CPM REX T15 Steel

CPM REX T15 Steel Spyderco

In this article, we will delve into the properties of CPM REX T15 Steel and explore its composition, hardness, edge retention, wear resistance, corrosion resistance, and toughness.

Whether you’re a knife enthusiast or a professional looking for a durable and high-performance steel, this article will provide you with all the information you need to make an informed decision.

What is CPM Rex T15 Steel?

CPM Rex T15 is high-speed tungsten steel manufactured following the Crucible Particle Metallurgy (CPM) process. It contains high amounts of Vanadium and Carbon, which gives it excellent wear and abrasion resistance. The high Tungsten content greatly improves the red hardness of Rex T15 Steel.

CPM REX T15 steel is a high-speed steel that is specifically designed for high-temperature applications such as cutting tools and drills. It’s commonly used in the manufacturing of:

  • End mills for high-speed machining
  • Drills for drilling at high speeds
  • Taps for threading at high speeds
  • Reamers for accurate hole sizing and finishing
  • Broaches for internal shaping and cutting

CPM REX T15 steel is known for its excellent combination of high hardness, wear resistance, and toughness, making it ideal for use in demanding machining and drilling applications where high cutting speeds and temperatures are required.

Additionally, its composition and microstructure provide excellent resistance to heat and thermal fatigue, making it a preferred choice for high-temperature applications.

Because of its high quality and grind ability, CPM Rex T15 steel is designed to make tools for use in difficult operations that produce high frictional heat. Few knife makers have adopted Rex T15 steel like Spyderco in the Mule Team™ CPM Rex T15 Pocket knife

CPM REX T15 Steel Composition

  • Carbon C 1.60%: Increases the edge retention, hardness and tensile strength. It also improves steel resistance to wear, abrasion, and corrosion.
  • Chromium Cr 4.00%: The formation of Chromium carbide Increases the hardness, tensile strength and corrosion resistance of the blade.
  • Molybdenum Mo 1.30%: It improves machinability and hardness.
  • Vanadium V 4.90%: Increase wear resistance and toughness, it also improves corrosion resistance.
  • Manganese Mn 0.30%: improves the strength and hardness of steel. When the steel is heat-treated, hardenability is improved with increased manganese.
  • Tungsten W 12.00%: used as an alloying ingredient due to its high melting point, hence improving the performance of steel in high heat.
  • Cobalt Co 5.00%: Increases the strength of steel and hot hardness temperature.
  • Sulfur S 0.06%: Improves machinability but is regarded as an impurity in high quantities.

Properties of CPM REX T15 steel

Steel Hardness

CPM Rex T15 has a Rockwell hardness of 64HRC, but it can reach 67HRC depending on the heat treatment. This high hardness is associated with the blend of Carbon, Vanadium, cobalt, and tungsten in its composition. 

Tungstenimproves the red hardness of the steel at very high temperatures while Cobalt improves the strength of Steel. The high level of hardness of CPM Rex T15 shows that it is durable, abrasion resistant, and has high edge retention.

Steel Edge retention

Edge retention of steel is directly proportional to the level of hardness. With a high Rockwell hardness of 64HRC, CPM Rex T15 offers great edge retention. A CPM Rex T15 steel will stay sharp for a very long time with a rare need to sharpen. 

The varieties of REX T15 knives are suitable for situations that do not allow for frequent sharpening. The edge retention of Rex T15 steel is in the range of other steels like S60V steel and Vanadis 8 Steel, Rex T15 steel is better than CPM Rex 45 steel

Wear Resistance

Wear resistance is another area of excellence for CPM Rex T15 high-speed steel as it is a hard alloy. Even with everyday use, the wear and tear of Rex T15 blades are minimal. Adding cobalt and tungsten to its composition improves the wear resistance. 

With proper care, Rex T15 knives can last an entire generation. The wear resistance of Rex T15 Steel is better than the popular CPM M4 Steel but slightly lower than that of CPM 10V and CPM 15V steel.

Corrosion Resistance

The corrosion resistance of steel is mostly determined by the amount of chromium in its composition. Rex T15 steel does not perform well in corrosion resistance because it contains low amounts of chromium in its chemical composition. 

