Hi Larrin. I'd love to see a video about DLC coating and Rockwell hardness. I have a hard time wrapping my mind around how applying a very thin coating of something harder than the blade steel, actually reduces HRC. It's kind of counter intuitive, and I think a video on it might be very interesting.
When the coating is applied it has to be "baked" on to the steel and if that temperature is higher than the original tempering temperature the hardness of the steel is reduced. In other words, applying the coating means the steel is tempered hotter. The coating is not on the edge so there is a potential reduction in strength and cutting performance at the edge.
@@KnifeSteelNerds A video on this would be super interesting. The influence of the coating on the corrosion resistance is also hard to understand, because the VPD coating are *in theory* so thin that they allow corrosion to build underneath. In reality you can rarely get all the important info from the manufacturing process, because a lot of companies outsource both the coating and the HT. Speaking about HT processes with marketing department of knife companies fails with 100% reliability.
Thank you Dr. Thomas, l am a knife maker in Taiwan and got a lot of help from your articles. May l ask a question? I am curious about that will there be some difference in wear resistance between tempered martensite and bainite(especially for Carbon steel)? Because there will be rare or very small size carbides after carbon steel got quenched, but in bainite carbides form completely.
Carbides are also found throughout tempered martensite. That is what happens during tempering is that carbon goes out of solution as small temper carbides. There are some studies that have shown a small advantage for bainite vs tempered martensite at the same hardness. This is due to either more carbide, larger carbides, or retained austenite. Retained austenite is undesirable for knives, and the type of wear resistance tests that show an advantage from that are when high pressure leads to retained austenite being converted to untempered martensite, which we don't want. Furthermore, selecting a steel with higher carbide volume would lead to a much greater difference than a tiny difference in carbide volume of tempered martensite vs bainite. I have a discussion of this subject and references at the end of this old article: knifesteelnerds.com/2018/07/09/bainite-vs-martensite/
I would really love to see the tables for both 8670M and 15n20 steels for sword blades, and how this relates to spring tempering. Fantastic video, thank you.
You could compare the 1095 result (24:00) to a hitachi white paper #2, or Takefu V2c (V2 has a touch more nickle and Cr), which should both have tighter control of P and S impurities than 1095.
Yeah, I would be interested in maybe seeing a 1095 second source tested, because it's evident at this point from the 26c3 and this bainite test that his sample isn't as tough as it could be. Though, it is totally fair if it's from one of the big knife supplies as for being real world practical. Though I wonder how much 1084 would vary, as well. 1095 from uddeholm would likely be better faring. The steel source that Mora uses is quite tough in practice, and comparing to their 12c27 evidently not 4x as bad toughness.
I never thought I'd pop a chub during a lecture on bainite formation in knife steels, but then again, when you start talking about tough, resilient structures under pressure, it's hard not to feel a little heat treat in the air! 😂
Extremely interesting. I will definitely utilize this as I don't need the absurd hardness of 60+. I wonder what would happen if you did indeed austemper something like high speed steel for 48hrs lol.
It's reasonably popular (comparably) for sword making, where at 55 and under, the bainite is much tougher in high carbon steels. I could see bainite Wootz being very interesting, since it's got very high carbon.
minutes, seconds and hrc, ok. but Fahrenheit? i have learned english in school but the temperature unit is like listening to greek 😂 very interesting information. Thanks for sharing.
Makes me wonder how much tougher zdp could be in tempered this way, whilst keeping the insanely high hrc. I've never really understood bainite processing, this video helps me make some sense of it, but it also gives me the impression that my favourite steel, zdp, would have to be held for days to get toughness up to small load batoning levels
I'm obsessed with firing pins, where the hardness isn't even very high and is close to 48 rockwell. I read that 1095 and 5140 create bainite in just a few minutes. I lost three firing pins, always firing, never during dry fire.
Nice clip. There are metalrecipes with tin and bismut that go around 400°C you can long quench then the steel in a metalbath. Looks fancy too 😅 Just never drop a blade or whatsoever with oil or grease on into such a high temp liquid or it will EXPLODE into your face. Why? Because the stuff will like to evaporate in the 400°C bath. The blades are very tuff indeed, we made some a few years ago.
Great video. I have a beautiful knife from a M.S. known for his salt pot quenching. It may be tough (don't know) but it won't hold an edge. It is not really usable as a hunting knife. Marquenching is very geeky and clever, but why would any knifemaker -want- a knife with less edge holding? No more chopping bamboo and chopping rope ... give us knives that stay sharp.
