By Yashar Mousavand • Lead Instructor
A bushcraft knife is always a compromise between three property systems that push against each other: how long the edge keeps cutting, how well the edge survives shock and lateral loads, and how slowly the steel degrades in wet or salty environments. At Yashar Survival Academy I teach skills as a system (preparation, prevention, response), and knife choice should be treated the same way: define the environment, define the failure mode you cannot accept, then pick steel plus heat treat plus geometry that controls that failure mode. [1]
1) Define the three properties in engineering terms
Edge retention is not one thing
Most knife users talk about “stays sharp,” but edge retention is a mix of at least two mechanisms:
- Wear dominated loss: the apex rounds or abrades away during slicing. This is strongly affected by hardness, carbide type and volume, and the abrasiveness of what you cut. Cutting performance is also strongly influenced by edge geometry and roughness, not just steel. [6]
- Damage dominated loss: micro chipping, apex fracture, or plastic deformation (rolling). This is governed by toughness and edge stability, and it is often the real limiter in wood work with knots or lateral loading. [2]
Edge geometry can dominate steel in controlled tests. Knife Steel Nerds reports an example where changing edge angle from 25 degrees per side to 10 degrees per side produced about a 5x change in edge retention for the same steel. [3]
Toughness is the ability to absorb crack growth energy
For knives, toughness shows up as resistance to micro chipping at the apex under lateral load, fracture at stress concentrators, and crack propagation from small defects.
Knife Steel Nerds summarizes the trade: higher hardness helps avoid rolling, but higher hardness also reduces toughness and increases the chance of chipping. They also note that keeping carbide size and volume fraction small helps maintain toughness at higher hardness. [2]
Corrosion resistance is the stability of the passive surface
In stainless knife steels, corrosion resistance depends on how much chromium (and sometimes molybdenum) is available in the matrix to support a protective passive film. Carbides matter because they can lock chromium up and reduce what is available to protect the surface. Alleima explains that carbides do not prevent corrosion but they tie up chromium. Dissolving enough carbides during hardening releases chromium into the matrix so it can support the passive film, while large primary carbides dissolve less, leaving more chromium locked in carbides and not contributing to corrosion resistance. [5]
2) Why these properties fight each other
The carbide triangle: wear up, toughness down, corrosion often down
If you increase carbide volume and hardness (common in wear focused steels), you often gain abrasive wear resistance, but you pay with toughness. Knife Steel Nerds emphasizes the core trade as how much carbide you want for edge retention without dropping toughness too much. [2][3]
Corrosion can also suffer because carbides consume chromium. Alleima notes that large primary carbides may not dissolve as much during hardening, leaving chromium locked away rather than supporting the passive film. [5]
Heat treat moves you around the triangle even for the same steel
Even with identical chemistry, heat treatment changes microstructure and can shift the balance between retention, toughness, and corrosion behavior.
Concrete stainless example: Alleima 12C27 warns that too low cooling rate after austenitizing leads to carbide precipitation at grain boundaries with the stated consequences of brittleness and reduced corrosion resistance. [4]
Uddeholm adds another important lever: high temperature tempering can precipitate secondary carbides. Uddeholm states this can be detrimental to corrosion resistance but can give somewhat higher wear resistance. [7]
3) Bushcraft reality: which failure mode matters most
In wood, many edge retention complaints are actually toughness or geometry
Wood and knots create lateral loads and stress concentrations at the apex. If your edge loses bite because it micro chips, you did not run out of wear resistance. You exceeded the edge stability your geometry and toughness could support. Higher hardness reduces rolling but increases chipping risk. [2]
In wet environments, corrosion is not cosmetic
Corrosion increases surface roughness and friction, and pits can act as stress concentrators. In humid forest, coastal salt air, or repeated wet sheathing, corrosion resistance is a functional requirement. Microstructure choices that lock chromium into carbides or create chromium depleted zones raise corrosion risk. [4][5]
4) The control knobs you can actually use
Knob 1: Edge geometry, the biggest lever you control
If you only change one variable, change geometry first. Knife Steel Nerds reports an example where edge angle changes produced about a 5x change in edge retention for the same steel. [3]
- A more acute edge can cut longer in abrasion dominated tasks but will be less tolerant of lateral loads.
- A more obtuse edge is much more resistant to chipping and deformation, which is often what bushcraft needs in knots and stop cuts. [2]
- A small micro bevel is a controlled way to trade a little slicing for a large jump in edge stability.
Knob 2: Heat treat targets, the maker’s main lever
If you are evaluating a maker, ask what they control, not what steel they bought. Cooling rate and temper selection can directly affect brittleness and corrosion behavior in martensitic stainless. [4][7]
- Target hardness range and where it is measured.
- Quench and cooling control for stainless steels (to avoid grain boundary carbide issues). [4]
- Tempering regime (temperature and number of tempers) because it shifts toughness and can change corrosion behavior through carbide precipitation. [7]
Knob 3: Surface condition and care, the field lever
In the field, your real corrosion control is time wet, time salty, and time in sheath. Clean and dry beats marketing. If you carry wet blades in closed sheaths, you are manufacturing corrosion regardless of alloy.
5) A bushcraft selection framework that does not rely on steel hype
Use a three step selection logic:
- Define environment: constant wet or coastal salt requires higher corrosion resistance and a toughness margin; dry inland allows more trade space. [5]
- Define dominant edge failure mode: rolling suggests too soft for your angle; micro chipping suggests too hard or too wear focused for your angle, or too much carbide volume for your geometry. [2][3]
- Pick geometry first, then steel and heat treat, because geometry can swing measured retention by multiples. [3][6]
6) A simple test protocol that exposes the triangle
This is practical and repeatable:
- Standardize edge angle and finish on two knives.
- Do controlled carving in seasoned hardwood with stop cuts and notch work. Record micro chipping vs rolling.
- Do a controlled abrasive cut series (cardboard or rope). Track bite loss with the same check each time.
- Do a controlled wet carry cycle (use, wipe, sheath, un sheath next day) and inspect for spotting and pitting.
You Might also Like: Stainless in the Wild: How Heat Treat and Carbides Affect Corrosion Resistance
About the author
Yashar Mousavand is a survival instructor and the founder of Yashar Survival Academy. The Academy focuses on field tested techniques and evidence based guidance to build usable outdoor competence when it matters most. [1]
References
[1] Yashar Survival Academy. About page. https://yashar-survival.ir/en/about-me/
[2] Knife Steel Nerds. What is Edge Stability? https://knifesteelnerds.com/2018/08/27/what-is-edge-stability/
[3] Knife Steel Nerds. My Knife Steel Ratings (edge angle and retention example). https://knifesteelnerds.com/2020/01/13/my-knife-steel-ratings/
[4] Alleima. Alleima 12C27 datasheet PDF. https://www.alleima.com/contentassets/f19934a765084f1c9c5e21081325275b/datasheet-alleima-12c27-en-v2025-05-12-1022-version-1.pdf/download
[5] Alleima. Microstructure and corrosion resistance discussion. https://www.alleima.com/en/knowledge-hub/knife-steel/microstructure/
[6] Materials (MDPI). A Comprehensive Understanding of Knife Cutting. https://www.mdpi.com/1996-1944/16/15/5375
[7] Uddeholm. Heat Treatment of Uddeholm Tool Steels. https://www.uddeholm.com/app/uploads/sites/247/2024/09/Tech-Uddeholm-Heat-treatment-EN.pdf
