Dozens of types of steel are used to create knife blades. Which one is right for you? We look at ten common steels used by popular knife brands to help you select the right material for your blade.
Steel is really the essence of the blade and primarily responsible for how the knife performs. Steel is essentially an alloy (i.e. a mix) of carbon and iron that is often enriched with other elements to improve certain characteristics depending on the desired application.
In the knife industry different types of steel are created by varying the types of additive elements as well as how the blade is rolled and heated (i.e. the finishing process).
Ultimately, the different types of steel used in knife blades each exhibit varying degrees of these five key properties:
Hardness is the ability to resist deforming when subject to stress and applied forces. Hardness in knife steels is often referred to as strength and is generally measured using the Rockwell C scale (aka “HRC”).
Toughness is the ability to resist damage like cracks or chips when being used in heavy duty applications. This also defines the steel’s ability to flex without breaking. Chipping is a knife’s worst enemy and never easy to fix. Note that the stronger or harder the steel the less tough it will likely be. Also, the measurement of toughness is less standardized as hardness.
Wear resistance is the steel’s ability to withstand damage from both abrasive and adhesive wear. Abrasive wear comes from softer surfaces coming in contact with rougher ones. Adhesive wear occurs when debris is dislodged from one surface and attaches to the other. Wear resistance generally correlates with the steel’s hardness but is also heavily influenced by the specific chemistry of the steel. In steels of equal hardness, the steel with larger carbides (think microscopic, hard, wear resistant particles) will typically resist wear better.
Corrosion resistance is the ability to resist corrosion such as rust caused by external elements like humidity, moisture and salt. Note that a high resistance to corrosion does involve a sacrifice in the overall edge performance.
Edge Retention represents how long the blade will retain its sharpness when subject to periods of use. It’s what everyone talks about these days but unfortunately the measurement of edge retention lacks any defined set of standards and so much of the data is subjective. For me, edge retention is a combination of wear resistance and an edge that resists deformation.
What are CPM steels?
CPM stands for Crucible Particle Metallurgy which is a process for manufacturing high quality tool steels. American Crucible Industries is the sole producer of CPM steels which are formed by pouring the molten metal through a small nozzle where high pressure gas bursts the liquid stream into a spray of tiny droplets. These droplets are cooled, solidified into a powder form and then hot isostatically pressed (HIP) where the powder is bonded and compacted. The trick here is that the HIP process ensures each of the fine particles have a uniform composition without any alloy segregation. All this results in a steel that has improved toughness, wear resistance and can be ground and heat treated with maximum effect.
Austenitic vs Martensitic Steel
Austenitic steel contains high amounts of nickel (around 8%) which makes it non-magnetic and relatively soft making it generally undesirable for knife making. However, the benefits of Austenitic steel are its toughness and superior corrosion resistance from high levels of chromium making it perfect for everyday items like forks, spoons, kitchen sinks, etc. Martensitic steel contains less chromium while still meeting the criteria for stainless steel but very little nickel thus making the steel magnetic. What really sets martensitic steels apart is higher levels of carbon which allows for the formation of Martensite, an extremely hard structure making it ideal for knifemaking. Steel manufacturers can transform austenite into martensite through rapid quenching.
What about Damascus steel?
Damascus steel originates from the middle east from countries like India and Pakistan where it was first used back in good old “BC” times. It’s instantly recognizable as it bears a swirling pattern caused by the welding of two different steels and so often referred to as “pattern-welded” steel (not to be confused with Wootz steel which is only similar in appearance). There are many myths about the strength and capabilities of Damascus steel but today it is largely popular because of its aesthetic beauty. Mostly for collectors only.
Remember, blade steel is not everything. Knife buyers should beware getting caught up in researching the perfect steel type as it is not by itself the only thing that dictates how a knife will perform. Steel analysis has become somewhat scientific that it’s easy to get caught up in the maze of statistics. Note – just because a blade is made from the premium or high-end steels listed above does not automatically mean it’s “better” than the lesser steels. The heat treatment techniques used by the manufacturer as well as the design of the blade itself play a huge role in the ultimate outcome of knife performance!
In reality, all modern steels will perform well enough for most users so consider spending more time on other aspects of the pocket knife such as how the knife handles and other features.