CTS XHP and S35VN are steels made using powder metallurgy processes that offer a good balance of properties for knife applications.
CTS XHP steel was developed by Carpenter Technology as a higher hardness alternative to 440C stainless steel.
XHP uses a composition similar to D2 tool steel but with increased chromium for better corrosion resistance.
CPM S35VN steel was created by Crucible Industries to improve upon their existing CPM S30V steel.
S35VN reduces the vanadium carbide content and adds niobium to improve toughness and machinability compared to S30V.
The key differences between CTS XHP and S35VN come down to their intended purposes.
CTS XHP prioritizes hardness and wear resistance. It can reach 65 HRC hardness giving it excellent edge retention.
S35VN focuses more on improved corrosion resistance while still maintaining good hardness and wear resistance.
CTS-XHP vs S35VN At A Glance
| Property | CTS XHP Steel | S35VN Steel |
|---|---|---|
| Hardness | 1-1.5 HRC higher (up to 65 HRC) | Up to 64 HRC |
| Edge Retention | Slightly better (~12%) | Very good |
| Ease of Sharpening | Better due to lower vanadium | Good |
| Toughness | Very good when properly heat treated | Very good when properly heat treated |
| Corrosion Resistance | Good | Better than XHP steel |
| Composition | 1.6% C, 16% Cr, 0.8% Mo, 0.45% V | 1.4% C, 14% Cr, 2% Mo, 3.0% V |
| Key Properties | Maximizes hardness and wear resistance | Balances toughness and corrosion resistance |
Hardness
CTS XHP steel has higher attainable hardness compared to S35VN steel. Specifically, the datasheet for CTS XHP steel shows it can reach hardness values up to 64 HRC.
The heat treatment response chart also confirms hardness values up to 65 HRC are possible. In contrast, the datasheet for S35VN steel indicates a maximum hardness of 63.5 HRC.
The heat treatment response chart for S35VN shows hardness values up to 64 HRC are possible. Therefore, CTS XHP steel can attain 1-1.5 HRC higher hardness compared to S35VN steel.
This higher hardness potential gives CTS XHP an advantage in terms of wear resistance and edge retention in knives.
The higher hardness also allows for a wider range of heat treatment options to tailor the hardness to the desired knife application.
Edge Retention
CTS XHP steel has slightly better edge retention and wear resistance compared to S35VN steel for knife applications.
Directly comparing the wear resistance testing results indicates CTS XHP has about 12% better wear resistance than S35VN.
This can be attributed to the higher attainable hardness of CTS XHP, allowing it to reach 65 HRC vs 63.5 HRC maximum for S35VN.
CTS XHP has a higher total carbide content at 21% vs 14% for S35VN. The increased amount of hard carbides contributes to increased wear resistance for CTS XHP.
Specifically, CTS XHP achieved a volume loss of 35 mm3 in dry sand rubber wheel testing per ASTM G65.
In comparison, S35VN is estimated to have 132% of the wear resistance of 440C steel, which correlates to around 40 mm3 volume loss.
For knives, the better wear resistance provides CTS XHP with slightly improved edge retention during cutting usage.
However, both steels exhibit very good edge retention due to their high hardness and carbide volumes.
Ease of Sharpening
CTS XHP steel has better ease of sharpening and grindability compared to S35VN steel for knife applications.
CTS XHP contains lower amounts of vanadium carbides which are harder and more difficult to grind than chromium carbides.
S35VN steel contains 3% vanadium carbides compared to only 0.45% vanadium in CTS XHP steel.
In direct comparison, the lower vanadium carbide content in CTS XHP makes it easier to sharpen and grind compared to the higher vanadium S35VN steel.
Additionally, CTS XHP is easier to hand finish compared to high vanadium steels like S30V and S90V, which contain even more vanadium than S35VN.
The improved ease of grinding and sharpening gives CTS XHP knives advantages during manufacturing, re-sharpening, and maintenance over S35VN knives.
Toughness
Toughness is the ability of a knife to resist, cracking, chipping, or breaking under impact.
CTS XHP and S35VN steels have very similar toughness when properly heat-treated for knife applications.
The Charpy impact toughness values show S35VN achieves 12 ft-lbs while CTS XHP ranges from 10 ft-lbs depending on exact hardness.
However, this testing was done at different hardness levels, with S35VN at 57-61 HRC and CTS XHP at 60-64 HRC.
Accounting for the hardness difference, the toughness of these two steels is quite comparable, especially when optimally heat treated. The high-hardness steels become brittle if improperly heat treated.
Additionally, the microstructures of CTS XHP and S35VN are both fine grained with evenly distributed carbides when properly processed. This contributes to their good toughness capabilities.
For knives, the toughness of both these steels is sufficient when heat treated for an optimum balance of hardness and toughness.
Corrosion Resistance
S35VN and CTS XHP have good corrosion resistance, however, S35VN steel has substantially better corrosion resistance compared to CTS XHP based on alloying content, and corrosion testing.
The improved corrosion performance of S35VN gives it significant benefits for knife blade applications needing high stain and rust resistance.
S35VN steel corrosion resistance is improved by the presence of lower chromium carbides as compared to a higher amount of chromium carbides in CTS XHP.
S35VN stainless steel also has higher Molybdenum content at 2% versus 0.8% for CTS XHP steel.
S35VN achieved over 200 millivolts higher pitting potential than 440C steel in ASTM corrosion testing.
In comparison, the CTS XHP data sheet rates its corrosion resistance as equivalent to 440C at about 50 millivolts.
Furthermore, the higher attainable hardness of CTS XHP steel indicates lower chromium left in solution to fight corrosion compared to S35VN with a lower hardness.
For knives, the better corrosion resistance provides S35VN with increased stain and rust resistance when exposed to moisture, acids, salt, etc. during use and maintenance.
Final Thoughts on CTS-XHP vs S35VN
In summary, you can’t go wrong selecting either CTS XHP or S35VN stainless steel for your knife.
Having experience with both steels, I find CTS XHP to be an underrated and well-balanced steel that deserves more popularity in the knifemaking world.
CTS XHP offers a superb combination of wear resistance and edge retention yet it remains very sharpenable due to lower vanadium content.
However, S35VN steel does have slightly better corrosion resistance due to its higher chromium content.
This may make S35VN steel a more appealing choice for applications where corrosion is a major concern.
The popularity of S35VN over CTS XHP steel likely comes down to wider commercial availability.
S35VN is produced by Crucible Steel Company which has the capacity to make it easier to obtain for most knifemakers.
In contrast, CTS XHP has had some availability issues which has led companies like Cold Steel to discontinue using it in the past.