CPM S125V Stainless Steel

CPM S125V is a high-chromium martensitic powder stainless steel developed by Crucible Industries. It is known for its exceptional hardness, wear resistance, and corrosion resistance, making it a popular choice for knives, tools, and other components that require high performance.

CPM S125V is not just stainless steel, it is the pinnacle of knife making. This product of the American company Crucible Industries combines incredible hardness, resistance to abrasion and corrosion, making it an impeccable choice for the most demanding users.

Unrivaled Hardness: thanks to its unique chemical composition and innovative powder technology, CPM S125V achieves a hardness of up to 65 HRC (according to some sources, up to 66 HRC). This makes it one of the hardest of its kind on the market, capable of withstanding extreme loads and maintaining its sharpness for a long time.

Incredible abrasion resistance: CPM S125V knives are not afraid of any test. Their blades hold an edge better than any other steel, thanks to the extremely resistant vanadium carbides in their structure. Cut, chop, mince - S125V copes with any task without losing its cutting properties.

Excellent corrosion resistance: CPM S125V does not rust. Due to its high chromium content, this steel is resistant to corrosion in many of the most aggressive environments. This makes it an ideal choice for knives used in high humidity conditions or in contact with aggressive substances.

CPM S125V - steel for the best: this steel is not for mass production. Its complexity and high cost make it available only to the best knife makers who strive to create true masterpieces. Knives with CPM S125V are not just tools, they are works of art that are passed down from generation to generation.

If you are looking for a knife that will never let you down, then CPM S125V is your choice. This steel will become a legend in your hands.

Chemical composition

CPM S125V is a high-alloy martensitic stainless steel produced by crucible metallurgy (CPM). CPM S125V contains a high volume fraction of vanadium carbides and chromium carbides, which provides high wear resistance and corrosion resistance.

The CPM process produces highly homogeneous, high quality steel characterized by superior dimensional stability, grindability and strength compared to steels produced by conventional steelmaking.

Physical properties

• Modulus of elasticity: 32 X 10⁶ psi (221 GPa)
• Density (specific gravity): 7.31 g/cm³ )

Heat treatment and hardness

All samples were austenitized in the molten state, quenched in oil, and tempered twice at the specified times and temperatures. The last column includes deep freezing after the first tempering.

Corrosion resistance

CPM S125V is a high-alloy martensitic stainless tool steel produced by Crucible Industries (USA). The alloy has a corrosion resistance comparable to ZDP-189 steel, i.e. its corrosion resistance is quite high. ZDP-189 steel contains 20% chromium versus 14% in CPM S125V. The amount of carbon is approximately the same. It would seem that CPM S125V should rust more, but ZDP-189 has much more chromium converted into carbides than S125V, where vanadium also goes into carbides. As a result, the chromium content in the solid solution for both steels is not that different.

History of CPM S125V stainless steel

The appearance of stainless steel grade S125V is inextricably linked with another stainless steel S90V. Taking CPM S90V as a basis, specialists from Crucible Industries wanted to obtain a similar alloy but with slightly better characteristics. But they had to sacrifice other useful properties. And almost immediately after the release of the S90V grade, experiments began to create an alloy with even greater hardness. Initially, the path was saturated with nitrogen, replacing carbon with this element (in the S90VN alloy, more vanadium carbides were obtained instead of chromium carbides). However, then the developers decided to go the opposite way. The nitrogen saturation was reduced, but the percentage of carbon was increased. But simply increasing the carbon content in the alloy did not help, so the percentage of vanadium was increased from 9 to 12%. This value was fixed and other elements were varied.

Stainless steel with the designation S125V was developed in 2004. It was clear that research into improving its parameters by changing the composition was ongoing. The patented version had slightly less than 3% carbon, 13.5% chromium and 2.7 percent molybdenum. However, in the final release of the brand, carbon was already 3.3%, and the chromium content increased to 14%. Molybdenum, on the contrary, was reduced to 2.5%. It is known that nitrogen is present in the steel, but the company does not disclose the actual percentage value of this element. The result is a very hard steel. Compared to S90V steel, the S125V grade has a higher cutting edge resistance, but lower strength.

Advantages of CPM S125V stainless steel

• The main advantage is increased hardness and strength: this gives buyers an exceptionally durable knife from the category of those that are bought once for a lifetime with the prospect of passing it on to children. Powder metallurgy technology allows obtaining a homogeneous alloy with a hardness after heat treatment of 59-65 HRC, which ensures the sharpness of the cutting edge for a long period.
• CPM S125V is highly resistant to corrosion: according to knife owners, this is a true stainless steel (however, long-term use in a humid and salty environment without proper care can cause unpleasant surprises even for this grade).
• Edge Retention: the steel holds an edge well. Only the CPM MagnaCut brand can beat the CPM S125V in edge retention.

More and more knife makers are moving away from CPM S125V in recent years, primarily because of the difficulty of finishing. Custom knifemaker Phil Wilson said that hand-satining S125V took three times longer than CPM 10V, one of the heaviest steels in the mass market.