SPY27 vs S45VN Steel

S45VN and SPY27 are two powder metallurgy stainless steels made by Crucible Industries through the powder metallurgy process which results in a fine, consistent carbide structure and superior properties compared to conventional steels.

CPM S45VN was developed by Crucible as an improvement over CPM S35VN and S30V steel with higher wear resistance thanks to increased vanadium and niobium content. 

SPY27 is a relatively new steel that was developed jointly by Crucible and Spyderco as an exclusive steel for Spyderco knives. It contains additions like cobalt and niobium to enhance properties. 

S45VN and SPY27 have similarities in their properties but S45VN steel may have slightly better wear resistance and edge retention while SPY27 offers higher corrosion resistance.

S45VN has been utilized by several top knife makers for its combination of hardness, edge retention, and corrosion resistance. 

SPY27 vs S45VN Steel At A Glance

Hardness

The hardness of S45VN and SPY27 steels is very similar when properly heat treated, with both capable of reaching over 64 HRC according to crucible datasheets.

The high hardness is achieved through the addition of strong carbide formers like vanadium, niobium, and chromium along with sufficient carbon. 

For knife performance, these high hardness values enable excellent edge retention and resistance to abrasive wear. However, the high hardness also means the steels are relatively brittle.

This limits the toughness and makes the steels best suited for thinner, smaller knife blades rather than very large chopping tools.

But for most folding knives, fixed blade knives, and kitchen cutlery, the high hardness achieved by S45VN and SPY27 provides superior edge holding compared to lower alloy steels while also maintaining good corrosion resistance.

With appropriate knife designs, the high hardness ratings of S45VN and SPY27 can be fully utilized to maximize cutting performance. 

Toughness

Testing shows SPY27 exhibits slightly better toughness compared to S45VN and S35VN which can provide more durability under hard use for properly designed knife blades.

The higher toughness also makes SPY27 a better choice for larger knife blades that experience higher bending stresses during use.

SPY27 thus offers enhanced resistance to chipping and cracking under abusive cutting situations.

The microstructures reveal both steels have some carbide clusters which may limit the toughness.

The marginally improved toughness of SPY27 is attributed to its lower overall carbide content and finer, more evenly dispersed carbides compared to S45VN and S35VN.

Edge Retention

S45VN and SPY27 both offer excellent edge retention and wear resistance due to their high hardness and the large volume of vanadium carbides. 

However, S45VN steel likely has slightly better edge retention and wear resistance than SPY27 steel. 

CATRA testing shows S45VN steel has about 43% better retention than 440C steel which is 3% better than S35VN steel. 

SPY27 is estimated to have slightly less edge retention compared to S35VN based on lower vanadium and niobium content. 

SPY27 does maintain good wear resistance but S45VN is likely ahead by a small margin.

These performance advantages mean knives made with S45VN and SPY27 will retain their sharp edges better than most other cutlery steels during extended cutting tasks.

Knives in these steels will require less frequent sharpening compared to lower alloy steels like 440C.

However, the difference in actual cutting performance between S45VN and SPY27 is likely quite small and not very significant for most users. 

Corrosion Resistance 

Both SPY 27 and S45VN are stainless steel, however, corrosion resistance testing shows that SPY27 exhibits better corrosion resistance compared to S45VN steel.

Although both contain significant chromium, crucible cpm SPY27 has a higher chromium content at 14.5% versus 11.5% for S45VN. 

Testing indicates that SPY27 performs similarly to S30V steel, which rates as having “good” or “above average” corrosion resistance among knife steels.

In comparison, the lower chromium S45VN stainless steel likely has marginally inferior corrosion properties to SPY27 stainless steel.

For knives, the level of corrosion resistance provided by S45VN and SPY27 means the steels can be used for most EDC tasks, but may show some pitting or staining if not properly maintained.

For diving or saltwater knives, S45VN or SPY27 would not be the best choice compared to steels like H1 or LC200N which have exceptional corrosion resistance.

But with proper care, both S45VN and SPY27 can provide good corrosion resistance for a variety of knife applications while also offering excellent edge retention and wear resistance.

Ease of Sharpening

SPY27 likely has a slight advantage in sharpening over S45VN. The lower overall carbide content of SPY27 compared to S45VN suggests it will be slightly less abrasion-resistant when grinding and honing an edge.

SPY27 also contains cobalt, which is known to improve machinability in tool steels. However, SPY27  and S45VN are considered fairly difficult to sharpen due to their high hardness and large volume of abrasion-resistant carbides. 

The high alloy content that provides excellent edge retention also causes the steels to be somewhat wear-resistant during the sharpening process.

This means edges made from SPY27 steel should be a bit easier to re-sharpen compared to S45VN steel. However, the difference is probably quite small.

In general, both steels will require diamond or CBN sharpening stones to effectively reshape the edge once dull.

While not the easiest to sharpen, the outstanding cutting performance provided by S45VN and SPY27 makes the additional effort worthwhile for critical cutting applications.

Final thoughts on SPY27 vs S45VN Steel

S45VN and SPY27 represent two excellent stainless steel choices for knife makers and users demanding high hardness, edge retention, corrosion resistance and wear resistance.

I have personal experience with and have been a big fan of S30V and S35VN over the years. These Crucible-made powdered steels have proven performance in many of my favorite knife designs.

While I have yet to gain sufficient firsthand experience with SPY27 steel, it appears impressive on paper and testing thus far.

The joint development between Crucible and Spyderco means SPY27 is not likely to disappoint in real-world use.

It offers a unique balance of properties, with perhaps slightly better corrosion resistance and toughness than S45VN, at the cost of a small degree of edge holding.

However, S45VN remains a proven winner with hundreds of top knife models over the past decade. Its combination of hardness, edge retention, corrosion resistance and toughness is hard to beat.

For users who tend to be hard on their knives, SPY 27 steel provides that extra degree of toughness and longevity.

The similarities between S45VN and SPY27 mean that personal preference may play a large role when choosing between the two.