M390 and 20CV Edge Breakdown (59HRc vs. 61HRc)
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- เผยแพร่เมื่อ 3 ก.ค. 2021
- In my "How to PM Steels Break Down" video I discuss the transition from fine edge to working edge in PM steels and hypothesized how hardness effects the breaking down of the edge. To anecdotally investigate this I compared a Benchmade 940 in 20CV at 59HRc and a Spyderco Para 3 in M390 @ 61HRc (hardness is estimated from cut tests and other knives that have been tested). These steels are analogs of each other so the test would mostly reflect the difference in heat treat. These differences are namely hardness, total carbide volume and grain size (the latter was not studied).
Both were sharpened on a naniwa chosera 800, 3K and stropped with 1um diamond on wood. Resulting edges were around 150g BESS. They were used on and off for about a month until they both developed a full working edge which coincided with 350g - 400g BESS scores. At that point all of the initial refined bite was gone and a sandpapery working edge developed that would still tear through most materials but not scrape shave hair.
The Spyderco definitely held onto the fine edge notably longer and seemed to stay finer over the entire coarse of usage. What was unexpected is the Benchmade feels like it has more toothy particles at the edge when doing the 3-finger test. This lead me to suspect that the softer steel may have a higher carbide volume. When heat treating, the less stabile chromium carbide that is abundant in these steels can be dissolved and is done increasingly as austenizing temperature goes up. Higher autenizing temperatures are generally needed for higher hardness depending on the tempering afterwards. So it is my belief that Spyderco's M390 has less carbide volume overall because it was heat treated at a higher austenizing temperature and tempered at a low enough temperature to hit 61HRc.
The conclusion of the study is that hardness extends the life of the fine edge and the breaking down of the steel remains finer over time until it eventually reaches a similar full working edge as it's lower hardness counterpart. The actual amount of "tooth" or "grit" in the working edge depends on the carbide volume resulting from heat treatment.
Final comment, this test definitely gave me an appreciation for Benchmade's 20CV and renewed my appreciation for working edges. My preference still lies heavily toward the front end, fine edge but a working edge will do just that, work.
Benchmade 940
Steel: CPM-20CV
HRc: 59
Angle: 17
BTE: 0.008"
Spyderco Para 3
Steel: M390
HRc: 61
Angle: 17
BTE: 0.020"
Very interesting. Really love the videos you've done on this topic. This video and the original one you did on PM steel breakdown address one of the main questions I have had up until your videos. Maybe I just didnt catch it or hadn't come across the right stuff but it seems like there was a lot of discussion about edge retention and hardness and such but no one quite illuminated it in this way, particularly regarding your observations on initial high sharpness. Great job!
Michael Cristy talks about it occasionally in some of his videos but never with any depth. I think it’s a very key aspect to steel performance and overall enjoyment! My favorites are easily K390/10V at high hardness because they are the whole package. Takes a sticky edge easy, holds the fine edge for a long time and you basically can’t kill the working edge which tends to be like a working edge plus. Meaning just finer overall. Not sure if that’s due mostly to hardness or vanadium carbide volume. From this experience I’m leaving toward the hardness now.
Great video man 👊
Appreciate it!
Just discovered your channel. Your killing it dude.
Thank you for the kind words! Hope you enjoy the content.
I love these videos
Appreciate it!
Very good info and interesting insights. Just wanted to leave this joke here: I think you came up with Benchmade(tm)'s new slogan for their 2022 line: "Our steel isn't garbage" :D :D :D
😂 I’ll have to trademark it before they take it! Appreciate the comment!
Great discussion! After some time has gone by, what do you think of that particular run of m390 steel? Is it still one of the better options for a para 3 or do you think newer S45vn or something else is better for upfront edge fine holding?
This M390 and similar heat treats Spyderco has done on the PM2s and Manixs still sits near the top of the pack for stainless steel along with their S90V.
I will say that magnacut has really impressed me and is a great option that isn't at the same level but really nice for many. I do enjoy the S45VN over S30V and S35VN so far and consider it a real standout Mid-edge retention option. However I am leaning towards Magnacut between the two options. And that M390 or S90V above either of those.
How well does your chosera work with m390(and its analogs) for you? I've tried to sharpen 10v on mine way back, and it just slid around like glass.
I know those two steels are too close to each other, I'm just curious how it went.
It depends substantially on the hardness, carbide type and carbide volume. They both have similar car due volume but because M390 is largely M7C3 vanadium enriched chromium carbides that are softer than alumina the choseras are an acceptable abrasive IMO.
The speed and feel are very dependent on the hardness so even though the knives in the videos have the same chemistry, the softer BM has sole feedback and totally workable cutting speed. Still ~20vol% carbide so not great either though! The Para 3 however is GLASSY as all get out and the cutting speed is approaching painful for me. Takes a lot of strokes on the 800 to raise a burr.
Compared to 10V that is usually around 65HRc with ~17vol% vanadium carbide the choseras are a total no go. Can’t even feel the stone cutting the steel and the alumina is too soft to shape the vanadium carbide.
