ZDP-189 and Cowry-X: Overrated or Super Steel?

[Larrin]

New research on ZDP-189 analyzing its toughness, edge retention, and corrosion resistance. How does it achieve such high hardness? Is it really stainless? Does it have any toughness at such high hardness? https://knifesteelnerds.com/2019/12/30/zdp-189-and-cowry-x-super-steel-or-overrated/

 

[bseven]

This is amazingly good info, thanks for doing the work and Happy New Year!

 

[Kippington]

Great read - it answers a lot of questions and helps put things in perspective for me. I now have a better idea of steels I haven't tried, which one's I'd like and why. I definitely have a preference for higher carbide % steels.

When I bought ZDP it was marketed as a semi-stainless. It fits that label quite well as it deals with kitchen jobs with a light patina but no rust, about the same as other steels marketed under the same label.
In my experience I'm actually surprised at how tough it is, but I must've tempered mine more by sticking it in the deep-fryer haha!

 

[Larrin]

Depending on usage hardness can matter more than toughness.

 

[M1k3]

Great read - it answers a lot of questions and helps put things in perspective for me. I now have a better idea of steels I haven't tried, which one's I'd like and why. I definitely have a preference for higher carbide % steels.

When I bought ZDP it was marketed as a semi-stainless. It fits that label quite well as it deals with kitchen jobs with a light patina but no rust, about the same as other steels marketed under the same label.
In my experience I'm actually surprised at how tough it is, but I must've tempered mine more by sticking it in the deep-fryer haha!

Please tell me the fryer was located at a restaurant that you may or may not of worked at.

 

[bahamaroot]

Great read, very informative! Thanks for another excellent article.

 

[Kippington]

Please tell me the fryer was located at a restaurant that you may or may not of worked at.

You know that Back of House reflective test to see if your oil is still good? The mirror polish on my Sukenari worked a treat haha!

 

[bseven]

Depending on usage hardness can matter more than toughness.

Could you outline some usage scenarios where this is true?

 

[Larrin]

Could you outline some usage scenarios where this is true?

Hardness is a measure of strength. Higher strength means resistance to edge rolling and deformation which is most significant with thin, low angle edges. Toughness matters most in impacts though can also show up in lateral stress to the edge. But with thin edges lateral stresses seem to lead to edge rolling even in relatively brittle steels. But even relatively small impacts can lead to chipping in the same edges.

 

[Luftmensch]

Interesting read @Larrin! Thanks for the research and sharing.

The article explains a lot!

There are many other steel choices that can achieve high hardness and/or edge retention if stainless levels of corrosion resistance are not required, making ZDP-189 much less special. Because of the false advertising of this steel as being “stainless” I give ZDP-189 the Knife Steel Nerds “Most Overrated Steel” award.

Perhaps a little harsh . But I have empathy for the position! I was never sold the idea it was the bees knees of steels - just that it was a high hardness, high edge retention, semi-stainless steel - and this it appears to be?

When I bought ZDP it was marketed as a semi-stainless

Similarly. To be fair I have more often seen ZDP-189 described as stain resistant not stain proof. In that regard it does stain less... And from a kitchen knife point of view practical enough.

@Larrin,

I know you do these reviews from a general point of view (all uses of the steel). Given this is KKF, do you have a gut feel on how tough a kitchen knife has to be to be useful. During proper usage, at the worst kitchen knives might see a brutal day of work on a plastic board. But we dont need to chop through logs.... Although ZDP is not a particularly tough steel, I find that while it does not hold a razor edge for very long it holds a functionally sharp edge for a long time.


(Happy new year!)

 

[XooMG]

Cheers. I have a discontinued Chinese-style slicing cleaver in Cowry-X and it was, according to the seller, tempered back to hrc~63. Never gave it that much thought since I'm pretty gentle on edges, but it's nice to read some breakdown on the material.

 

[Larrin]

Interesting read @Larrin! Thanks for the research and sharing.

The article explains a lot!



Perhaps a little harsh . But I have empathy for the position! I was never sold the idea it was the bees knees of steels - just that it was a high hardness, high edge retention, semi-stainless steel - and this it appears to be?



Similarly. To be fair I have more often seen ZDP-189 described as stain resistant not stain proof. In that regard it does stain less... And from a kitchen knife point of view practical enough.

You are rewriting history a bit. ZDP-189 is marketed as a stainless steel, including by its manufacturer (Hitachi). There are certainly forum discussions about the steel having poor corrosion resistance, but those are typically debates. People continue to argue with me about it being a stainless. I can say definitively it is not a stainless, therefore it is overrated without hyperbole. Overrated at the very least by the manufacturer and the vast majority of knife producers and sellers which are getting their information from Hitachi. The fact that Hitachi calls it a stainless means they are either dishonest or incompetent, so calling the steel overrated is kind, in my opinion. I could have been much more harsh. The whole point of the steel is that it can achieve high hardness even though it is stainless. But it’s not stainless.

