We break down what common steel alloying elements add to a knife.

Alloy… in the knife world we hear the word often. Blade aficionados—many almost journeyman metallurgists in their own rights—pour over steel composition. Newbies to collecting and making, however, might be a bit perplexed over exactly what the material modification is all about.

With this in mind, we’ve boiled down what certain elements—when alloyed with iron—bring to the table for your knife. Now this isn’t a deep dive into the nitty-gritty of what each element does in a steel alloy, complete with phase diagrams and quenching charts. Honestly, if you need to cut to this quick, we recommend Larrin Thomas’ website KnifeSteelNerd.com. The son of BLADE Cutlery Hall of Fame member Devin Thomas and PhD metallurgist and material scientist, Thomas offers a much more in-depth look at steel from an engineer and knifemaker’s point of view.

What we have here is a quick and dirty guide to alloy elements and what they bring to a knife.

What An Alloy Is

If your high school chemistry class is a bit foggy right now, perhaps we should take a moment to do a quick review of exactly what constitutes an alloy. Quite simply, an alloy is a mixture of two or more elements, where at least one of the elements is a metal. Note alloys are mixtures, not compounds—the former is a physical combination, the latter a chemical. For a mixture, think of something like oil emulsified in vinegar to create a tasty salad topping, while a compound is two gases like hydrogen and water bonding together to form water.

Alloying elements is done to enhance the properties of a material. In the case of knife steel elements are combined to improve toughness, wear resistance, corrosion resistance or other factors. While we won’t delve that deep in this article, we’ll point alloys can be classified into two main types:

Substitutional Alloys: In these alloys, the atoms of one element replace or substitute for the atoms of another in the metal lattice. An example is brass, which is an alloy of copper and zinc.

Interstitial Alloys: In these alloys, smaller atoms fit into the spaces (interstices) between the larger metal atoms in the lattice. Steel, which is an alloy of iron and carbon, is an example of an interstitial alloy.

Since we’ve dusted off some of those long-lost materials lessons you learned, let’s get into the down-and-dirty of what each common alloying element brings to knife steel.

Knife Steel Alloy Elements

Carbon: This ingredient makes the difference between iron and steel; all steel will have some amount of carbon. It is the most important hardening element, but it makes hardness by combining with other elements. As a simple generalization, the amount of carbon in the steel tells you a lot about the quality of the steel. Low-carbon steel has 0.3% carbon or less, medium has between 0.4-0.7% and high-carbon steel is 0.8% and above, maxing out at around 1.2% carbon for knife steels. Up to a point, the higher the carbon content within the range, the harder the steel will get.

Chromium: Chromium combines with carbon to make chromium carbides, which are resistant to corrosion. Stainless steel knives will have chromium as a major ingredient, typically at a minimum of 12-13%. Chromium also increases the strength of a knife to a degree, but adding chromium in large amounts decreases toughness.

Cobalt: In small amounts, cobalt increases toughness.

Manganese: This changes the rate of hardening. Manganese in carbon steels yields “deeper” hardening, which requires a slower speed quench and gives a wider range of acceptable heat before quench. If added in high quantities, it can increase brittleness. Manganese makes steel etch dark in damascus.

Molybdenum: Adding this maintains the steel’s strength at high temperatures.

Nickel: Nickel adds toughness to steel. It also makes steel etch bright in damascus.

Nitrogen: This element is sometimes used as a substitute for carbon in steel.

Silicon: Silicon increases strength and removes oxygen from the metal while it is being formed. It’s typically present in small quantities in most steels.

Sulfur: This increases machinability but decreases toughness.

Tungsten: Adding this increases wear resistance and forms tungsten carbides that are very hard.

Vanadium: Vanadium leads to smaller grains within the steel. Vanadium carbides are very small and hard, which increases wear resistance and edge retention.

More On Knife Steel:

• Damascus Steel
• Knife Steel Type Performance
• Knife Steel Basics
• Steel for Forging