I actually have a video on these stones discussing this type of stuff and wrote a report on it for cleaner data sharing. Check it out!
Sometimes I see carbides on my edge on d2 steel . They said d2 has some big carbides . They look like little teeth and it’s not a burr 👍👍. Still cuts very well . I’ve never experienced big carbides with a powdered steel so I’m all for powdered steels nowadays .
My very first knife was a griptillian in D2 and it was honestly amazing. Still a good to go steel but yeah the powder version and all PM steels have a leg up.
S90V is one of my favorite steels.
Benchmades s90v and Spydercos s90v are pretty much on par in my experience. I carried a s90v military for a couple years, then replaced that with a s90v Nakamura but I've recently replaced the Nakamura with a Maxace Heron.
I haven't had any s90v HRC tested, but I've used a TON of it. If I had to guess based on use, that stupid Brian Tighe Spyderco was probably the hardest I've used and the military was probably the softest. Those are the only specific examples that stood out during use/sharpening, everything else just worked.
Sincerely appreciate the info! It's surprisingly difficult to solicit good feedback on these things in the FB groups.
I've been tentative about getting some because it doesn't usually come with that wicked high hardness I've been digging for a couple of years. This test definitely sparked an appreciation for the working edge though and I always have a hunger for vanadium carbide so something in S90V is likely up next on the purchase list.
Sorry if I missed it but how are you controlling your angle?
An angle cube on the KME or muscle memory
Love 20cv it holds and edge forever and ever
Definitely will cut and cut and cut!
Is it easy to sharpen? Or hard? In general. Can it be sharpened standing up in the field on your thigh to a sharp edge for the rest the day, OR does it need a table, go back to the work station, or to the back of the truck, tell all the guys to hold on a second? I'm trying to figure out a steel for me. I have Cruwear, 20cv and M4. All CPM. So... Basically if it's pouring rain I bring 20cv, if it's staples and metal cutting, rough, I'll bring M4 or Cruwear. But I'm liking that cruwear and magnacut is strong, doesn't chip, and they can be sharpened in the field, but is M4 and 20cv sharpen able with a budget item on your thigh?
Have you ever looked at microtech ultra techs? Supposedly their m390/20cv/204p is softer around 58-59. It’s an expensive knife and I wanted it to be harder if I’m spending over $300 on one
I’ve used their XHP in the LUDT and I did feel like it performed better than most S30Vs and S35VNs I’ve come across but not enough to truly enjoy
Man I have a question: can m390 be sharpened with a standard stone or is it high vanadium ?
also how is corrosion resistance ?
In short, yes it can be easily sharpened on decent quality traditional abrasives and it is very stainless. That said I prefer a diamond edge on it and lower end stones like the king with struggle hard with a decent heat treated M390.
M390 and it’s analogs are very high in chromium which results in high corrosion resistance but also the preferential formation of Cr carbides over vanadium carbides. This leads to overall higher carbide volume than S30V or K390 (*heat treat dependent). However it has less Vanadium carbides than even S30V and WAY less than K390 because that chromium “soaks” up all the carbon. This results in a steel that is actually very imbalances and inefficient because it derives its edge retention from chromium carbides that reduce the toughness significantly while not adding as much as she retention as vanadium carbides would.
Knife steel needs wrote a good article on this I recommend you check out as well!
@@EngineersPerspective701 I asked this cause I use diamonds but I always like to use my old stones , also I can buy a M390 knife at cheaper price than Magnacut or else...
And here’s me watching this after buying a Manix2 in m390. Probably should have gotten the s30v one or the s110v. The thing is, the only sharpening system I own currently is the Sharpmaker, so I was worried about sharpening the s110v.
Anyway, great video and good content!
No way man I think you did great! I’ve heard of a lot of those M390 manixs performing super well!
@@EngineersPerspective701 Thanks man, appreciate your response!
Do you ever get a guilty feeling and the urge to reduce the collection down to a handful?
Definitely. Often I think about simplifying things and selling a good handful off. Hopefully will one day!
Does that mean a higher austenizing temp would make the cpm 20cv just like the m390
I know it's hard to get cpm to 61 rc but do you think that would affect the testing
Very likely part of it but it also depends how the associated quench and temper is done for any given austenitizing temp. Cooling rate, cryo, etc!
@@EngineersPerspective701 and this is why true damascus still eludes us smh 🤣
This should be done with the same blade, different steel. That would be far more neat I think to see. There was no nuance lol, it was basically a head to head of a 940 and PM2
The models were irrelevant. The point was anecdotally discussing differences in heat treatment between these two knives.
Other samples of the same exact models could completely change the user experience and comparison. So this is very specific to the exact knives in the video.
That said, it’s likely one could safely extrapolated this to the rest of the knives in their respective batches but factory heat treats are certainly limited in consistency
These are all rubbish , I’m polish and I make my own knife steel, The Tatamovich 229 high chromium content mixed with polish sausage skin, it can cut through 4 meter titanium in 20 seconds, Vishka Vishkovski uses my knives to kill dancing bear. I make best knife in world, like betman.