Significant attention is given to the type of steel used in the blades when choosing a knife for a particular application. Blades become blunt upon frequent usage due to wearing and thus improving its characteristics have become an important prospect in various firms. Steel is an alloy of iron and carbon with other materials present in a small amount to improve its properties. The common attributes are compared when describing the characteristics of knives these includes; (1) Edge retention, which indicates the ability of a blade to retain its sharpness when consistently used. (2) Corrosion resistance, which takes the form of rust and staining damaging the structural integrity of the knife blade. (3) Ease of sharpening, which refers to the difficulty in removal of material by a sharpening stone. (4) Wear resistance, which indicates steels ability to endure damage from adhesive and abrasive wear and (5) Toughness, which alludes to the steels ability to resist cracking when subjected to impact loads.
Limited studies have tested and evaluated steel knives based on the properties mentioned earlier. (Marsot, Claudon and Jacqmin, 2007) developed a knife evaluation method (KSM) based on this technique and established that 40 N force as a criterion to determine if the knife needs sharpening. Researchers (McCarthy, Annaidh and Gilchrist, 2010; Schuldt et al., 2016) have also regarded blade geometry as a crucial factor in determining the blade’s cutting performance. (Verhoeven, Pendray and Clark, 2008) studies the effects of two different edge blades on the knife performance and also indicated that martensitic stainless steels perform better than high carbon steels. Sharpness is considered to be the determining attribute as greater sharpness will require less force to cut an object. Knife’s sharpness capability is enhanced upon addition of other materials like carbon especially in its martensitic phase (Zhu et al., 2017). The dimensionless parameter BSI (Blade sharpness index) was developed by (McCarthy, Hussey and Gilchrist, 2007) relating the energy compulsory to initiate a cut to the product of cut initiation depth, fracture toughness and thickness of the object material.
The preventing corrosion, steels are often alloyed with materials like Chromium or Manganese that form a passive layer (Olsson and Landolt, 2003) on the knife surface. Martensitic stainless steels (MSS) are consistently used in knife making because they yield good corrosion resistance and edge retention. Steels of other different types are also commonly used in making knives, these include;
- Carbon steel: They are developed by mixing carbon and iron and are well-known for their ease of sharpening, durability and edge retention, although it is susceptible to corrosion.
- Stainless steel: This type of steel contains chromium which renders it resistant to corroding however, they are not easy to sharpen and are weaker than carbon steel knives.
- Damascus steel: It is a combination of two or more steels layered and forged together. They possess high edge retention and sharpness but are difficult to sharpen.
- Tool steel: Tool steel is highly heat resistant and hard due to the presence of durable elements like vanadium, tungsten, cobalt and molybdenum.
Dr. Larrin Thomas, a professional metallurgist developed an online source pertaining to knowledge of knife steels (Knife Steel Nerds, 2023). Over 40 blades have been forged by them using the popular alloys keeping the same angle (30° inclusive and 15° per side) recorded their Rockwell Hardness ratings after tempering and quenching and put them through standardized cutting tests. Each blade was used to cut through the cardstock stack with equal force applied and was forced to cut until its edges cut not cut any longer. The results are indicated in figure 1 left.
(Noblie, 2022) and (BladeHQ, 2022) own a vast collection of knifes and they have studied the properties of steel blades and ranked them based on their performance. The list contains low-end, low mid-range, high mid-range, high-end, premium and ultra-premium steels based on their performance characteristics. In terms of corrosion resistance, the H1 steel is a great performer while CPM S110V has the best edge retention. The ZPD-189 blade shows the highest hardness number in Rockwell test compared to the other materials whereas 1095 steel leads the list in terms of ease of sharpening.
|PROPERTY||BEST STEEL TYPE|
|Edge Retention||CPM S110V is considered to have the best edge retention among the steels compared in this study. This steel is known to retain its edge longer than other steels, making it ideal for heavy-duty tasks such as chopping and slicing. VG-10 also performs well in edge retention and is considered a close second to S30V. CPM S35VN, CPM 154, AUS-8 and 440C are also known to have good edge retention but not as good as S30V and VG-10|
|Sharpness||VG-10 is considered to have the best sharpness among the steels compared in this study. This steel is known for its excellent edge retention and sharpness, making it ideal for precision tasks such as slicing and peeling. CPM S30V, CPM S35VN, CPM 154, AUS-8 and 440C are also known to have good sharpness but not as good as VG-10.|
|Corrosion Resistance||H1 steel is considered to have the best corrosion resistance among the steels compared in this study. It is highly resistant to rust and corrosion, making it ideal for use in damp or humid environments. CTS BD1N is the second best performer while VG-10, CPM 154, AUS-8 and 440C are also known to have good corrosion resistance but not as good as H1 and CTS BD1N.|
|Toughness||AEB-L steel is considered to have the best toughness among the steels compared in this study. The addition of niobium in this steel improves its toughness, making it more resistant to chipping and breaking It is made by Bohler Uddeholm in Sweden. CPM 3V, VG-10, CPM 154, AUS-8 and 440C are also known to have good toughness but not as good as S35VN.|
|Ease Of Sharpening||CPM 154 is considered to have the best ease of sharpening among the steels compared in this study. This steel is known for its good balance of edge retention and corrosion resistance, and it is relatively easy to sharpen. AUS-8 is also considered to be easy to sharpen. CPM S30V, VG-10, CPM S35VN and 440C are also known to be easy to sharpen but not as easy as CPM 154 and AUS-8.|
However, the knife being better in one characteristic ends up performing inferior in other characteristics and thus a trade-off must be made during selection process. There is no best knife that excels in all properties however, among the steel grades discussed, there are some that will prove to be an excellent option under various circumstances. The top 5 of them are discussed below;
CPM S110V is a high alloy martensitic stainless steel and is developed by Crucible Particle Metallurgy (CPM) process (ASM, 2022). It contains high amount of Niobium and Vanadium. Additionally, it is considered as a premium steel and may be relatively expensive compared to other steels in the market. It is an enhanced version of CPM S100 and is used in slitters, parts of screws and bolts, cutters and also medical industry. It has exceptionally high degree of edge retention and is able to cut abundant amount of objects. It also has good corrosion resistance but is difficult to sharpen and can also chip away in case of forceful usage.