 

[Kristoffer]

An interesting read, as always! Thank you.

Did you by any chance come across anything that might explain or substantiate the claims that have been heard about ZDP-189 loosing its initial sharpness relatively quickly, but then staying functionally sharp for a very long time?

 

[ma_sha1]

Amazing article, so informative & data driven!

Now, they’ll need to invent a new super steel to start a new hype. After all, the addiction needs new steels to justify ever expanding collection.

 

[Larrin]

An interesting read, as always! Thank you.

Did you by any chance come across anything that might explain or substantiate the claims that have been heard about ZDP-189 loosing its initial sharpness relatively quickly, but then staying functionally sharp for a very long time?

That is a common claim about high wear resistance steels, it’s not exclusive to ZDP-189. I don’t know if it is a “real” property of the steels or if it is a perception thing.

 

[Luftmensch]

ZDP-189 is marketed as a stainless steel, including by its manufacturer

Fair enough. I am not trying to contradict you! I have never looked at the datasheet.

To be fair I have more often seen ZDP-189 described as stain resistant

I'll concede this is an exaggeration. Human folly though, not tantamount to rewriting history

The fact that Hitachi calls it a stainless means they are either dishonest or incompetent

Probably dishonest. You know what happens when the marketing department get hold of things...

I could have been much more harsh

Hehe... I kinda wanna see what that would look like!

 

[Larrin]

Hehe... I kinda wanna see what that would look like!

When I’m ready to sellout and start writing clickbait articles.

 

[kayman67]

https://www.hitachi-metals.co.jp/e/yss/search/zdp189.html

I see here they don't use carbon when they should, either. Who knows how they consider things. If one would have no idea about anything, this would be misleading for sure.

I've always considered this a semi-stainless.

 

[Luftmensch]

Did you by any chance come across anything that might explain or substantiate the claims that have been heard about ZDP-189 loosing its initial sharpness relatively quickly, but then staying functionally sharp for a very long time?

I made that observation earlier in the thread. Let me qualify that a little further; the meaning of relative? I mean relative to the interval between sharpening - not other steel. I do not think initial sharpness disappears any quicker than any of the other 'simpler' high-carbon steels I have used.

For instance, say I sharpened both ZDP189 and white steel. They'll both start out popping hairs. After some use, they will stop popping hairs but they will still cut tomatoes perfectly. This probably occurs at a similar level of use (I have never even remotely considered actually quantifying this). If there is a difference, I doubt it would be interesting. At some point they will stop cutting tomatoes nicely... This is where I would resharpen and where there is a big difference between the steels. ZDP can last a long, long time.

In this scenario ZDP might be a razor for 1% of use between sharpenings whereas the white steel might achieve 10%. If they both pop hairs for a day, the white steel is getting sharpened on a 10 day cycle and the ZDP is getting sharpened on a 100 day cycle.

From my point of view, there aren't many cooking tasks that require razor level sharpness. This is why I like to describe it as 'functionally' sharp. Others may have a different point of view! But if you are a home cook and adopt the same (lazy?) attitude towards sharpness... you can go for months without sharpening.

I have no doubt this is common to hard and high wear resistance steels.

 

[Luftmensch]

When I’m ready to sellout and start writing clickbait articles.

"The shocking truth about stainless steels that Hitachi doesn't want you to know"
"These unbelievable quenching tricks will change your life"
"Need to get your steel hard? These herbal supplements rock well"

 

[WildBoar]

"The ten most revealing photos of today's hottest starlets -- and some knife info."

 

[captaincaed]

Man, cool read. Savage.

Seems like an oddball steel certainly. My lived experience is similar in that you get a functional kitchen edge for a long time, but I'm going to make a greater effort to clean and dry from here on out. Nice to know the carbides shouldn't be awful to sharpen.

As an aside, is anyone laminating the SxV steels for knives so they're not a bear to thin?

 

[OldJoeClarke]

Great article, just what I needed to read at this moment in time.
I have been on and off about buying the Hamono San ZDP Bunka for some time and recently the urge to buy, buy, buy has come back. ZDP never comes cheap and is made to sound like the utopia of knife steels and I am guilty of being partially lured into that thinking.
I do have a passion for the Shiro's and Ao's and a decent skill level when it comes to the stones but ZDP is the one steel that my collection is missing. Am I buying it for the wrong reason, can it be that much better than Ao super at 65hrc?
Slowly I think I am moving away from it, very slowly though...

 

[Nagakin]

Am I buying it for the wrong reason, can it be that much better than Ao super at 65hrc?