CPM Rex T15 steel is not stainless steel because it only has 4% chromium which does not meet the 12% chromium content requirements to make steel stainless. CPM Rex T15 steel knives are prone to rust and stains, especially in humid areas, but they can serve you for years if you take care of them. 

Proper care involves cleaning and drying the knives after every use, using a knife holder, and applying a coat of oil on the blades for storage.


The toughness of steel is mostly inversely proportional to the hardness. Steel with high hardness and great wear resistance is mostly brittle, but this is not the case with CPM Rex T15. Its toughness is higher than most steels, with a Rockwell hardness of 64 HRC. 

With its toughness level, CPM Rex T15 knives can be used for tough but not very challenging applications without chipping or breaking. Rex T15 knife steel toughness is slightly lower than that of CPM 10V steel but better than that of CPM 15V steel.

Ease of sharpening REX T15

With a Rockwell hardness of 64HRC, Rex T15 is very challenging to sharpen. Getting a sharp edge will take time and energy and require excellent knife sharpening skills. It helps to use sophisticated sharpening tools, which are harder than CPM Rex T15.

Machinability of REX T15 Steel

Machinability determines the ease of working with steel, and it depends on the chemical composition and hardness of the steel. Rex T15 is difficult to machine compared to steel with lower Rockwell hardness. On the other hand, it is easier to machine compared to other tungsten tool steels.

Compared to other high-speed steels, CPM Rex T15 has the following pros and cons:


  • High toughness: CPM Rex T15 has a high level of toughness, which means it can resist chipping and breaking even when subjected to high stress. This makes it ideal for knife blades that need to withstand heavy use.
  • Good wear resistance: The steel has excellent wear resistance, which helps to maintain the sharpness of the blade for longer periods.
  • Consistent performance: CPM Rex T15 has a consistent performance, even when subjected to high temperatures and stress, which helps to maintain its edge retention and toughness.


  • Cost: CPM Rex T15 is a premium high-speed steel and can be more expensive compared to other high-speed steels.
  • Complex heat-treating process: The steel requires a complex heat-treating process to achieve its desired properties, which can make it difficult for some manufacturers to work with.

Compared to other high-speed steels, CPM Rex T15 has a balance of high toughness and wear resistance, making it a versatile option for knife blades. However, its cost and the complexity of the heat-treating process can be drawbacks for some manufacturers.

CPM Rex T15 steel comparison

Rex T15 vs S30V

Rex T15 offers better edge retention and wear resistance than S30V because it has high hardness and the presence of hard vanadium carbides in its composition. S30V shines in corrosion resistance because it is stainless steel, while Rex T15 is not stainless steel.

Rex T15 vs M390

M390 offers better corrosion resistance than REX T15 because it is stainless steel, while Rex T15 is not stainless steel. On the other hand, Rex T15 has high hardness and therefore offers better edge retention and wear resistance than M390.

Care for CPM Rex T15 steel knives

To ensure the longevity and durability of CPM Rex T15 steel knives, proper care should be taken to maintain the blade’s qualities. Here are some tips:

  1. Clean and dry the knives after every use: This will help prevent rust and stains that can weaken the blade.
  2. Use a knife holder: Store the knife in a dry place to prevent moisture from accumulating on the blade and causing rust.
  3. Apply oil to the blades for storage: Oil helps to protect the blade from moisture and rust, preserving its longevity and durability.
  4. Avoid exposing the knife to harsh chemicals: Chemicals can corrode the blade and reduce its quality.
  5. Avoid using the knife for tasks outside of its capabilities: Overuse or misuse can damage the blade and reduce its longevity.

By following these tips, the CPM Rex T15 steel knife can serve you for many years and retain its high performance qualities.

Is CPM Rex T15 good knife steel?

CPM Rex T15 Steel is good knife steel because it offers high hardness, excellent wear resistance, outstanding edge retention, and decent toughness.

The major downside is that it is not stainless steel and is challenging to sharpen due to the excellent wear resistance. Machining Rex T15 steel is also difficult and requires experienced knife makers. 

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