CTS-XHP (also known as Carpenter CTS XHP) is a high-performance stainless steel that is known for its exceptional edge retention, toughness and corrosion resistance. It is a powder metallurgy steel, which means that it is made using a process that allows for more uniform distribution of carbides, which can result in improved properties (ASM, 2010). It is considered to be one of the hardest steels available, making it ideal for heavy-duty tasks such as chopping and slicing. Additionally, it is relatively easy to sharpen, making it a good option for those who are not experienced in sharpening knives. CTS-XHP is also relatively affordable compared to other premium steels. However, it is considered to be a newer steel and may not be as readily available as some of the more established steels in the market.
CPM S35VN is a martensitic steel designed to impart better toughness to S30V grade. It also has high corrosion resistance along with good ease of sharpening but moderate edge retention. It has a fine grain structure with meager quantity of niobium added to enhance its properties. It is developed by Crucible Industries CPM process yielding a homogenous high quality steel as compared to those produced by conventional melting practices.
154 CM is an excellent budget to mid-range choice. It is a hard steel with a fine edge holding and despite having less chromium shows great resistance to corrosion. It was introduced as a proprietary American-made high-carbon stainless steel melted in a vacuum and was developed as an upgrade over traditional 440C steel. It is easy to sharpen and utilized in many pocket knives and is also a great choice for hunting knives.
D2 steel is often referred as semi-stainless as it lacks the amount of chromium required to qualify as stainless steel. It not only excels in corrosion resistance but holds a sharp edge and is made by Carpenter technology in USA. However, it is considered to be one of the more difficult steels to work with, as it requires a high level of skill to properly heat treat and finish. It is also considered to be a bit more brittle compared to other premium steels like CPM S35VN or CTS-XHP, and it is relatively expensive compared to other steels in the market, making it a good option for those who are looking for a high-performance steel and are willing to pay more for it.
ASM, 2010. CARPENTER CTS-XHP ALLOY: Martensitic Stainless Die Steel. Alloy Digest, 59(3), p.SS-1057. https://doi.org/10.31399/asm.ad.ss1057.
ASM, 2022. CRUCIBLE CPM S110V: Powder Metallurgy High-Alloy Tool Steel. Alloy Digest, 71(8), p.TS-830. https://doi.org/10.31399/asm.ad.ts0830.
BladeHQ, 2022. Knife Steel Guide. Knife Life. Available at: <https://www.bladehq.com/blog/knife-steel-guide/> [Accessed 27 January 2023].
Knife Steel Nerds, 2023. Knife Steel Nerds – Metallurgy and Testing of Knives and Steel. [online] Knife Steel Nerds. Available at: <https://knifesteelnerds.com/> [Accessed 27 January 2023].
Marsot, J., Claudon, L. and Jacqmin, M., 2007. Assessment of knife sharpness by means of a cutting force measuring system. Applied ergonomics, 38(1), pp.83–89.
McCarthy, C.T., Annaidh, A.N. and Gilchrist, M.D., 2010. On the sharpness of straight edge blades in cutting soft solids: Part II–Analysis of blade geometry. Engineering Fracture Mechanics, 77(3), pp.437–451.
McCarthy, C.T., Hussey, M. and Gilchrist, M.D., 2007. On the sharpness of straight edge blades in cutting soft solids: Part I – indentation experiments. Engineering Fracture Mechanics, 74(14), pp.2205–2224. https://doi.org/10.1016/j.engfracmech.2006.10.015.
Noblie, 2022. Choosing the best knife steel. [online] Noblie. Available at: <https://noblie.eu/choosing-the-best-knife-steel/> [Accessed 27 January 2023].
Olander, T., 2022. Which Knife Steels Have The Best Edge Retention? Knife Know-It-All. Available at: <https://knifeknowitall.com/which-knife-steels-have-the-best-edge-retention/> [Accessed 27 January 2023].
Olsson, C.-O. and Landolt, D., 2003. Passive films on stainless steels—chemistry, structure and growth. Electrochimica acta, 48(9), pp.1093–1104.
Schuldt, S., Arnold, G., Kowalewski, J., Schneider, Y. and Rohm, H., 2016. Analysis of the sharpness of blades for food cutting. Journal of Food Engineering, 188, pp.13–20.
Verhoeven, J., Pendray, A. and Clark, H., 2008. Wear tests of steel knife blades. Wear, 265, pp.1093–1099. https://doi.org/10.1016/j.wear.2008.02.021.
Zhu, Q., Li, J., Shi, C., Yu, W., Shi, C. and Li, J., 2017. Precipitation behavior of carbides in high-carbon martensitic stainless steel. International Journal of Materials Research, 108(1), pp.20–28.