high can reduce toughness, so 62–63 HRC is common in premium knives.

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4. DETAILED ALLOY ELEMENT EFFECTS

• Carbon (C): Increases hardness and wear resistance. Both steels have notably high carbon.
• Chromium (Cr): Enhances corrosion resistance above ~13%. CPM-S110V’s ~15% Cr makes it stainless, whereas K390’s 4.2% Cr does not.
• Vanadium (V): Forms extremely hard vanadium carbides, boosting wear resistance and edge retention. Both steels have high vanadium.
• Molybdenum (Mo): Aids strength at high temperatures and improves hardenability.
• Tungsten (W): Contributes to wear resistance and refines grain structure; K390 has more W (~1%) than S110V.
• Cobalt (Co): Improves hardness and strength, especially under high temperatures.
• Niobium (Nb) (in CPM-S110V): Creates niobium carbides, further enhancing wear resistance without drastically sacrificing toughness.

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5. HEAT-TREATMENT NUANCES AND FORGING

Both K390 and CPM-S110V are powder-metallurgy steels that typically favor stock removal methods rather than traditional forging. They demand precise heat-treat protocols:

• K390: Requires accurate preheating, austenitizing above ~1100°C (2012°F), and controlled tempering cycles. Improper steps can lead to warping or brittleness.
• CPM-S110V: Similar high-temperature austenitizing is required, often followed by cryogenic treatment to convert retained austenite to martensite. Mistakes in quenching or tempering can cause micro-cracks or excessive brittleness.

Because of their high alloy content, both steels are more susceptible to warping and cracking if the heat treatment is not tightly controlled.

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6. SIDE-BY-SIDE PERFORMANCE COMPARISON

6.1 Edge Retention

• K390: Excellent edge retention, frequently lauded for its ability to stay sharp under heavy, prolonged use.
• CPM-S110V: Very good edge retention—close to K390; in many real-world tests, they perform similarly, though K390 may edge it out in extreme wear scenarios.

6.2 Toughness

• K390: Good toughness for such a high-carbide steel. It can handle everyday and some heavy-duty tasks.
• CPM-S110V: Fair toughness. It’s more prone to chipping under shock or lateral stress than K390.

6.3 Corrosion Resistance

• K390: Fair; definitely not stainless. It can develop rust or patina if neglected.
• CPM-S110V: Excellent; ~15.25% Cr enables it to resist corrosion in humid, salty, or wet conditions.

6.4 Ease of Sharpening

• K390: Fair—still requires diamond or ceramic abrasives, but typically considered a touch easier to sharpen than S110V.
• CPM-S110V: Fair/Difficult—a very high volume of hard carbides (including niobium) means diamond/CBN stones are almost a must.

6.5 Wear Resistance and Chipping Risk

• K390: Extremely high wear resistance; can chip if used improperly (e.g., prying) or if the edge is thinned excessively.
• CPM-S110V: Similarly high wear resistance; chipping can be an issue if you place lateral stress on the edge or run an excessively thin geometry.

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7. IDEAL USES OF THESE KNIFE STEELS

K390

• Bushcraft and Outdoor Use: Outstanding for carving, feather-sticking, and other repeated cutting tasks—though you’ll need to monitor for rust.
• EDC (Everyday Carry): Ideal for heavy cutting needs and for users willing to maintain a non-stainless steel.
• Survival or Tactical: Good long-term edge holding in the field, but remember to keep it oiled or waxed to avoid corrosion.

CPM-S110V

• EDC in Corrosive Environments: If you’re around saltwater or high humidity, S110V’s corrosion resistance is a major plus.
• Kitchen Knives: Its stainless property is valuable in the kitchen, where frequent contact with water, acids, and food juices is common.
• High-End Folding Knives: Collectors appreciate the polished look and “like-new” finish over time.

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8. COST, AVAILABILITY, AND MAINTENANCE

• Cost:
  Both steels command premium price points due to complex production and specialized properties.
• Availability:
  • K390: Often found in limited or sprint runs (e.g., Spyderco’s K390 series) and among custom makers.
  • CPM-S110V: Available in popular production models (e.g., Spyderco “Blurple” Paramilitary 2, Manix 2, Native) and in custom offerings.
• Maintenance:
  • K390: Prone to patina or rust; needs regular cleaning and possibly a light coat of oil.
  • CPM-S110V: Much less demanding; a simple wipe-down is typically enough due to its stainless nature.

