S30V vs S35VN Steel

CPM S30V and CPM S35VN are two premium knife steels developed and produced by Crucible Industries through CPM (Crucible Particle Metallurgy).

These martensitic stainless steels share a close relationship, as S35VN is a modified version of the original S30V steel.

S35VN is designed to offer enhanced toughness and improved machinability.

While both S30V and S35VN excel in various properties crucial for high-performance knives and blades, the key difference lies in their composition. 

S35VN was engineered with a reduced vanadium content (3% compared to 4% in S30V) and the addition of 0.5% niobium, resulting in a steel with superior toughness and ease of machining/grinding.

This strategic alteration in alloy allowed S35VN to retain the exceptional wear resistance and corrosion resistance similar to the S30V while offering improved resistance to chipping and breaking.

S30V vs S35VN Steel At A Glance

Toughness

S35VN exhibits superior transverse toughness compared to S30V, with a Charpy C-notch impact energy of 12 ft-lbs versus 10 ft-lbs for S30V.

The key difference in toughness between S30V and S35VN lies in the modified alloy of S35VN, which was designed to improve toughness over its predecessor, S30V.

This enhanced toughness in S35VN is achieved by reducing the vanadium content from 4% to 3% and introducing 0.5% niobium.

The niobium addition promotes the formation of niobium carbides alongside vanadium and chromium carbides, resulting in a more refined and tougher microstructure. 

The improved toughness of S35VN steel translates into better resistance to edge chipping and breaking, especially in larger blades or knives that may encounter side loading or impact forces. 

This makes S35VN a more suitable choice for larger knives including kitchen or applications where toughness is a critical requirement.

Hardness

There is a slight difference in hardness attainability between S30V and S35VN steels. S30V has the potential to achieve slightly higher hardness levels compared to S35VN.

S30V can reach hardness values up to 64 HRC when properly heat-treated, while S35VN can reach up to 63.5 HRC.

However, the heat treatment response charts show that with certain austenitizing temperatures and tempering, both steels can achieve a maximum hardness of around 64 HRC.

The slightly lower hardness attainability of S35VN can be attributed to its lower vanadium content (3% compared to 4% in S30V) and the addition of 0.5% niobium.

Niobium results in a slightly lower volume fraction of hard vanadium carbides (MC) compared to S30V.

The difference in maximum hardness between the two steels is relatively small and may not have a significant impact on edge retention or wear resistance for knives.

Edge Retention

CPM S30V Steel exhibits better edge retention and wear resistance than CPM S35VN steel due carbide compositions.

S30V with its higher vanadium content of 4%, forms a higher volume fraction of hard vanadium carbides (MC), which contribute significantly to improved wear resistance and edge retention.

According to the CATRA (Cutlery & Allied Trades Research Association) testing, which measures the number of silica-impregnated cards cut as an indicator of relative wear resistance.

Bohler-Uddeholm CATRA tests showed S30V steel at a hardness of 61 HRC achieved a TCC edge retention of 798 while S35VN at a hardness of 61HRC achieved a TCC edge retention of 706.6.

Crucible data lists S30V exhibits superior edge retention at 145% compared to the standard 440C stainless steel,  and lists S45VN also at 145%* based on market feedback. 

However in real life test S35VN, with its reduced vanadium content of 3% and the addition of 0.5% niobium, is estimated to have an edge retention of around 132-140% of 440C.

S30V knife steel may be the preferred choice when edge retention and wear resistance are the primary considerations, as it can maintain a sharper edge for longer and better withstand abrasive wear during use.

S35VN offers a balance between toughness and wear resistance, making it a suitable option for knives where both characteristics are desirable,

Corrosion Resistance

CPM S35VN steel and CPM S30V steel are both martensitic stainless steels with excellent corrosion resistance.

S35VN and S30V steels exhibit comparable corrosion resistance properties, making them suitable choices for knives and other cutting tools that may be exposed to corrosive environments.

According to the pitting potential measurements conducted in a 5% sodium chloride (NaCl) solution, both steels demonstrated similar corrosion resistance levels.

The data indicates that S35VN and S30V have nearly identical pitting potentials, suggesting their ability to resist pitting and crevice corrosion in chloride-containing environments is comparable.

The corrosion resistance of these martensitic stainless steels is primarily derived from their high chromium content, which is around 14% for both alloys.

This chromium content promotes the formation of a passive oxide layer on the surface, providing protection against corrosive attacks.

For knife applications, the comparable corrosion resistance of S30V and S35VN makes them suitable for use in various environments, including those with potential exposure to moisture, salt, or other corrosive agents.

Ease of Sharpening

In terms of ease of sharpening and grindability, S35VN offers a distinct advantage over S30V due to its modified chemistry and reduced volume fraction of hard vanadium carbides.

Crucible datasheets indicate that S35VN knife steel is much easier to machine and grind compared to S30V knife steel. 

This superior machinability and grindability can be attributed to the reduced vanadium content (3% in S35VN vs. 4% in S30V) and the addition of 0.5% niobium in S35VN.

The lower volume of hard vanadium carbides (MC) in S35VN makes it less abrasive on grinding wheels and sharpening stones, resulting in improved grindability and easier sharpening.

The easier sharpening characteristics of S35VN can be advantageous for end-users, as it requires less effort to maintain a sharp edge, reducing the risk of damaging the blade or sharpening equipment.

While S30V offers superior wear resistance and edge retention due to its higher vanadium carbide content, the trade-off is increased difficulty in sharpening and grinding.

Final Thoughts on S30V vs S35VN Steel

Having had extensive experience with both S30V and S35VN knife steels through my use of pocket and kitchen knives made from these steels, I can confidently vouch for their exceptional qualities.

The impressive edge retention and corrosion resistance in both steels have consistently impressed me, making them excellent choices for high-performance knives.

However, the key difference between S30V and S35VN lies in the S35VN enhanced toughness and improved ease of sharpening.

By reducing the vanadium content and introducing niobium, S35VN retains the core strengths of wear resistance and corrosion resistance while offering superior resistance to edge chipping. 

From my personal experience, the standout benefit of S35VN is its improved machinability and grindability, which translates to a more user-friendly sharpening process. 

S35VN modified alloy makes it less abrasive on sharpening stones and grinding wheels, allowing for more efficient edge maintenance and refinement.

S35VN ease of sharpening is a significant plus for someone like me who frequently sharpens their knives.

While both S30V and S35VN are exceptional knife steels, I would highly recommend S35VN for most users due to its better ease of sharpening and toughness.