S35VN vs M390 Steel

S35VN was developed by Crucible Industries as part of their Crucible Particle Metallurgy (CPM) series of advanced steels. 

S35VN was designed as a toughened modification of the popular CPM S30V steel, reducing vanadium content while adding niobium to enhance toughness.

On the other hand, M390 was pioneered by the Austrian company Böhler under their MICROCLEAN powder metallurgy process and sold as BÖHLER M390.

In the US market, Bohler M390 steel was initially copied and sold as 20CV by Latrobe Steel and by Carpenter as CTS-204P.

The key difference between these premium steels is that S35VN leans towards providing superior toughness and ease of sharpening compared to M390. 

In contrast, M390 is optimized for exceptional wear resistance, edge retention, and corrosion resistance due to its high chromium content and large proportion of hard vanadium/chromium carbides. 

S35VN vs M390 Steel At A Glance

Hardness

M390 has a higher potential hardness compared to S35VN. The datasheet for S35VN shows a maximum hardness of around 64 HRC after optimal heat treatment.

In contrast, the data from Bohler-Uddeholm indicates that M390 can reach hardness values over 66 HRC, particularly when using a sub-zero treatment after hardening followed by multiple temper cycles. 

The higher attainable hardness of M390 suggests it can provide better edge retention and wear resistance in knives compared to S35VN. 

Toughness

When it comes to toughness, the data shows that S35VN has a clear toughness advantage over M390.

Independent toughness testing results indicate that at similar hardness levels around 62 HRC, S35VN exhibits superior toughness compared to M390.

Specifically, in the Charpy V-notch tests, S35VN had an average toughness value of around 17 ft-lbs, while M390 was lower at only around 12 ft-lbs. 

This higher toughness of S35VN translates to better resistance to chipping and breaking when knives made from this steel encounter side loads or impacts during use.

In contrast, the relatively lower toughness of M390 means knives made from this steel, especially those with very thin edges, are more prone to chipping and catastrophic edge failure. 

For applications where exceptional edge stability and robust performance are priorities, such as for heavy-duty or survival knives, S35VN would be the preferred choice over M390 due to its superior toughness.

Edge Retention

In terms of edge retention and wear resistance, M390 holds a distinct advantage over S35VN steel.

Multiple independent CATRA test results show that M390 steel outperforms S35VN steel in edge-holding ability.

Bohler CATRA Edge Retention Test results show that M390 at 61HRC scored 958.6 for Total Cards Cut (TCC), while S3VN at 61HRC scored 706.6, indicating M390 has superior edge retention capability.

The higher edge retention of M390 can be attributed to its greater volume fraction of hard vanadium and chromium carbides compared to S35VN.

For knives, this means that M390 blades can hold their sharpness for longer under equivalent cutting tasks before needing re-sharpening. 

S35VN still offers good overall edge performance, the superior wear resistance of M390 makes it the preferred choice when extreme edge longevity and reduced sharpening frequency. 

Ease of Sharpening

S35VN blade steel has an advantage over M390 blade steel in ease of sharpening and grindability. 

While both are powder metallurgy stainless steels, the lower overall carbide volume and lack of the extremely hard vanadium carbides present in M390 makes S35VN easier to abrade and sharpen.

Micrographs show that S35VN has a finer, more uniform carbide distribution compared to the coarser chrome/vanadium carbide network in M390.

This finer structure, combined with substituting some of the vanadium for softer niobium carbides, allows S35VN to be sharpened more efficiently with aluminium oxide abrasives used for knives.

In contrast, M390 high vanadium content and large chromium carbides make it more resistant and slower to grind and sharpen, especially with aluminum oxide wheels or stones. 

Corrosion Resistance

Bohler M390 and CPM S35VN are both stainless steels with excellent corrosion resistance.

However, M390 exhibits superior corrosion resistance performance compared to S35VN steel. 

The exceptional corrosion resistance of M390 can be primarily attributed to its very high chromium content of 20% compared to only 14% in S35VN.

This high chromium, combined with 1% molybdenum in M390, promotes the formation of a robust passive chromium oxide layer that enhances resistance to corrosion, staining and rust. 

For knives, the superior corrosion resistance of M390 makes it more suitable for use in environments with an increased risk of staining, pitting, and rust formation. 

While S35VN still offers decent corrosion performance, M390’s improved resistance provides better corrosion preservation when knives are subjected to harsh, corrosive environments.

Final Thoughts on S35VN vs M390 Steel

In my experience working with these premium powder metallurgy stainless steels, I highly recommend S35VN over M390.

While M390 does outperform S35VN in terms of edge retention and corrosion resistance, the differences are relatively small and unlikely to be highly noticeable in daily use for most knife owners.

Where S35VN steel truly shines is in its exceptional toughness and superior ease of sharpening and grinding.

The advancement in S35VN alloy is impressive, as Crucible was able to significantly enhance the toughness over S30V while maintaining good wear resistance, and corrosion resistance. 

This outstanding balance of key properties makes S35VN incredibly versatile and user-friendly for knives across various tasks and conditions.

Unless you require the absolute maximum edge-holding ability or corrosion performance that M390 offers, the added toughness and sharpening advantages of S35VN make it the better choice,