S30V and SPY27 are two premium stainless steels made by Crucible Industries for use in knives.
CPM S30V knife steel was originally developed in collaboration with Spyderco and Chris Reeve Knives in the early 2000s to improve upon existing stainless steels like 154CM.
CPM SPY27 is a relatively new steel created by Crucible as an S30V variant exclusive to Spyderco Knives to further improve grindability and ease of sharpening.
Both knife steels contain similar levels of chromium for good corrosion resistance, along with significant vanadium, and molybdenum additions for excellent wear resistance.
However, SPY27 reduces the overall carbide content compared to S30V through lower carbon and vanadium, which improves toughness and grindability.
SPY27 offers modest improvements in grindability over S30V while maintaining many of the same properties.
SPY27 vs S30V At A Glance
| Property | SPY27 Steel | S30V Steel |
|---|---|---|
| Hardness | 64 HRC | 64 HRC |
| Edge Retention | Very good | Slightly better than SPY27 due to higher carbide content |
| Ease of Sharpening | Better than S30V | More difficult than SPY27 due to higher carbide content |
| Toughness | Slightly better than S30V | Slightly lower than SPY27 |
| Corrosion Resistance | Very good | Slightly better than SPY27 |
Hardness
SPY27 and S30V have very similar hardness levels, with both capable of being heat treated to around 64 HRC with cold treatments like liquid nitrogen.
The high hardness of both steels is achieved through their carbides, with SPY27 forming both Niobium and vanadium carbides while S30V having more overall carbide content.
SPY27 steel utilizes Niobium additions as a carbide former to improve the hardness and wear resistance.
SPY27 and S30V knife steels can reach comparable hardness levels when optimized, providing excellent edge retention and wear resistance for knives.
Edge Retention
S30V knife steel has slightly better edge retention and wear resistance compared to SPY27 knife steel.
This is attributed primarily to S30V’s higher overall carbide content, with S30V containing 4% vanadium carbides versus 2.75% in SPY27.
The higher carbide content in S30V provides increased wear resistance and edge retention.
However, the difference in edge retention between the two steels is not very large, as SPY27 forms more refined carbides than S30V due to presence of niobium that typically acts as a carbide former.
For knives, the edge retention advantage of S30V means it can maintain sharpness slightly longer under extended cutting use.
But SPY27 still provides excellent wear resistance and edge retention suitable for most cutting applications.
Ease of Sharpening
SPY27 steel has slightly better grindability and is easier to sharpen compared to S30V steel.
This can be attributed to SPY27 steel lower overall carbide content and reduced amount of vanadium carbides.
The higher carbide content in S30V increases abrasion resistance which consequently makes it more difficult to abrade and sharpen.
The improved grindability of SPY27 knives means it may require less effort to put an initial sharp edge versus S30V.
Toughness
Toughness is the ability of knife steel to resist chipping, cracking, or breaking under impact.
Impact toughness testing shows that SPY27 has slightly higher toughness than S30V, with SPY27 reaching around 7.5-8.5 ft-lbs, while SPY27 scored around 5.5 ft-lbs.
SPY27 steel toughness is slightly better than S45VN and S30V steel but slightly lower than S35VN steel.
The higher toughness of SPY27 makes SPY27 knives more resistant to chipping and allows thinner edge geometries compered to SPY27 Knives.
Corrosion Resistance
SPY27 and S30V are stainless steels with very good corrosion resistance.
However, S30V steel exhibits slight better corrosion resistance than SPY27 steel.
Pure and Saltwater corrosion testing done by Dr.Larrin Thomas indicates that S30V steel has slightly better corrosion resistance compared to SPY27 steel.
However, the difference in corrosion resistance between the two steels appears relatively small, with both steels passing the purified water spray test with no pitting.
In the 1% saltwater spray test, S30V exhibited marginally less corrosion than SPY27.
The cobalt addition in SPY27 may play a minor role in reducing corrosion resistance compared to S30V.
Final Thoughts SPY27 VS S30V
Having great experience with both S30V and SPY27 steels, I can say that S30V has been my go-to choice for a long time due to its incredible edge retention capabilities.
The high vanadium carbide content gives S30V superior abrasion resistance and edge-retention. However, for Spyderco knives, I would highly recommend SPY27 over S30V.
From my testing, SPY27 offers slightly improved toughness over S30V along with better ease of sharpening.
These advantages come from SPY27’s refined carbide content and lowered carbon and vanadium in composition.
While S30V still maintains better edge retention, and corrosion resistance on paper, the small improvements in toughness, and sharpening make SPY27 a better all-around choice for Spyderco’s knives.
For me, SPY27 represents an upgrade that builds upon the proven performance of S30V. I find it an excellent stainless steel that combines S30V’s strengths with better ease of sharpening.