What are the advantages and disadvantage of 100% Bainitic knives?

[cotdt]

Some steels like 52100 can reach ~60 rc as 100% bainite, which satisfies the requirement of a good cutting knife. I know bainite swords have been made, but has anyone ever tested a bainite knife? What are the pros and cons compared to tempered martensite?

 

[wnease]

i've tried knife blades from 8670m banite @ rc57...not great edge holding, but not crap, found i could get the edges pretty thin without chipping, but i'd like to know more too

 

[cotdt]

i've tried knife blades from 8670m banite @ rc57...not great edge holding, but not crap, found i could get the edges pretty thin without chipping, but i'd like to know more too

Very interesting. Did you try any bending tests? What was your heat treat procedure for 8670M bainite?

 

[Kevin R. Cashen]

Some steels like 52100 can reach ~60 rc as 100% bainite, which satisfies the requirement of a good cutting knife. I know bainite swords have been made, but has anyone ever tested a bainite knife? What are the pros and cons compared to tempered martensite?

cotdt, could you share the source of the 60rc bainite information? I am very interested in reading more about the topic.

 

[cotdt]

cotdt, could you share the source of the 60rc bainite information? I am very interested in reading more about the topic.

I read about it in Verhoeven's ebook "Metallurgy of Steel", pg 119. He obtained 60 rc 100% bainite 52100 with 1550F austenization and held at 475F. Measured 50 lb-ft on unnotched izod impact. However, there was no mention of cutting performance.

 

[Kevin R. Cashen]

O.K., I had figured it was Verhoeven but when you mentioned other steels I had hoped you had found more sources. You may try looking up some of Bhadeshia's work, the guy know as much about Bainite as Edgar Bain himself.

 

[Gabe Newell]

The best part about bainite is that it makes Kevin's head explode, especially if it is triple-quenched in goop.

The worst part about bainite is that the trade-off between hardness and toughness is usually non-optimal for real world knives.

But then one of my projects for the year is to try to austemper M4, so I'm lunatic fringe and can be safely ignored.

 

[mete]

We had discussed that subject in absolute detail and concluded it wasn't worth playing with. Yes it hurts Kevin's head !! As for tool steels there was one TTT diagram the showed that the bainite transition STARTED after 20 hours !!! Always check the TTT first !

 

[Gabe Newell]

Hey, Mete.

Some researchers in India were updating the M4 chart (I think they had a more precise dilatometer but I don't have the paper on front of me) and it was 4 hours. I'll post whatever I find out.

 

[Stacy E. Apelt - Bladesmith]

For those who don't know what the fuss is about;
When steel cools down from being austenitized ( at around 1500F) we usually say it has two ways to go - soft pearlite or hard martensite. The doorway is called the pearlite nose, at 1000F. If you pass the nose in the time shown on a TTT chart, you will get martensite, too slow and you get pearlite. However, there is a third structure that is possible with some knife grade steels - Bainite. Bainite forms when you pass the pearlite nose, but don't reach the martensitic start point (around 400F). By holding the blade at some point around 450-475F, the steel forms the bainitic structure. Bainite is tough. The biggest reason we don't hear about it is it takes from ten to thirty hours for it to form. That requires a special equipment.

Before one thinks, "TOUGHER, yeah I want that!", remember that hard rubber is many times tougher than steel, but it doesn't cut worth crap. Bainite can be made into a blade, and some sword makers make bainite swords. About the only plus is a very tough blade that will take impact well and bend. Some of the minus are that bainite will not take as good and edge,the edge won't hold up to use, the cost of a fifteen+ hour burn, and the need for specialized salt pots ( Standard knife kilns and salt pots are not meant to run for those time periods).

Since most knife makers want a sharp knife, and bending is not normally a desirable feature in most knives, there is no real reason to make a bainitic knife. For 99.9% of all knife uses, martensite is the ticket to a good knife. Learning to master the HT to attain a 100% martensitic blade at the target hardness is enough of a challenge for most makers.