Trying to bend a bainitic lawnmower blade back into shape blew me away, and theyre usually nearly mild steel. Id love to try a high carbon bainite knife
Hello Larrin, amazing video/study as usual. I'll definitely read the article too. I most likely didn't understand everything and will need to read the article, but from this study, should I be able to understand how Howard Clark achieved bainite on the spine and martensite on the edge for its L6 sword?
I believe the rumor is that Howard does an austemper on the entire blade and then heats the edge with a torch and quenches in oil. If Howard has given more specific details somewhere hopefully someone can post a link. I believe his bainite spine is somewhat lower in hardness than what I was trying to achieve here.
@@KnifeSteelNerds Thanks a lot for replying. Many years ago, like a dozen or even more, I read on a forum that he had never given details about his process and said something like: " I didn't invent anything, the information is out there, find it out for yourself ". Not literally from Howard Clark himself, just what I remember. In other words, he wasn't going to reveal his process, but he was humble and said there is really nothing "magical" about it. Maybe he has finally revealed his process after that though...
Most oils have a flash point that is too low, there are marquenching oils that can be used for lower austempering temperatures. I don’t know where to buy them though.
Hay what happens when you have a really strong magnate surounding a quenching bin, while the steel cools down it would regain its magnetic pull, would that mess things up or could you control processes during the quenching if you diled it in a really well? I know nothing about metalergy, but i always wonder if anything wh change about it, could you align grains or eliminate gaps in the steel
Intuitively you'd get oriented crystal structure. What that would do to strength I wouldn't know, but could be anisotropic strength. Could be a PhD thesis in testing this.
I found some discussion online of Narex austempering but they don’t seem to claim it anywhere on their website. The 59 Rc claimed for many of the chisels could feasibly be achieved with austempering though.
@@KnifeSteelNerds as I recall I heard about it from some behind the scenes manufacturing videos they produced for marketing purposes. not sure if those are still online anywhere
OK, so, having now watched this and the other salt pot video, I am led to wonder... what happens if you pull the steel from the hotter salt, and then quench it in the cooler but still really darn hot salt in the *other* pot, for the x3 cycle? Might that solve the martensitic plate formation problem? Also, if one is going to do this, is there a point at which you'd still want to cryo the steel?
Increasing toughness using martempering will also increase other strenghts like shear strenght and shear modulus? Whats the common property to specify the toughness of a steel? The UTS or something else?
Those two steels are very different but probably with both I would say no. I would prefer to take the 60-61 Rc and very high toughness with Q&T of 15N20. And 154CM being a high alloy stainless wouldn’t be a good pick for austempering.
@@Popeii1 it's very rust proof, but it's not incredibly wear resistant, so it makes sense to me, if you like the look of DMT, that you can put it on magnacut no problem. Unless we're talking about a high carbon steel that rusts easily, DMT is an aesthetic choice mostly, in my opinion.
@Ingeb91 Some people like chocolate, some people like vanilla.I hate coated blades. It's a matter of taste, and you can't argue about somebody's taste.
@@KnifeSteelNerds Oops! I only can Celsius. So Bainite forms in 400 F? My fault. However, low temperature metal alloys like Woods metal might be suitable though. Does the high heat transfer have a negative impact on forming Bainite?
I've been trying to "tell" of this for years, thanks for highlighting!
Anyone who understands metallurgy will be using an alloy like AEB-L for twice the toughness O1 Bainite.
@@rockets4kids
Twice the toughness of Bainite O1? That much?
I love AEB-L anyhow, definitely an underrated and under used steel.
It is kind of insane how many variables there are in steel metallurgy. A video on marquenching+cryo next? heh...
Thank you for another awesome video!
Hi Larrin. I'd love to see a video about DLC coating and Rockwell hardness. I have a hard time wrapping my mind around how applying a very thin coating of something harder than the blade steel, actually reduces HRC. It's kind of counter intuitive, and I think a video on it might be very interesting.
When the coating is applied it has to be "baked" on to the steel and if that temperature is higher than the original tempering temperature the hardness of the steel is reduced. In other words, applying the coating means the steel is tempered hotter. The coating is not on the edge so there is a potential reduction in strength and cutting performance at the edge.
@@KnifeSteelNerds A video on this would be super interesting. The influence of the coating on the corrosion resistance is also hard to understand, because the VPD coating are *in theory* so thin that they allow corrosion to build underneath. In reality you can rarely get all the important info from the manufacturing process, because a lot of companies outsource both the coating and the HT. Speaking about HT processes with marketing department of knife companies fails with 100% reliability.
Thank you Dr. Thomas, l am a knife maker in Taiwan and got a lot of help from your articles.
