154CM performance discrepancies (datasheets vs. 'real-world')

[doggyknife]

I've been looking over some of Crucible's steel data sheets comparing 154CM and various other steels, and something 'odd' keeps coming up. On the data sheets, 154CM always seems to be rated higher in wear-resistance, corrosion resistance, and toughness than 440C.

My original impression of 154CM (mainly from the experiences and postings of other knife users) was that while it had better wear-resistance than 440C, it had LESS corrosion resistance and LESS toughness than 440C. My own experiences with 154CM and ATS-34 tell me that 154CM holds an edge a little better than 440C, but I haven't really noticed any difference in corrosion resistance or toughness between the 2 steels.

Now I know that how the steel is heat treated (among other processes and aspects) can make all the difference in the world on how a knife steel performs. But judging from the differences between the datasheets and what is generally accepted as 'truth' around here, does this mean that no production companies or custom makers have been heat treating 154CM correctly (i.e. according to Crucible's specs)? Have companies and makers been altering the 'ideal' heat treat to get more edge-holding at the expense of corrosion resistance and toughness?

I'm no metallurgist or knifemaker, so any insight into this discrepancy would be appreciated.

 

[Jerry Hossom]

You need to be a little careful using that data, because significant qualifiers are scattered around on different pages. None of the data you've seen is specific to knife blades, being more generally applicable to larger cross-sections than knife blades and in uses like extrusion screws, etc, that are usually unrelated to anything we care about. The hardness used in the testing is not constant either, nor always at knife blade levels.

Heat treating of knife blades is seldom done at the temps and conditions recommended in Crubible's book, and frequently uses methods that are specific for knife blades. Crucible's data usually does not include cryogenics, which dramatically alters the results for each steel, as does the quench rate which is an important but seldom mentioned variable.

I guess what I'm saying is that the variables are far more varied than is discussed in the books, and are usually specific only for the tool or part being produced or for which the tool was designed. (Edit: Oops, I meant to say, "and for which the steel was designed." Sorry)

 

[doggyknife]

Thanks for clearing some of this up, Jerry.
I knew there was a bunch of aspects I wasn't considering in 154CM application to knives specifically.

 

[Cliff Stamp]

Regarding CPM, I would obviously not consider them (or anyone else) an unbiased source of information on the products that they sell. However, the biggest problem with them is that they don't give very consistent information. In the "orange book" from CPM there is a bar chart which shows CPM-440V and 440C having the same level of toughness. Yet shortly after this they quote charpy values for the two steels and 440C is ahead by 50%+.

When they quote numbers they are usually very specific about the soak times, quench methods and tempering specifics, and the resulting hardness and thus you know how to interpret them. However the charts I have found to be useless as not only do they differ from the numbers, they never tell you how they are heat treating the steels, and they give numerous recipes shortly after.

That aside, ATS-34 offers superior hardness, wear resistance and hot hardness over 440C. In regards to toughness, both are rather brittle stainless steels. Both are also rather prone to rusting, and will pit readily, as compared to something like 440A. They of course are far superior to something like 52100 which will take surface rust in minutes when exposed to fruit acids.

-Cliff

 

[Jerry Hossom]

Originally posted by Cliff Stamp
Regarding CPM, I would obviously not consider them (or anyone else) an unbiased source of information on the products that they sell.

That must be a pretty rough world up there in Newfoundland if you can't trust anything said by anyone who makes and sells a product!

Since most knifemakers, probably 90%, offer guarantees that their blades will perform according to the "information" they provide when a knife is purchased, or the customer can return the knife for a refund, I think most are careful to fairly state what they expect from a knife blade of their making and of the steel used.

As for the "information" you've just provided, I think it would have been useful to state that your experience with these steels is limited to just those knives with which you are personally experienced, and regarding which you have little knowledge of the manufacturing processes used - good or bad. Like your complaints regarding the information provided my Crucible concerning their steels, your comments concerning corrosion failure neglected to mention that you live in a salt air environment where such corrosion is expectedly above the norm. There are many who carry 52100 blades for years without experiencing any rust, but they probably use a light coat of oil on their blades to prevent that. They are usually those who treat their blades with some measure of respect and exhibit the same towards the people who have made them.

ATS-34, 154CM, and 440C are only brittle if the knife that employs them is poorly crafted or poorly used. Properly managed they have all served well under stress conditions that greatly exceed the needs of the average knife user.

 

[Cliff Stamp]

Jerry Hossom :

That must be a pretty rough world up there in Newfoundland if you can't trust anything said by anyone who makes and sells a product!

When someone is selling you something, no I would not judge them an unbiased source of information about the products they sell, nor about those that compete against them. This doesn't mean it is impossible to find those are are unbiased. I know several, but can only say that after many conversations with them about performance in detail.

The main critical points are will they discuss the negative aspects of performance, and with knives where are the performance bounds. The latter is important not only for the obvious reason, but also it shows you how much R&D they have done, and how much they are overbuilding the blade, which is directly related to the cutting performance being wasted.

... most knifemakers, probably 90%, offer guarantees that their blades will perform according to the "information" they provide ...

If someone is willing to provide a guarantee that their product will perform as they describe then that gives strength to their argument. However I have seen warrenties roll over when used, soI don't have blind faith in them either. As well, there are lots of behind doors problems also, for example, from Randall :

I can name a few of these makers because I just got through getting my ears full at Blade on them
and their "policy." Some makers will tell you something to save your feelings and then they never
deliver, and make a thousand excuses why they didn't.

http://www.bladeforums.com/forums/showthread.php?s=&threadid=205062&perpage=20&pagenumber=2

.. you have little knowledge of the manufacturing processes used

For some knives I know it in detail, as some makers will tell you exactly what they did. With others yes, you are left in the dark and always there is the wonder of the heat treating being the problem. Though of course when you see the same performance time and time again, this becomes less of an issue, as well when you develop a basic understanding of how materials properties influence performance.

... your comments concerning corrosion failure neglected to mention that you live in a salt air environment where such corrosion is expectedly above the norm.

First off, I was commenting on its exposure to fruit acids, not the air. Secondly, though I live right next to the ocean, the humidity is very low here, and surface rusting is not an actual issue except when it rains. Most people around here don't even oil their knives.

There are many who carry 52100 blades for years without experiencing any rust, but they probably use a light coat of oil on their blades to prevent that.

There are also people who enjoy sharpening, so by your logic you can't argue that the edge retention of some materials is greater than others, as their blades will always be sharp regardless of use. You can extend the same argument to make any properties irrelevant. For example, make your blades out of mild steel as with enough cross section, the durability will be enough. You only need to find someone to tolerate the low level of cutting ability.

ATS-34, 154CM, and 440C are only brittle ...

If hardened to the cutlery norm.

Brittle is a relative term and only has a meaning when used as such. Those steels are far more brittle than steels such as 5160. Can you make knives out of them. Of course. You can also make knives out of carbide and even glass, thus by your logic glass isn't brittle either.

If you promote a knife steel as tough, this means there must be something being used that is brittle, or else the tough designation is simply hype. It is the same with every other aspect of performance. The limits define each other and all inbetween.

-Cliff

 

[Jerry Hossom]

Cliff, kindly don't quote me out of context, or clip sentences then finish them in your own way to make an argument.

 

Jerry, what else can you expect from a mad scientist?

 

[Cliff Stamp]

The context is given in the above, if what you said was misrepresented you could clarify the context which is different than how it was given as it was rather straightforward.

As for the sentance clip, I was simply speaking on the platform you presented, though to be complete I should have included the rest of it but I thought it obvious that I was taking a different point of view.

-Cliff