SUMMARY: CPM 345VN steel is a high alloy stainless steel with outstanding edge retention, increased corrosion resistance, and modest toughness. These properties make S45VN is outstanding blade steel for high-end folding knives. It is a step forward from S35VN but its improvements are incremental better not orders of magnitude better. There are three significant things to know about S45VN steel: it has high vanadium content for very tough carbides (edge retention), it has high chromium for increased corrosion resistance, and niobium content for a cleaner grind/machinability.
In late 2019, Crucible industries in collaboration with Niagra Speciality Metals debuted CPM S45VN. S45VN is specifically designed to enhance their S30V and S35VN series for general high-end cutlery and cutting tools.
CPM = Cruidible Powder Metallurgy
Powder steel is a technology that was invented to allow the production of high alloy tool steels. In 1970, Crucible Industries pioneered in the production of powder metallurgy tool steels. The company has been producing steel with high wear resistance, corrosion resistance, and toughness by adding vanadium and niobium when creating new products. S60V was the first CPM steel produced by the company through the modification of common stainless grade 440C steel by increasing the composition of vanadium with a corresponding increase of carbon elements.
CPM technology was used in the manufacture of homogeneous steel through the even distribution of carbides in the blade. Carbides refer to the hard particles present in steel that enhance the blade to retain its edge. The need to develop tough martensitic stainless steel saw the introduction of CPM S30V steel, which Chris Reeves was directly involved in creating. The steel was designed to offer good wear and corrosion resistance as well as increased toughness in knives. S30V quickly became a favorite for knife manufacturers in the 2000s. However, its corrosion resistance was not the very best hence the advancement to S35VN.
CPM vs Conventionally Produced Steel (Source Crucible Industries Datasheet)
Crucible Industries has been producing steel with high wear resistance, corrosion resistance, and toughness by adding vanadium and niobium when creating new products. S60V was the first CPM steel produced by the company through the modification of common stainless grade 440C steel by increasing the composition of vanadium with a corresponding increase of carbon elements.
Knifemaker Jeff Freeman of Freeman Outdoor Gear mentioned that, "I think CPM S45VN is a good improvement, both for the maker and the end-user. It's about the same edge retention as S30V but with better toughness and corrosion resistance. It's similar in toughness to S35VN but you get improved corrosion resistance and edge retention. For the maker, it appears to result in longer tool life and possibly increased speeds and feeds with the accompanying decrease in cycle time and machine time. Overall, I'm pleased with it, and more importantly, my customers are satisfied."
A further modification was made with the S35VN, niobium increased carbides that contribute to the refinement of the grain size and increase wear resistance. The effected change led to the formation of a finer carbide structure, with improved toughness, and machinability. With this in mind, the chemical composition used in the manufacture of S35VN was rebalanced with the addition of chromium for an improvement in corrosion resistance coming up with a new product: S45VN.
CPM S45VN Alloy Composition (Source Crucible Industries Datasheet)
Composition of S45VN
As the latest evolution of alloy steel, S45NV has increased amounts of chromium to help increase corrosion resistance over the earlier generation of S35VN. Its composition has been altered to create more chromium carbides, while also allowing free chromium compounds in the composition. While earlier generations of steel relied on Vanadium, replacing this element with niobium created harder particles that contribute to the wear resistance of steel.
The replacement of vanadium and carbon with niobium and nitrogen produces an excellent combination of wear and corrosion resistance, edge retention, and toughness making this the ideal choice in the manufacture of knives. The more the carbides present the tougher and brittle the steel. A low combination of very hard carbides can give a better balance of properties compared to a larger volume of softer carbides. Vanadium carbides are classified as the hardest carbides, hence the incorporation of V in the name of the metals. Niobium carbides are also hard hence used in place of vanadium to form higher wear resistance. The CPM process used enhances the production standardized, high-quality steel with superior dimensional solidity, toughness, and machinability.
Comparison Between S45VN and S35VN
Functional Comparison of S45VN vs other Knife Steels (Source Crucible Industries Datasheet)
S35VN, which was introduced in 2009 uses the modified formula of S30V, which is made with 1.45% carbon, 4% vanadium, and 10.5% chromium carbide with the addition of niobium to the vanadium and chromium carbide forming elements. The addition of niobium is reflected with the addition of N in the name which is absent in the S30V. S35VN, which is the mainstream steel, contains lower components of niobium and lacks nitrogen, which is added to S45VN to increase toughness. S45VN uses a similar chemical formula but with a rebalance of the percentage compositions of the elements. Nitrogen was added in place of carbon and niobium increased in place of vanadium to improve corrosion resistance present in S35NV.