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9. PATINA FORMATION AND PROTECTIVE COATINGS

• K390:
  Low chromium content (~4.2%) means it can form a natural patina. For many users, this patina is aesthetically pleasing and offers mild corrosion protection. If neglected, though, active rust can develop. Where desired, some makers apply coatings (DLC, Cerakote, etc.) to reduce corrosion.

• CPM-S110V:
  With ~15.25% chromium, it generally remains shiny and rust-free. Patina formation is nearly nonexistent. Coatings are usually not necessary beyond aesthetics.

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10. COMPARISON TABLE

Attribute	K390	CPM-S110V
Corrosion Resistance	Fair (will rust without care)	Excellent (stainless)
Toughness	Good	Fair
Edge Retention	Excellent	Very Good
Ease of Sharpening	Fair (slightly easier)	Fair (often more challenging)
Typical Hardness (HRC)	~60–64	~60–63
Patina Formation	Yes (develops patina)	No (stays bright)
Ideal Uses	Outdoor, bushcraft, EDC	Wet/humid EDC, kitchen, folders

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11. PROS AND CONS

K390 Pros

• Exceptional edge retention and wear resistance
• Good toughness for a high-carbide steel
• Forms an attractive patina (if you like that look)
• Highly sought after by performance enthusiasts

K390 Cons

• Requires vigilant maintenance to prevent corrosion
• Can be challenging to sharpen without proper abrasives
• Less common in some mass-market knife lines

CPM-S110V Pros

• Excellent corrosion resistance
• Very good edge retention, with a clean, polished look
• Found in multiple popular production models
• Lower maintenance concerns regarding rust

CPM-S110V Cons

• Sharpening can be more demanding due to niobium carbides
• Fair toughness—less forgiving under heavy lateral stress
• Premium pricing that can be a barrier

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12. SUMMARY AND RECOMMENDATIONS

Both K390 and CPM-S110V sit at the upper echelon of knife steel performance. Their high wear resistance, strong edge retention, and specialized heat-treat requirements make them staples in high-end folding knives, bushcraft blades, and premium kitchen knives.

• Choose K390 if:

  • You want top-tier edge retention with decent toughness.
  • You don’t mind or even prefer a patina on your blade.
  • You’re willing to maintain a non-stainless steel carefully.

• Choose CPM-S110V if:

  • You need excellent corrosion resistance, such as in coastal or humid climates.
  • You appreciate a lower-maintenance, stainless blade.
  • You want a steel that looks “like-new” longer.

Ultimately, geometry, heat treatment, and usage habits also affect how these steels perform. If you can handle the maintenance, K390’s toughness and wear resistance might appeal to you. If rust prevention and minimal upkeep are key, CPM-S110V shines.

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FINAL THOUGHTS

K390 and CPM-S110V are cornerstones of the modern “super-steel” landscape. Each caters to different usage priorities—K390 excels with exceptional edge retention and decent toughness but requires more maintenance, while CPM-S110V offers robust edge-holding and industry-leading corrosion resistance. Whichever you choose, ensure it’s properly heat-treated and sharpened. Experimentation is part of the joy for knife enthusiasts: discover how each steel’s unique capabilities elevate your cutting experience.

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FREQUENTLY ASKED QUESTIONS (FAQ)

1. Is K390 stainless?
   No. With only about 4.2% chromium, K390 falls well below the ~13% threshold for stainless steels.

2. Which steel is easier to sharpen, K390 or CPM-S110V?
   Both can be challenging, but many users find K390 slightly easier due to having fewer niobium carbides. High-quality diamond or ceramic abrasives are recommended for both steels.

3. What are some real-world knives using these steels?

   • K390: Spyderco’s Delica 4, Endura 4, Police 4 in K390 editions.
   • CPM-S110V: Spyderco’s “Blurple” Paramilitary 2, Manix 2, Native 5, and other high-end folders.

4. How do I prevent rust on K390 blades?
   Regularly clean and dry your blade, apply a light coat of oil or protective wax, and store it in a dry environment.

5. Which steel is better for kitchen use?
   CPM-S110V generally performs better in the kitchen setting due to its excellent stainless properties, whereas K390 needs extra care around moisture and acids.

Regardless of your choice, both K390 and CPM-S110V represent the pinnacle of modern knife steel technology. By matching the steel’s strengths to your environment and cutting needs, you can find a blade that truly excels in your daily (or extreme) tasks.