My coworker has the same knife and in a professional setting, it's not my favorite. It takes a long time to sharpen and the fresh feel is gone quickly. It's almost pointless getting it to a razor. The functional edge does last forever, but in a volume kitchen razor sharp is more speed with less strain. Personally part of the appeal of a nice knife to me is also maintaining it.

If it was cheaper I can see how a line grunt at a slower place might be happy having never having to sharpen, but at this price point...R2/SG2 is superior to me because it's cheaper, easier to sharpen, and responds well to honing/stropping. My workhorse blue super is only at 63 and it's not even a contest which I prefer.

 

[OldJoeClarke]

[QUOTE="Nagakin, post: 672883, member: 38579"R2/SG2 is superior to me because it's cheaper, easier to sharpen, and responds well to honing/stropping. My workhorse blue super is only at 63 and it's not even a contest which I prefer.[/QUOTE]

Sage advice right there, I do spend a lot of time looking at and buying stones and making strops with various grades of compounds, with a huge box of bits and bobs all knife sharpening related so I guess I am in the same line of thought as you and would miss the tinkering and sharpening part with such a knife.
Ironically, I just finished prepping some jerk chicken from making the marinade to boning the thighs all with the same knife.... A Dao Vua leaf spring Kiri cleaver for £60 that I lovingly fixed up and it was a joy. Wont stay sharp for to long but gets nasty sharp in minutes, the total opposite of ZDP.
Cheers Nagakin for you thoughts...

 

[NO ChoP!]

I dont think people claim it loses its initial edge quickly. More like when it does, it will hold at that useable 85% sharp forever. Which is probably by definition, edge retention; not some stellar achievement found only in zdp.

 

[kayman67]

Why is this hard to sharpen? The diamond strop takes it to razor sharp much easier than most alloys and the edge is very stable.
It's not perfect, but looks more and more like another VG10 situation.

 

[Nagakin]

Quickly is relative to what you're doing. I've only used one instance of ZDP, but to me it's a PM problem in general. Doesn't stop me from loving R2 the way I do. Main difference is that I can irresponsibly hone R2 on a ceramic rod to fresh in a hurry without worrying. I rarely have time for real maintenance until after service.

Why is this hard to sharpen? The diamond strop takes it to razor sharp much easier than most alloys and the edge is very stable.
It's not perfect, but looks more and more like another VG10 situation.

I'd call it time consuming relative to anything else you might sharpen, over hard.

VG10 is at least cheap though. A Shun rep sold our place a box of chef knives from their classic line for like $40 a piece and it's hard to beef with that. I regifted mine for a wedding I was going to skip, but it was a fair upgrade for our some of our guys.

 

[kayman67]

I agree that a ceramic rod with ZDP-189 won't work very well. It takes a bit of work even with my tungsten (that eats VG10 for breakfast for example). But I managed to set up a strop with diamond paste and that makes things very straightforward.
ZDP-189 kitchen knives are easy to maintain with some ceramic/diamond stones, in hand, but this requires some getting used to. Even better, Venev has in Russia some nice narrow long plates. Gritomatic doesn't sell them. I found this as I also deal with outdoor/bushcraft stuff, that's much more demanding and I had to test different options for maintenance that actually works on the go.
For me, hard to sharpen is CPM REX 121 for example. Very difficult to work with, regardless of what I use. Setting a new bevel on a hunting knife is a challenge. I would do ZDP-189 all day long instead.

 

[inferno]

I've only used one instance of ZDP, but to me it's a PM problem in general. .

i think its the same with all high alloyed SS powder or ingot. if it has lots of carbides and is hard you know its gonna keep that sharp but not scary sharp edge for a long time.
and the fresh off the stones sharpness disappears in like 2 minutes.

but its the same with carbon. the just dull a bit different, and now you have corrosion to add to the dulling too. and there is less carbides in it so it wont keep that "85%" edge for a long time. instead its a linear curve (lol) down to dull from the first cut. and also the carbides the common carbons have are cementite (iron carbide) and blue has tungsten carbides. but powder ss usually have lots of V/Mo/Cr/Nb carbides and sometimes nitrides on top of that.

i have noticed most high hardness high alloyed steels basically chip out when they dull. many small chips, even from cutting things like cardboard, and carbon/low alloyed ss basically just get round at the edge.
funny thing is that these types of steels can be at a similar sharpness for the same amount of media cut. the powder steels/high alloyed can be sharp between the chips, and the low alloyed just dull all over. both are still unusable though.

i think blue 2 at 62-63 is hard to beat when we take sharpening in consideration. also aus 8 is really good since it get just as sharp as carbon and never chips out (for me).
so yeah i kinda like the lowest grade stuff