Whether a steel is "better" than D2 depends on what you need it to do—D2 is a great, affordable tool steel with fantastic wear resistance, but it can be brittle and is prone to rusting.
The correct choice depends on the failure mode. If the part fails due to wear, D2 is usually the better direction. If the part fails by cracking, bending, fatigue, or impact, 4140 is usually the safer choice.
Disadvantages of D2 Steel
Although D2 contains chromium, it is not fully stainless, which means it can rust if not properly maintained, especially in humid conditions. The hardness that contributes to D2's edge retention can also make sharpening difficult, particularly for beginners.
For best performance, we harden to a Rockwell hardness of RC 58-61. When choosing a blade steel, knife buyers should consider that D2 can be more difficult to sharpen when compared to 420HC because it's a harder steel. However, it will maintain an edge and stay sharper longer.
Neither is universally "better"; it depends entirely on your needs. D2 is harder and holds an edge longer, but is semi-stainless and harder to sharpen. 440 steel (usually 440C) is much more rust-resistant and easier to sharpen, but it goes dull faster.
420 Stainless Steel:
Offers good corrosion resistance in mild environments but is less resistant than 440 due to its lower chromium and carbon content. It is adequate for applications where occasional moisture or humidity exposure is expected.
D2 is moderately difficult to sharpen. It is a tough, wear-resistant tool steel with large, hard carbides, meaning it holds an edge incredibly well but takes longer to abrade than softer steels.
Balanced Hardness and Edge Retention
When properly heat treated, 420HC consistently reaches 56–58 HRC (Rockwell hardness). This range represents a sweet spot: hard enough to hold an edge for daily tasks, yet soft enough to avoid brittleness.
There is no single "best" steel for knives because the ideal choice depends on your primary need: edge retention, corrosion resistance, or toughness. Today, a few exceptional steels stand out as the top performers in different categories:
Experience knifemakers know that 440C steel cannot be used in an open-air forge successfully. In addition, knifemakers who don't heat treat their blades themselves will have difficulty working the 440C steel. The material must be het treated in a purified, restricted atmosphere to preserve its alloy content.
Navy SEALs rely on a few specific standard-issue fixed blades, but they largely carry mission-dependent gear. Standard-issue knives include the Ontario MK3 Mod 0 dive knife and the Cold Steel SRK. For everyday carry and field operations, operators frequently choose rugged folding knives from premium brands.
Recognized for its outstanding combination of extreme wear resistance, top-tier corrosion resistance, and exceptional edge retention, M390 is the gold standard for high-end knives and limited edition blades.
No, D2 steel does not rust easily, but it is not completely rust-proof. Often classified as a "semi-stainless" steel, it has high chromium content (around 12%) which gives it moderate-to-high corrosion resistance. It holds up well under normal use but requires basic maintenance.
Steel that does not rust is called stainless steel. It doesn't rust because it contains at least 11% chromium. When exposed to oxygen, the chromium forms an invisible, self-healing shield of chromium oxide that prevents the underlying iron from oxidizing and rusting.
Whether D2 is better than Damascus depends entirely on your priorities. D2 is a high-performance tool steel focused on raw cutting power and edge retention, while Damascus is a visually striking pattern-welded material whose performance depends on the specific steels used to create it.
AISI 4340 alloy steel can achieve a maximum surface hardness of approximately 60 to 65 HRC (Rockwell C) when subjected to specific case-hardening treatments like nitriding. Through-hardening and tempering typically yield a maximum core hardness of about 53 to 58 HRC.
In the high-end folding knife community, the original "Holy Trinity" refers to three legendary American makers who pioneered the modern premium tactical folder. Together, their designs set the gold standard for durability and precision.
Neither steel is objectively "better" overall; they simply excel at different things. The choice depends on your priorities: German steel is better for heavy-duty durability and low maintenance, while Japanese steel is better for razor-sharp precision and edge retention.
420HC is a stainless steel that provides excellent rust resistance, ease of re-sharpening and medium edge retention.
For production and custom knives, Rex 121, CPM-15V, Maxamet, and K390 hold an edge the longest. These are highly specialized, powder-metallurgy tool steels packed with extreme amounts of vanadium and tungsten carbides, which resist abrasive wear far better than standard blade steels.
(1) Ultra-high carbon crucible steel: We can ignore the pattern if we're considering the mechanical properties. High-carbon bloomery steel has some advantages over it, and could be called "better". It's easier to reliably heat treat with old technology, and could be used to produce tough blades with higher hardness.
Yes, you can use WD-40 as a lubricant on oil-based sharpening stones, but it is not the best option. Because WD-40 is very thin, it fails to effectively float away metal shavings (swarf), which can clog your stone.
Because D2 steel is highly wear-resistant with large carbides, diamond or high-quality ceramic abrasives are essential for efficient sharpening. Guided systems yield the best results for maintaining a precise, factory-style edge.
The main disadvantages of D2 steel include low toughness, susceptibility to chipping, difficult machining, poor high-temperature performance, and limited corrosion resistance.