I am sure some will say, "But I read about the super bainite swords, made by XXXXX". Yes there is a commercial maker of bainite swords....and when was the last time swords were used in actual sword use? I would be willing to bet that if people needed swords for offensive/defensive reasons, you would see no bainite swords on battlefields. The closest to those conditions comes in modern cutting practice and competitions ( tameshigiri). I don't follow these much, but would think if there was an advantage, the bainite swords would stand out. It is my thoughts that the things that go along with bainite will make the sword a poor cutter. Again, before anyone jumps up and says, " but sensei XXX cut through a 12" rolled tatami with a bainite sword.",that there are those with skill enough to cut with almost anything. One famous samurai was known for throwing his sword on the ground and fighting with the saya, because he did not need a sword to dispatch many of his less skilled opponents.

I did some experiments on trying to attain a martensitic edge with a bainitic spine. Without lab testing, there was no way to really know what I actually got, but the results were not better ( actually a lot worse) than a standard differentially hardened blade.
When I discussed this idea with Kevin, his head spun around....everyone ran from the room....and he replied " You should do that, and let me know how it works out for you." ( just kidding ,Kevin)

I have been told that some ABS tests were done with bainite knives, but IIRC, only one was successful.

If you wanted a tough blade that would bend, make it out of titanium. It would be about the same as a bainite blade without all the trouble.You can sharpen it to a fair edge, but it won't last long in use.


Stacy

 

[jdm61]

I have been reading a bit about japanese style blades of late because I am trying my hand at making some. The consensus among the people who frequent the sword sites seems to be that the well know custom bainite swords are tougher than nails but do not have the edge retention of comparable martensite/pearlite swords. I also got the impression that those swords were differentially hardened because they still have a hamon, albeit a faint one compared to that which you see on a standard martensistic sword made from shallow hardening steel.
As for the commercial versions, they seemed to be claiming that they make a sword with a martensitic edge and bainite body. I may be wrong.

 

[Kevin R. Cashen]

Now that my convulsions have subsided to just occasional spasms, perhaps I can elaborate. Edgar Bain’s love child hybrid of pearlite and martensite does not actually drive me into a frenzy at any time other than the full moon, and then it is nothing that a little holy water won’t fix.

But seriously, I love bainite, that is why I got excited at the prospect of there being some new research or literature about it. I love studying virtually every phase and microstructure in steel, it is my passion. I also love pearlite (the most beautiful under the microscope), ferrite (striking in decarbed steel), and huge carbide networks. They are all too cool not to study at every opportunity! I just prefer not to have them in my knives. I would also much rather read “Principles of Heat Treatment” by E.C. Bain than the March issue of “Kung Fu Ninja Secrets.” My friends enjoy prodding me with a lower bainite stick due to my apathy on knives made from it

I once showed a friend a bainitic fork I had made, and he just frowned and asked, “what’s the point?”, with a grin I replied “exactly!”

 

[sunshadow]

I have been reading a bit about japanese style blades of late because I am trying my hand at making some. The consensus among the people who frequent the sword sites seems to be that the well know custom bainite swords are tougher than nails but do not have the edge retention of comparable martensite/pearlite swords. I also got the impression that those swords were differentially hardened because they still have a hamon, albeit a faint one compared to that which you see on a standard martensistic sword made from shallow hardening steel.
As for the commercial versions, they seemed to be claiming that they make a sword with a martensitic edge and bainite body. I may be wrong.

CAS Hanwei is indeed claiming to have a martensite edge and bainite body in an L6 blade. I don't imagine that they sell too many $1700 swords for actual use

-Page

 

[Stacy E. Apelt - Bladesmith]