While corrosion resistance is important a knife's key role is cutting hence holding its edges is a vital feature. With increased carbon content and less vanadium, S45VN holds an edge longer as compared to its predecessors. This difference can be felt when whittling and cutting fibrous materials like cardboard and ropes despite the lack of change in heat treatment, the S45VN has a hardness rating of 61-62 compared to 59-60 of the S35VN. This also means that there will be longer periods between sharpening time. Knifemaker Jeff Freeman of Freeman Outdoor Gear remarked, “Edge retention appears to be very similar or maybe just slightly better than S30V and S35VN. Possibly due to a 2,000F AUS temperature that gives a higher hardness, among other things."
As seen in the formula composition, S45VN has a higher chromium content as compared to the S35VN. The higher content means an increase in corrosion resistance. From an experiment where the two steels were subjected to heat 1950 °F, the results after 24 and 48 hours respectively showed that S45VN was better to withstand corrosion resistance as compared to S35VN. Freeman also said that “I think the main advantage of S45VN is the increased corrosion resistance. I've seen it in processing and in the finished product."
Why Choose S45VN for knifemaking?
In its annealed condition, CPM S45VN is a lot easier to grind than CPM S90V and simpler than CPM S30V. The addition of hard carbides to the steel makes it the best option among manufacturers of stainless steel knives. While various manufacturers have already put out the S45VN knife in the markets, it is bound to be more resistant to corrosion and wear as well have tough on edge retention. Although S35V seems to be better on toughness, this toughness can be incorporated in S45VN through heat treatment at 2000 °F. Further fast-quench and cold treatment are recommended at 400°F temperatures depending on the desired levels of hardness.
A Knifemakers Perspective S45VN
Selecting a steel to use in a knife is a balance between the intended use (features required), the cost of the steel (price point), and the difficulty both to cut, grind and heat treat the steel. Steels have varying levels of difficulty working the steel, can require specialized tools and exacting heat treatment.
S45VN fits the bill for high-end knifemakers that require excellent edge retention and corrosion resistance that is relatively easy to work. Custom knifemaker Jeff Freeman mentioned, that machining and cutting S45VN steel for blades, "For processing, I use the same tools (solid carbide) with the same coolant and fixturing. And the exact same programming. But it does appear that I'm getting a little bit better life out of my cutting tools. Time will tell for sure, as I have not made more than a couple of hundred blades, but things are trending that way. On future batches, I will try and up the speeds and feeds and possibly depths of cut to see if I can decrease cycle times and maintain cutting tool life and dimensional precision/repeatability."
"For edge toughness, I haven't been able to discern any difference but that is likely more due to my edge geometry and processes. I run the pre-sharpened edge thickness a bit higher than most at around .040". Add in the machined "grooves" on the bevels, and the edge thickness can be .050" prior to sharpening. And of course, this varies along the edge from machined peak to valley. I didn't really plan it that way, but it works out that this edge type, when combined with a relatively steep sharpening angle of 17 degrees per side gives a really tough sharpened edge. I think this is due to the supporting material behind the edge. Which makes it probably not the best "slicer" with .156" stock and a 5-degree bevel, but it sure makes a good and tough utility edge that maintains sharpness in use across a wide variety of cutting media.
S45VN steel seems to provide a good canvas to for surface finishes. Freeman mentioned, “Not a knock on any other CPM steels, but so far this seems "cleaner", meaning that it gives a very uniform surface appearance across a large surface area. This is in reference to surface grinding water jet cut blanks to final thickness. As for edge finishing, I have been going with a 100 grit, then a 220 grit, then a 400 grit at 17 degrees per side, then a buffing wheel with green chrome to finish. It gives a nice sharp bright and mirror-polished finish on the edge."
Uses of S45VN steel
The most common and tested used of S45VN steel in the manufacture of blade knives for hunting, diving, combat, and kitchen use. Other possible uses include the manufacture of industrial machinery include: pelletizing equipment, extrusion feed screws, non-return valve components, components for food and chemical processing.
Download the Crudible CPM S45VN Steel Datasheet