Super high carbon/high vanadium steels.

[bodog]

Ok, I've been doing some reading and have a question.

Please forgive my stumbles, I know this is very elementary to a lot of you guys.

When you use a hypereuctoid steel you can add more carbide formers but the carbides then get displaced into the grain boundaries. Does the same thing happen when you go to super high levels? I was looking at CPM 15V with what, 14% carbon and like 20 something % carbide formers. It seems to me that at that level the steel can get extremely hard yet at any hardness there's so much weakness in the grain boundaries that it'll either crumble at high hardness or will act like silly putty with embedded razor blades at a low hardness.

Based on what I've read so far only so much can be absorbed into the grains while everything else is pushed off into the boundaries leading to a weaker and weaker steel the higher the concentration of carbides in the grain boundaries. Right? The weakness can be mitigated if the dispersion of carbides is uniform and the grain of the steel is kept very small, which is where PM steels are necessary. But at this level isn't the steel basically a strong ceramic at a high cost? If someone had a blade in a machine that cut fiberglass all day I could see it, but why would it be desirable in a regular knife? I've seen that there's been a lot of problems with rex 121 and I don't see that 15V is all that different. What makes 10V any more suitable? Isn't it still pretty weak?

Sorry for these stupid questions, I'm like a baby trying to crawl with some of these deeper concepts. Don't judge too harshly.

 

[Alpha Knife Supply]

I've seen that there's been a lot of problems with rex 121 and I don't see that 15V is all that different.

What problems have you seen with Rex 121?

Chuck

 

[Darrin Sanders]

I don't know about 15V or Rex 121 but I know a bit about 10V/A-11. My first test blade was .080" Zapp A-11 from Chuck @ Alpha Knife Supply. I hardened it to HRC-63, ground it to ~.010", & convexed the edge to sharp. I cut some paper, cardboard, etc. & then decided to get a little more aggressive. First I drove it through hard Maple across the grain with no damage. Next I drove it through Osage Orange across the grain with no damage. Then I drove it through an Axis deer tine (approx. 3/4" in diameter) and it had a little shiny spot on the edge. It would still cut but would drag slightly in that area of the blade. It took about 2 minutes to get it right back to its original sharpness.
Long story short, 10V is a LOT tougher than most people think. I have a 10V camp knife in the works right now. It should be ready in a couple of weeks and a couple more weeks to get some test results. Keep an eye out for it in the testing & review section of the forum.

 

[samuraistuart]

Tough questions, no doubt. I feel this thread was inspired by the "tired of super steels" thread. The super high carbide steels have their purpose, for cutting super abrasive material under low force for extended periods. If that's what your knife does, then those steels will work MUCH better than simple 1095. If you are not cutting super abrasive material, then my opinion is that you dont "need" them. But "need" and "want" are two different things! ha ha! (steel nut here). Now I haven't tried this myself, but my gut tells me that under normal use, lets say kitchen duty, the S9billionV steels will not give you better edge retention than, say 52100. Nothing super abrasive in normal kitchen duty. Edge retention will be lost mostly due to coming into contact with hard(er) surfaces than the food being cut. Bone, cutting boards, etc. Take that with a grain of salt, tho! Just my current opinion. The work that it takes in making and finishing a high alloy knife becomes a factor in making the knife as well.

I guess to sum it up, to answer your question, "what makes "XYZ alloy steel" more suitable?"....depends on the abrasiveness of the material being cut. They do serve their purpose. Myself preferring low alloy carbon and tool steels.

 

[bodog]

What problems have you seen with Rex 121?

Chuck

In other forums there are people saying the edge dulls quickly cutting anything with some firmness to it. I cannot cross post links to other forums. I am not speaking from personal experience with the steel. As a matter of fact I was seriously considering buying a test blade made out of either 15V or Rex 121 to do some side by side comparisons myself but I cannot afford it right now.

 

[bodog]

To get back on point, I don't care about comparing steels so much in this thread. I brought up specific steels just so people can see what I'm talking about. I'm trying to find out about how the carbides form, exactly where they sit in the steel, and what objective metallurgy says will happen with so much carbon and alloying elements in the mix. I'm trying to learn, not argue.