May l ask a question? I am curious about that will there be some difference in wear resistance between tempered martensite and bainite(especially for Carbon steel)? Because there will be rare or very small size carbides after carbon steel got quenched, but in bainite carbides form completely.
Carbides are also found throughout tempered martensite. That is what happens during tempering is that carbon goes out of solution as small temper carbides. There are some studies that have shown a small advantage for bainite vs tempered martensite at the same hardness. This is due to either more carbide, larger carbides, or retained austenite. Retained austenite is undesirable for knives, and the type of wear resistance tests that show an advantage from that are when high pressure leads to retained austenite being converted to untempered martensite, which we don't want. Furthermore, selecting a steel with higher carbide volume would lead to a much greater difference than a tiny difference in carbide volume of tempered martensite vs bainite. I have a discussion of this subject and references at the end of this old article: knifesteelnerds.com/2018/07/09/bainite-vs-martensite/
@@KnifeSteelNerds Thank you!
I would really love to see the tables for both 8670M and 15n20 steels for sword blades, and how this relates to spring tempering. Fantastic video, thank you.
Whoah super toughness!!!
I want that!
Was looking for this info for a long time. Thank you ;
Phenomenal video.... wow! Brilliant work!
Another great video Larin, thank you very much as always!
You do great work Larrin
An excellent discussion, thank you, Larrin! Very interesting.
You could compare the 1095 result (24:00) to a hitachi white paper #2, or Takefu V2c (V2 has a touch more nickle and Cr), which should both have tighter control of P and S impurities than 1095.
Yeah, I would be interested in maybe seeing a 1095 second source tested, because it's evident at this point from the 26c3 and this bainite test that his sample isn't as tough as it could be. Though, it is totally fair if it's from one of the big knife supplies as for being real world practical. Though I wonder how much 1084 would vary, as well. 1095 from uddeholm would likely be better faring. The steel source that Mora uses is quite tough in practice, and comparing to their 12c27 evidently not 4x as bad toughness.
Very interesting. Thank you.
I never thought I'd pop a chub during a lecture on bainite formation in knife steels, but then again, when you start talking about tough, resilient structures under pressure, it's hard not to feel a little heat treat in the air! 😂
Extremely interesting. I will definitely utilize this as I don't need the absurd hardness of 60+. I wonder what would happen if you did indeed austemper something like high speed steel for 48hrs lol.
It's reasonably popular (comparably) for sword making, where at 55 and under, the bainite is much tougher in high carbon steels. I could see bainite Wootz being very interesting, since it's got very high carbon.
minutes, seconds and hrc, ok. but Fahrenheit? i have learned english in school but the temperature unit is like listening to greek 😂 very interesting information. Thanks for sharing.
Makes me wonder how much tougher zdp could be in tempered this way, whilst keeping the insanely high hrc.
I've never really understood bainite processing, this video helps me make some sense of it, but it also gives me the impression that my favourite steel, zdp, would have to be held for days to get toughness up to small load batoning levels
The high hardness of the ZDP-189 would not be maintained with austempering.
I'm obsessed with firing pins, where the hardness isn't even very high and is close to 48 rockwell. I read that 1095 and 5140 create bainite in just a few minutes. I lost three firing pins, always firing, never during dry fire.
Nice clip. There are metalrecipes with tin and bismut that go around 400°C you can long quench then the steel in a metalbath. Looks fancy too 😅
Just never drop a blade or whatsoever with oil or grease on into such a high temp liquid or it will EXPLODE into your face. Why? Because the stuff will like to evaporate in the 400°C bath.
The blades are very tuff indeed, we made some a few years ago.
loved it
Great video. I have a beautiful knife from a M.S. known for his salt pot quenching. It may be tough (don't know) but it won't hold an edge. It is not really usable as a hunting knife. Marquenching is very geeky and clever, but why would any knifemaker -want- a knife with less edge holding?
No more chopping bamboo and chopping rope ... give us knives that stay sharp.
Trying to bend a bainitic lawnmower blade back into shape blew me away, and theyre usually nearly mild steel. Id love to try a high carbon bainite knife
Hello Larrin,
amazing video/study as usual. I'll definitely read the article too.
I most likely didn't understand everything and will need to read the article, but from this study, should I be able to understand how Howard Clark achieved bainite on the spine and martensite on the edge for its L6 sword?
I believe the rumor is that Howard does an austemper on the entire blade and then heats the edge with a torch and quenches in oil. If Howard has given more specific details somewhere hopefully someone can post a link. I believe his bainite spine is somewhat lower in hardness than what I was trying to achieve here.
