Well the user is in full control of the edge Geometry, degrees of angle and flat vs Convex. Lower flatter angles cut more, thicker convex edges are more durable.
On paper M390 seemed to be the top dog for production knives. Yet it didn't add up always.
Some backstory.
2019 a group of testers came together to try to and understand why they were all getting low numbers for their cut testing with what should be superior steel. They noticed the edge retention was dismal to S30v etc. They then sought further testing, They were able to get the knives HRC tested and noticed low Rockwell values and caused quite an upset in the community.
After they were dismissed for being "BroScience" they find raised money to send out production knives for more Scientific testing to CATRA in the UK. Three folders in M390 and a one in S30v for control. All the m390 was from different companies and hardness from 58-62rc
Well, the CATRA showed that when the HRC was low on the M390 (58rc) it underperformed S30v (61rc) that was slightly harder.
Even though s30v has a lower total volume of carbide. M390 is mostly chromium carbide (17.5%) and less volume of the more effective Vanadium carbide (2.5%)
Compared to S30v (10.5%) chromium carbides and (4%) Vanadium Carbides
When the M390 was at the same hardness as S30V, M390 cut more.
M390 is not like S90v which can cut longer at slightly lower HRC in controlled wear cut testing since it has more of the harder Vanadium Carbides (9%) and (13%) chromium carbides.
Yet, folks love M390 and many claim it sharpens better and holds a longer edge for them real world vs S30v. Could be a mix of placebo or the fact that it just gets sharper with THEIR tools and techniques with less Vanadium carbides to cut through to shape the apex. Who knows.
So I find it silly to dismiss a steel like SPY27. For not having enough carbide volume. How everything works is more complex.
When you bottom out the hardness on the M390, all that wear resistance on paper didn't add up to edge retention one would expect yet you still get all the detriments of those carbide reducing the edge stability and tougheness. Carbides are tiny hard inclusions in the steel that can promote the edge to be more brittle since they are brittle particles themselves but also serve to act as areas crack initiation. Cracks will connect the dots through the carbides and cause blow out vs lower volume is less prone.
So high carbide steels under 59rc are the worst of both worlds.
For example, I wouldn't dare make a custom in Rex 121 at 58 rc to make tougher. At 30% carbide volume toughness is going to suck anyways and the Stability will be bottomed out for impact toughness not edge toughness, matrix is too soft to hold those Carbides so they can resist wear when the matrix that holds them is soft. My point is lower HRC doesn't make something designed for other applications edge tough/stable
I suppose manufacturers need to stop being scared and bump the hardness and deal with the warranty fall out from those that refuse to use them properly and move those folks to another steel. 3v at 56rc lmao jk but you can see the fundamental problem in the community and it's not just the steel, its the audience too.
Now some folks can't handle this level of detail and the duality between the different things I'm describing and will think I'm saying Carbides are the devil.
No.
A steel devoid of Carbides will wear smooth faster even at high 66 HRC and just doesn't have that edge aggression folks like for edge that grab and bite ferociously.
So in reality, you're damned if you do, damned if you don't.
If you want the same Edge Retention from high carbide steels you see in controlled testing in real world you need to step your game up, use proper stones and sharpening techniques and use it like a knife, not a toliet wand.
I've always been one to point out the trade offs involved with carbides and that they are a necessary evil if you want the maximum hardness and cutting retention in a controlled environment. Yet, in the real world, since people are all over the place with sharpening and use, it just doesn't always seem to translate to everyone or everything so it's nice to have options for people.
Vanax Superclean was supposed to be similar to Elmax in wear resistance on paper. Yet, in real world, it destroys Elmax for people and always tests high in social media cut testing and with users.
So, there is a lot going here and I'd like if folks could appreciate it.
Otherwise y'all need to only use s125v and Rex 121 cause In testing nothing out cuts those steels, not even Vanax unless the sharpening isn't good.
I am okay with that too. I love those steels
Do you seriously think Spyderco will change the geometry of the Para 2 blade (grind, edge) in order to perfectly exploit the new steel?
Of course not. They will just sell a standard Para 2 with the new steel, that's all. It will not be thinner.
And if the geometry does not change then perhaps another stainless steel (M390) is a better choice ?