 

[Alpha Knife Supply]

In other forums there are people saying the edge dulls quickly cutting anything with some firmness to it.

There has been some really good information posted here in Bladeforums regarding this subject. If you are referring to anything from other forums by Cliff Stamp, I would totally disregard the information. He was throughly discredited here by people with much more knowledge.

I recommend buying knives from reputable knifemakers and do some testing yourself. In my personal tests I've found results that surprised me. Like Darrin, my tests with A11 (Bohler K294) have been illuminating. It is not fragile and makes a good hard use knife. My point is, I learned about A11 from my own testing, not the opinions of others.

Chuck

 

[bodog]

There has been some really good information posted here in Bladeforums regarding this subject. If you are referring to anything from other forums by Cliff Stamp, I would totally disregard the information. He was throughly discredited here by people with much more knowledge.

I recommend buying knives from reputable knifemakers and do some testing yourself. In my personal tests I've found results that surprised me. Like Darrin, my tests with A11 (Bohler K294) have been illuminating. It is not fragile and makes a good hard use knife. My point is, I learned about A11 from my own testing, not the opinions of others.

Chuck

The reports were not from Cliff Stamp. And again, I'm not talking about whether 10V is a good steel or not. I don't know why you guys keep pushing it like I am. I posted some questions about metallurgy and what happens to high carbon/high alloy steels and you're making it about whether 10V is a good steel and if Cliff Stamp is worth listening to. I hesitate to even respond to your statement because it's so far away from what I was talking about. Please refer to my original and subsequent posts. I'm asking about super high carbon/ super high alloy mixes and what happens vs what happens with a simple euctoid steel like 1084 where iron and carbon happily mix with each other with little left over. Please stop trying to make it into something it's not.

 

[bodog]

And yes, some of the source material I've been referring to is posted by Stacy Aphelt or Kevin Cashen here on this forum so please stop making it about some dude I don't know nor care about. If either Stacy Aphelt or Kevin Cashen are not reliable sources please let me know now because I'm trying to figure things out based on what they're saying

 

[DevinT]

I don't see any reason to react to other posts. There are two things that are hard in steels. One is the matrix/martinsite and the other is the carbide. As the carbon and or alloy increase there is an increase in carbide volume and size which is the reason for PM steels. Carbides are harder/much harder than martensite. Steels with more and harder carbides are more wear resistant than steels wothout. Carbide pullout and reduced toughness are the drawbacks of higher alloy steels that have lots of carbide.

Hoss

 

[Alpha Knife Supply]

The reports were not from Cliff Stamp. And again, I'm not talking about whether 10V is a good steel or not. I don't know why you guys keep pushing it like I am. I posted some questions about metallurgy and what happens to high carbon/high alloy steels and you're making it about whether 10V is a good steel and if Cliff Stamp is worth listening to. I hesitate to even respond to your statement because it's so far away from what I was talking about. Please refer to my original and subsequent posts. I'm asking about super high carbon/ super high alloy mixes and what happens vs what happens with a simple euctoid steel like 1084 where iron and carbon happily mix with each other with little left over. Please stop trying to make it into something it's not.

A11 is a "high carbon/ super high alloy mix".

I'm not trying to do anything but relay my experiences and knowledge. I'm sorry if you are offended. You may want to consider changing the tone in your posts. You seem to take offense where none is intended.

Please post links to the threads here in Bladeforums where Stacy and/or Kevin discuss your questions.

Chuck

 

[Darrin Sanders]

In your original post YOU asked about 10V so I related my experience with it. You wont have to worry about me cluttering up any of your threads from now on.