@@KnifeSteelNerds
Thanks a lot for replying.
Many years ago, like a dozen or even more, I read on a forum that he had never given details about his process and said something like: " I didn't invent anything, the information is out there, find it out for yourself ".
Not literally from Howard Clark himself, just what I remember.
In other words, he wasn't going to reveal his process, but he was humble and said there is really nothing "magical" about it.
Maybe he has finally revealed his process after that though...
I have worked with C130/ C125U that is 1.3%C carbon steel, I'm sure the toughness difference at 61hrc would be huge
Is there any necessity to heat treatment high alloy steels like M2 in vacuum?
Thank you! Excellent info. So, would this be a good choice for a JS performance knife?
Potentially, though “differential hardening” is typically more effective. I think someone in the comments said they passed with a bainite knife.
Austemper can be made in heated oil? Or any other liquid or inside a oven?
Most oils have a flash point that is too low, there are marquenching oils that can be used for lower austempering temperatures. I don’t know where to buy them though.
Hay what happens when you have a really strong magnate surounding a quenching bin, while the steel cools down it would regain its magnetic pull, would that mess things up or could you control processes during the quenching if you diled it in a really well? I know nothing about metalergy, but i always wonder if anything wh change about it, could you align grains or eliminate gaps in the steel
Intuitively you'd get oriented crystal structure. What that would do to strength I wouldn't know, but could be anisotropic strength. Could be a PhD thesis in testing this.
A magnet wouldn’t change martensite or bainite formation
www.jstage.jst.go.jp/article/matertrans/48/11/48_MI200718/_article/-char/ja/
@@KnifeSteelNerds the linked article says there is an effect.
It says that Bs and Ms can be shifted but that the morphology of the structure doesn’t change for martensite or bainite.
narex claims to austemper some (all?) of their woodworking tools and they've had great edge retention at low bevel angles for me
I found some discussion online of Narex austempering but they don’t seem to claim it anywhere on their website. The 59 Rc claimed for many of the chisels could feasibly be achieved with austempering though.
@@KnifeSteelNerds as I recall I heard about it from some behind the scenes manufacturing videos they produced for marketing purposes. not sure if those are still online anywhere
OK, so, having now watched this and the other salt pot video, I am led to wonder... what happens if you pull the steel from the hotter salt, and then quench it in the cooler but still really darn hot salt in the *other* pot, for the x3 cycle? Might that solve the martensitic plate formation problem?
Also, if one is going to do this, is there a point at which you'd still want to cryo the steel?
Two pots can be used, yes. Whether you use cryo is a separate question.
Yes, but what does it mean for MagnaCut?
Thank you for a great video. Would 80CRV2 be a good candidate for austempering?
Potentially, though the hardness would be even more limited than these 1% carbon steels I tested.
Increasing toughness using martempering will also increase other strenghts like shear strenght and shear modulus? Whats the common property to specify the toughness of a steel? The UTS or something else?
Toughness is tested with impact testing. UTS and other measurements of strength correlate with hardness not toughness.
So, in your opinion, would austempering 15N20 or 154CM produce a better balance of characteristics?
Those two steels are very different but probably with both I would say no. I would prefer to take the 60-61 Rc and very high toughness with Q&T of 15N20. And 154CM being a high alloy stainless wouldn’t be a good pick for austempering.
Why are people coating some MagnaCut blades?
There are coatings that are harder than 60 something hrc, so I would guess it's to protect against scratches
@Ingeb91 This seems to me the steel that should be polished like Rockstead knives.
@@Popeii1 it's very rust proof, but it's not incredibly wear resistant, so it makes sense to me, if you like the look of DMT, that you can put it on magnacut no problem. Unless we're talking about a high carbon steel that rusts easily, DMT is an aesthetic choice mostly, in my opinion.
@Ingeb91 Some people like chocolate, some people like vanilla.I hate coated blades. It's a matter of taste, and you can't argue about somebody's taste.
@@Ingeb91 i meant to say thank you for the information
SWEET‼️I really like O1, ~60HRC, for bushcraft knives... The Bainite way will give irt very good toughness too (ICING ON THE CAKE😎)
Can I austemper in molten tin at 400 deg.?
Tin melts at 450F
@@KnifeSteelNerds Oops! I only can Celsius. So Bainite forms in 400 F? My fault.
However, low temperature metal alloys like Woods metal might be suitable though. Does the high heat transfer have a negative impact on forming Bainite?
👍✌️⚒️
would W2 or 8670 be good steels to austemper for larger blades or swords?