What is CPM Rex 45 Steel?
CPM Rex 45 steel is high-speed steel with 8% Cobalt in its composition. It is popular steel in Europe and japan produced by Crucible, following the powder Metallurgy process. Rex 45 has the same chemical composition as M3-2 but with Cobalt.
Cobalt boosts the hardness of CPM Rex 45 even at red heat temperature treatments. Because of the high hardness, this steel offers great wear resistance and edge retention capabilities.
CPM Rex45 is excellent in making cutting tools, knife blades, and cold working tools. Depending on the usage, some parts made of Rex 45 steel are passed through other treatments like nitriding to boost its qualities.
For nitriding, for instance, they diffuse Nitrogen and carbon on the metal, resulting in better corrosion resistance and strength.
CPM Rex 45 Steel Composition
- Carbon C 1.30%: Increases the edge retention, hardness and tensile strength. It also improves steel resistance to wear, abrasion and corrosion.
- Chromium Cr 4.05%: Formation of Chromium carbides Increases hardness, tensile strength and toughness of the blade.
- Molybdenum Mo 5.00%: It improves machinability and hardness.
- Vanadium V 3.05%: Increase wear resistance and toughness, it also improves corrosion resistance. High vanadium content enables formation of Vanadium Carbides.
- Cobalt Co 8.00%: Improves hardness of the blade as it increases the martensitic transformation temperature of the alloy, It also increases corrosion resistance of steel
- Tungsten W 6.25% Improves wear resistance and hardness, mostly added to tool steel
- Sulfur S 0.06%: helps improve machinability and grindability.
Properties of Rex 45 steel
CPM Rex 45 Steel Hardness
The hardness of Rex 45 steel depends on the heat treatment used, but it can attain a maximum Rockwell hardness of 67 HRC as per the Rockwell hardness scale. This high hardness level is attributed to the 8% cobalt in its composition.
Rex 45 Steel Toughness
Toughness measures the ability of steel to resist breakage, cracking, and chipping under stress and impact. If steel is not tough, it is brittle. In the world of steel, the toughness of steel reduces with hardness.
Being very hard steel, CPM Rex 45 is expected to perform poorly in toughness. However, it offers decent toughness. Steel types that offer a good balance in hardness and toughness make high-quality knife blades.
Rex 45 toughness is improved by the lack of a high amount of chromium carbide which tends to be prone to brittleness. Therefore, if you search for knives to be used in tough applications, the varieties of REX 45 will not disappoint you.
Rex 45 Steel Wear resistance
Because of the high hardness level, REX 45 offers excellent wear resistance. Therefore, knives made with CPM REX 45 will serve you for a long time because they do not wear out quickly from daily usage and sharpening.
Rex 45 Steel Edge retention
Another area of excellence of REX 45 is edge retention. Blades made of REX 45 steel offer superior edge retention. You do not have to sharpen the knife after every use, which saves you a lot of time and energy. Rex 45 edge retention is slightly better than that of M4 and the only thing that can distinguish them over each other is hardness level.
A more hardened Rex 45 steel will outperform virtually every steel out there with a lower hardness in edge retention only competing with the likes of Maxamet steel blades. Therefore, if you are in search of a knife that will hold its edges for a long time, REX 45 knives will not disappoint you.
Rex 45 Steel Corrosion Resistance
REX 45 steel is not stainless steel hence does not perform well in corrosion resistance. The amount of chromium in its composition does not reach the cut points to make it stainless steel; hence it requires extra care and maintenance to prevent corrosion.
If you are specifically searching for knives to use in highly corrosive environments, REX 45 knives are not suitable for you. However, if the knives serve your needs because of great hardness and exceptional wear resistance, go ahead with your purchase.
But ensure proper maintenance that involves washing and drying the knives after use to keep rust and stains away.
Rex 45 steel knives are known to easily develop a patina, some knife users also prefer to force patina their Rex 45 blades to avoid rusting in the long run. The patina on most Rex 45 steel looks amazingly beautiful but this boils down to personal preference.
Sharpening Rex 45 Steel
REX 45 is hard steel, so we expect it to be very hard to sharpen. However, REX 45 is easy to sharpen compared to other high-end steels. With the right sharpening tools and skills, you will get a sharp edge faster.
REX 45 steel comparison
CPM REX 45 vs. CPM M4
Rex 45 steel has a bit low Carbide volume content compared to M4 steel, this is due to the increased amount of vanadium element in CPM M4 alloy. Rex 45 offers better toughness and wear resistance than M4. REX 45 shines in hardness, edge retention and it is easier to sharpen.
Both steels are not stainless steels hence require proper care and maintenance to prevent rusting.
CPM REX 45 vs. M2
REX 45 is better steel than M2 in all aspects. It offers better hardness, toughness, wear resistance, edge retention, and ease of sharpness. They both offer poor corrosion resistance and would not make a good pick for a knife to be used in a corrosive environment.
CPM Rex 45 vs M390
M390 steel has about three times the carbide volume of Rex 45 steel and it is stainless. It is a better corrosion resistance steel than Rex 45 steel. In terms of edge retention, Rex 45 may outperform M390 steel even though M390 has a high amount of carbides.
This is because M390 has a lot more chromium in its alloy which tends to form more chromium carbides than vanadium carbides. Vanadium carbides are the best when it comes to edge retention and hardness, so ideally you should be looking for knife steel with high vanadium carbide volume.
CPM Rex 45 vs K390
Rex 45 steel has a higher Rockwell hardness level than k390 steel. Their performance is in the same ball pack. Edge retention on both steel is excellent and the only difference will result in how hardened each is. Rex 45 steel slightly wins in edge sharpness but not by any significant margin.
They both offer an almost similar level of toughness, you will get great performance with either of the two. They also aren’t corrosion resistant as stainless steel since they contain a low amount of chromium in their alloys.
CPM Rex 45 vs Maxamet
While CPM Rex 45 is incredibly hard at a Rockwell hardness of 67 HRC, Maxamet steel by Spyderco outperforms it at an impressive hardness of 70 HRC due to the high amount of Vanadium. Spyderco Maxamet beats CPM Rex 45 steel in edge retention, toughness, and wear resistance owing to the fine microstructure of its vanadium carbides.
Both steels will however need extra care to avoid rusting as they do not qualify as stainless steel. Rex 45 steel is also a bit easier to sharpen than Maxamet Steel.
Is REX 45 good knife steel?
CPM REX 45 is good knife steel because it offers excellent hardness, edge retention, and wear resistance for high-end performance. The addition of cobalt and tungsten in its alloy ensures that Rex 45 steel knives are extremely hard and incredibly resistant to wear.
Very few steels can match the hardness of Rex 45 steel, Maxamet steel from Spyderco is one of them.
However, it is not stainless steel hence cannot be used in highly corrosive environments. This is the only downside of Rex 45 steel. With care and maintenance, it is great knife steel.
Check out Spyderco Para 3 Rex 45 steel knife
My name is Jonathan M, and I’m a passionate Mechanical Engineer, a knife enthusiast, and the author of this website. I have a bachelor's degree in Mechanical engineering with a specialization in material science. I am particularly interested in researching knife steel, knife properties, and brands. I hope you will find value in the articles on this website. Contact me if you have any questions or input!