 

[me2]

Part of the issue is the sheer volume of the carbides. Lets say you have a bar of steel with a cross section of 1 square inch. Now, lets say your steel has a carbide volume in the hardened condition of 14% (this is close to S30V, if I remember correctly, if not, just go with it). That means that 0.14 square inches of cross section is a hard carbide. Carbides have a tendency to form in the prior austenite grain boundaries, and that makes things a little worse in terms of strength. However, the PM steels have a pretty good distribution of carbides. Micrographs are pretty easy to find, and you can see the carbides are not always surrounding the grains. However, they can and it causes issues. The issue with the PM steels is they have so much carbide and it is so difficult to dissolve, you can't remove them from the grain boundaries if they do end up there.

1095 can have no carbide if heated high enough. S30V can too, but the temperatures are very high, and if all the carbides are gone, the grain size is off to the races in terms of grain growth. I say S30V can have no carbide, but I'm not sure of that. It might be the temperatures to acheive that are so high they cause the steel to start to burn (oxidize around the grains) or even have incipient melting, which is the beginning of melting of the steel. Suffice it to say, these are conditions to be avoided. Now, I've seen some research that says it can be fixed, but it'd probably be cheaper to just buy more steel, even at the high prices of the PM steels.

 

[bodog]

In your original post YOU asked about 10V so I related my experience with it. You wont have to worry about me cluttering up any of your threads from now on.

No man, dang, it's so easy to get things confused. I wasn't talking to you man. Sorry if you thought I was. Good lord, I guess once again I'll back away slowly. Can't even talk about super high carbon and alloying elements without shit getting messed up.

 

[bodog]

Part of the issue is the sheer volume of the carbides. Lets say you have a bar of steel with a cross section of 1 square inch. Now, lets say your steel has a carbide volume in the hardened condition of 14% (this is close to S30V, if I remember correctly, if not, just go with it). That means that 0.14 square inches of cross section is a hard carbide. Carbides have a tendency to form in the prior austenite grain boundaries, and that makes things a little worse in terms of strength. However, the PM steels have a pretty good distribution of carbides. Micrographs are pretty easy to find, and you can see the carbides are not always surrounding the grains. However, they can and it causes issues. The issue with the PM steels is they have so much carbide and it is so difficult to dissolve, you can't remove them from the grain boundaries if they do end up there.

1095 can have no carbide if heated high enough. S30V can too, but the temperatures are very high, and if all the carbides are gone, the grain size is off to the races in terms of grain growth. I say S30V can have no carbide, but I'm not sure of that. It might be the temperatures to acheive that are so high they cause the steel to start to burn (oxidize around the grains) or even have incipient melting, which is the beginning of melting of the steel. Suffice it to say, these are conditions to be avoided. Now, I've seen some research that says it can be fixed, but it'd probably be cheaper to just buy more steel, even at the high prices of the PM steels.

So the individual grains can basically rust throughout the bar?

And if the carbides dissolve, what purpose do they serve? Is that where the statements are made that vanadium can increase toughness?

Would it be as simple as an inferior austenizing/normalizing process itself that would cause the carbides to surround the grains vs mix up throughout the grains and in the grain boundaries?

 

[nzedge]

You have carbide evenly through the steel. Its through hardened.
Iv got a large knife I made from 10v, like a small kitchen katana type thing. Hardened to 63-64.
Its not really brittle at all. Its brittle compared to some really tough malleable steels, but its still pretty tough..not at all like ceramic.
Iv used my large 10v knife to cut everything from vegetables, to meat, to clean through large think fijian mud crab shells, to things on my car (lol), to opened cans of food...iv even used it as a chopper to chop through lamb leg bones...(didnt have a cleaver)

It sharped it yesterday, had to remove a nick from chopping the lamb leg bone..it took me about an hour with multiple coarse diamond stones..it is however the sharpest most wear resistant thing i have ever seen.

 

[me2]

So the individual grains can basically rust throughout the bar?

And if the carbides dissolve, what purpose do they serve? Is that where the statements are made that vanadium can increase toughness?

Would it be as simple as an inferior austenizing/normalizing process itself that would cause the carbides to surround the grains vs mix up throughout the grains and in the grain boundaries?

Yes, if the temperatures get too high, the steel can be damaged by oxidation around the grain boundaries. When you hear of smiths "burning" steel, this is what is happening. I've not seen it myself, but it has been described as pulling the bar from too hot a forge and having it behave like a sparkler.