My experiments on attaining a martensitic edge and a bainitic body and get a hamon was this:
I started with an ABS JS test style blade and no clay coating. Blade was 3/16" 1095. I austenitized the blade at 1475F, and after a soak, quenched it into 425F salts. I let it stay there for about 30 seconds to allow equalization, then pulled the blade and edge quenched in flowing room temperature brine solution. The brine was pumped across a sheet of steel, so it ran about 1/8" deep. The edge was rapidly rocked along the entire cutting area for about ten seconds, quickly wiped off and plunged back into the salt pot for 4 hours. The theory was to drop the austenite to the brink of the Ms; quench the edge into martensite; and austemper the still austentitic body into bainite. The results indicated a quite soft Rc 46 body, and a hard edge ( no way to measure, but I guessed it to be Rc58 area. There was a slight hamon, as with any edge quenched blade.The edge was a bit chippy, so I re-tempered at 450F. That helped a bit, but overall performance and sharpness was mediocre at best. Although I didn't do any heavy cutting with it, I don't think it would have passed the chopping/cutting test and remained hair shaving sharp. On bending ,the edge cracked, but the spine just took a set. That part of the test went well, but it would have done the same if the spine was pearlite and the edge martensite ( which would have only required a clay coated blade, and drawing the spine with a torch).

The end results were that it was surely possible....but WHY ?

Stacy

 

[cotdt]

This is a very enlightening thread. Bainite forks sound like a great idea. You can stab it into a big ham, and pick up the entire ham with the fork without damage to the fork.

What about a bainite 10" chopper as a camp knife, through-hardened? Edge retention won't be important. It will be hard enough to avoid edge rolling and very tough. Is this worth trying or would I be wasting my time?

Stacy, was your 1095 bainite at least very tough? Is it as tough as the shock steels?

 

[Yang Tomoe]

Now that my convulsions have subsided to just occasional spasms, perhaps I can elaborate. Edgar Bain’s love child hybrid of pearlite and martensite does not actually drive me into a frenzy at any time other than the full moon, and then it is nothing that a little holy water won’t fix.

But seriously, I love bainite, that is why I got excited at the prospect of there being some new research or literature about it. I love studying virtually every phase and microstructure in steel, it is my passion. I also love pearlite (the most beautiful under the microscope), ferrite (striking in decarbed steel), and huge carbide networks. They are all too cool not to study at every opportunity! I just prefer not to have them in my knives. I would also much rather read “Principles of Heat Treatment” by E.C. Bain than the March issue of “Kung Fu Ninja Secrets.” My friends enjoy prodding me with a lower bainite stick due to my apathy on knives made from it

I once showed a friend a bainitic fork I had made, and he just frowned and asked, “what’s the point?”, with a grin I replied “exactly!”

I am Glad that I found a Banite enthusiast.

What do you think of using Banite for throwing knives? A throwing knife does not need to keep a razor sharp edge yet needs to be shock resistant. Toughness and strength seem more important than having a super hard edge. Is banite hard enough to prevent deformation of the edge on impact with a target? What kind of edge deformation can we expect from impact on bone, concrete, wood etc. Will a banite throwing knife resist breakage better than pearlite. Will it resist taking a bend like martensite? Will it shatter!?! I don't know! Do you?

I mean it's one thing to hold onto a knife and baton it into a copper pipe, and another to huck a knife at plywood or bone. Even with a straight throw the forces involved are fairly different.

Last but not least, the cost. Is it more expensive to make a throwing knife out of banite steel, or to get them made from something exotic like titanium?

Thanks.

 

[weo]

Good morning, Yang, welcome to the forum.

I am Glad that I found a Banite enthusiast...

Allow me to suggest that you check out when a thread had its last response before re-opening and asking a question. This thread was started over 10 years ago, and it looks like it's been over 6 months since cotdt last logged on to this site.

 

[Yang Tomoe]

Good morning, Yang, welcome to the forum.


Allow me to suggest that you check out when a thread had its last response before re-opening and asking a question. This thread was started over 10 years ago, and it looks like it's been over 6 months since cotdt last logged on to this site.

Ah yes i see that Kevin last logged on back in 2016....drat. Thanks for the heads up.

 

[Natlek]

SKF /ball bearing manufacturer/ claim that they have new steel capable for 60 hrc bainite ..
755V steel

The hardness of the new bainitic steel is at least as high as that obtained with martensite heat treatment or case hardening. This has been obtained without the loss of toughness, crack resistance and structural strength that characterise bainite steel. Wear tests have shown that wear resistance is more than twice that obtained with standard bainite structures.