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CPM 154 and S30V are both stainless steels made using the Crucible Particle Metallurgy (CPM) process pioneered by Crucible Industries.
CPM 154 was developed as an improvement over 154CM, an ingot cast stainless steel, by providing better toughness.
CPM S30V steel, released later, contains higher vanadium content to increase wear resistance compared to 154CM and CPM 154.
S30V knife steel offered a good balance of properties and became widely used in most knives.
More recently, S35VN and S45VN have been developed by Crucible as successors to S30V to provide further improvements in wear resistance, corrosion resistance, and toughness.
S30V demonstrates the highest attainable hardness out of these three stainless steels due to its higher alloy content and carbide volume.
S30V contains 4% vanadium which facilitates substantial hard vanadium carbide formation, allowing it to reach hardnesses up to 64 HRC with optimal heat treatment.
CPM 154 follows with a working hardness of around 62 HRC, as its lack of vanadium carbides means its hardness depends on the chromium carbide content alone.
However, CPM 154 still achieves higher hardness than conventionally processed 154CM stainless steel.
The fine carbide size and homogeneous distribution of CPM 154 from powder metallurgy production give it an advantage over ingot-cast 154CM.
S30V stands out with the highest hardness potential due to its significant volume of hard vanadium carbides.
CPM 154 reaches moderately high hardness relying solely on chromium carbides, while 154CM is slightly softer than both powder metallurgy steels due to its conventional production method resulting in a more coarse carbide structure
The higher the attainable hardness of steel results in better wear resistance and edge retention when used in a knife.
Toughness in knife steel is the ability to resist chipping, cracking, or breaking under impact or heavy use.
Out of S30V, CPM 154, and 154CM steels, CPM 154 steel has the highest toughness, followed by 154CM and S30V.
CPM 154 steel lack of hard, brittle vanadium carbides gives it an advantage in toughness over S30V.
The powder metallurgy production of CPM 154 results in a finer, more homogeneous distribution of chromium carbides compared to conventionally processed 154CM, further improving its toughness.
Testing shows CPM 154 knife steel achieves excellent impact toughness around 25-28 ft-lbs longitudinally.
Meanwhile, 154CM knife steel reaches about 20 ft-lbs, with its coarser as-cast carbide structure reducing toughness somewhat compared to powder CPM 154.
S30V trails both with low impact toughness due to its higher overall carbide content including the presence of hard vanadium carbides.
CPM 154 steel lack of vanadium carbides coupled with its fine carbide size from CPM production gives it the best combination of hardness and superior fracture resistance compared to 154CM and the harder, more wear-resistant S30V.
S30V steel demonstrates the best corrosion resistance out of these three stainless steels due to its optimized microstructure and beneficial alloying additions.
The 2% molybdenum and 0.2% nitrogen in S30V improve pitting and crevice corrosion resistance.
S30V also forms less chromium carbide than CPM 154 or 154CM, leaving more chromium dissolved in the matrix to enhance corrosion resistance.
Testing shows that S30V exhibits very few rusting spots than CPM 154 and 154CM in salt spray testing.
The fine, homogeneous carbide distribution in S30V from powder metallurgy production provides another advantage over conventionally processed 154CM.
Between CPM 154 and 154CM, CPM 154 exhibits moderately better corrosion resistance from its finer carbide structure.
But S30V stands out as having the most robust corrosion resistance due to its alloy and microstructure that optimize stainless properties.
However, all three steels still provide decent corrosion resistance suitable for many applications.
Out of S30V, CPM 154, and 154CM stainless steels, CPM 154 has the best grindability and allows for the easiest sharpening due to its finer and lower carbide volume.
The lack of hard, abrasion-resistant vanadium carbides in CPM 154 prevents excessive wear on grinding belts and stones.
CPM 154 also forms less carbide overall compared to the higher alloy S30V steel.
Between CPM 154 and 154CM, CPM 154 is easier to grind and sharpen owing to its finer, more homogeneous carbide distribution from powder metallurgy production versus the coarser as-cast structure of 154CM.
However, S30V steel is the most difficult to grind and sharpen by a significant margin. The high volume of fine vanadium carbides in S30V causes rapid dulling of abrasives.
Machinability data shows that S30V is comparable to very wear-resistant tool steels like D2.
While S30V offers superior edge retention, this comes at the cost of much greater difficulty sharpening and refining the edge due to its extreme abrasion resistance.
For ease of maintaining the edge, CPM 154 knife steel is the best choice of these three steels.
Having used all three of these stainless steels in various knives over the years, I’ve developed preferences for specific applications based on their differing properties.
If I want a knife with extreme edge retention for hard use, I reach for S30V every time.
The high volume of vanadium carbides makes S30V steel significantly more wear-resistant than CPM 154 or 154CM.
Among the first budget knives that I bought was made of 154CM steel, I always loved the way it took a sharp edge on normal sharpening tools.
You will not go wrong with any of these three blade steels, but I highly recommend CPM 154 steel due to its more balanced properties and ease of sharpening.
Like Kawr said, it's similar to VG-10. Although in my experiance VG-10 holds an edge slightly better. I actually would probably take 154cm over S30V as I sometimes have troubles trying to get the edge I want with S30V as it's harder to sharpen. 154CM is a good working knife steel, certainly not crap by any means.
Those who choose to live a life without risks, arrive safely at death's door.
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