For the second answer, it is necessary to understand the annealed steels have much more carbide volume than hardened steels. 1095 for instance has about 15% carbide in the annealed condition, but only about 2%-3% in the hardened condition most commonly used. Since ferrite in annealed steel cannot hold essentially any carbon at all, virtually all if the carbon is present in carbides. In this sense, carbides are useful to hold the carbon for later. When they dissolve, the carbon is free and absorbed into the matrix between the iron atoms. When quenched, the carbon doesn't have time to reform carbides, thus stays and forms the martensite we all know and love. What I mean in a way is we don't get to decide if the carbides are there to serve a purpose. They are there and we just have to find a way to make use of them. Dissolving carbides are the first step in the secondary hardening seen in many complex alloys, and even in 1095 under the proper circumstances.

Statements about vanadium increasing toughness are generally geared toward the use of vanadium and vanadium carbides to pin grain boundaries and prevent grain growth and loss of toughness that comes from it, at least all the ones I've seen mentioned.

In simpler steels, an inferior annealing process usually results in the surrounding of the grains with carbide (see below). In more complex steels, I'm not sure what would happen. A botched annealing process in them usually means they just hardened when softening was the intent. I'm not sure how an inferior austenizing could result in a lot of grain boundary carbides, but I'm sure it's possible if you mess it up enough. An inferior normalizing can lead to all sorts of issues, especially if the textbook version of "normalizing" is used. Most complex steels, A2 and up, warn against normalizing, as some A2 data sheets I've seen specifically say "do not normalize." If the knife making version of normalize is used (heat to austenizing and air cool), then a different set of issues may be the result. In complex, high alloy steels, those instructions are basically hardening instructions, not normalizing.

 

[bodog]

Awesome response man, thank you.

If you have 15% (or 20 or 30% or any number) carbide volume in the annealed state and all of the carbides dissolve during hardening, would the steel basically act like a properly hardened euctetic steel at the same hardness?

 

[james terrio]

You're making a lot of assumptions, and they really don't take into account what actually seems to happen when high-carbide-forming alloys are heated up and go into "solution". Ever try to bake a cake with a block of wheat flour and a chunk of sugar? Of course not... they wouldn't mix and react worth a hoot. That's a hugely extreme example, but it really is sort of like that when it comes to making high-alloy steels.

Yeah, if you just slammed 12-15% chrome and 1 or 3% vanadium into a typical crucible steel, that would be a chunky mess. You'd end up with something like 440C or D2... which aren't "bad" alloys at all, but they're not as good as they could be, either.

You have to keep in mind that modern "powder" steels with that kind of alloy content are designed, and manufactured, specifically to avoid those big "clumps" of carbides and the interstitial/boundary stuff that causes the kinds of weakness you're worried about.

Never mind datasheets and theories and microscopes; make you a couple blades out of 154CM and CPM-154 and compare them. The differences in their structure and properties will very quickly become clear, even though the chemistry is nearly the same.

 

[me2]

Awesome response man, thank you.

If you have 15% (or 20 or 30% or any number) carbide volume in the annealed state and all of the carbides dissolve during hardening, would the steel basically act like a properly hardened euctetic steel at the same hardness?

At first glance, that might appear to be the case. However, even in 1095, dissolving all the carbides is not desirable. First, it puts too much carbon into the austenite and, upon quenching, the hardness will start going down. This decrease in hardness is due to an increase in retained austenite. Second, those undissolved carbides provide the wear resistance these complex alloys are known for. Third, dissolving those carbides and putting carbon into the austenite also means putting the other elements into the austenite, such as chromium, vanadium, etc. These will typically increase the amount of retained austenite as well. Third, these complex alloys require high temperatures to harden. The carbides act as speed bumps to slow down grain growth. If they were all gone, the grains would grow very large very quickly. Now, some carbides have to dissolve. The trick is how much and at what temperature. It's a balancing act; just enough, but not too much.