Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

daberti said:
Edge stability Jim, that's it and almost certainly a more favorable V carbides/Cr carbides ratio. I also guess that Darrin HTd in a certain way, so that he managed also to achieve great stain resistance AND residual cementite close to nil.
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Yes Darrin did a great job on it. :)

Looking forward to see how it does long term. :thumbup:
 
I've been wondering how niobium (columbium) has an effect on the steels matrix. I know it is a former of very small hard carbides. It improves ductility,wear,hardness and corrosion resistance but how does it react along with Vanadium,molybdenum,tungsten and chromium. Is having another carbide type in the matrix giving us something?
 
darrin sanders said:
That's the good thing about S35VN, you get excellent edge retention with fairly easy grinding and finishing. On this particular knife I only drilled and profiled before H/T and it only took about 1.5 hours to grind and finish this blade to a 600X hand rubbed finish after H/T. And that included etching my mark as well.
That's why I said that I think this alloy is great for knifemakers. Great performance with a reasonable finish time. Time = $$ in my shop. LOL
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I'm working with a blade right now and I'm liking what I see so far:)
 
Phil Wilson said:
Lance may chime in again but he did a forced patina when he first received the knife. I got it back from him through Jim so I could take a look at it. I did have some darker patina on it and a few spots that were very shallow pitting. I cleaned it up with very little effort, basically some work with medium (maroon) Scotch Brite. I was surprised that there was not more corrosion given that this knife was used around salt water. Phil
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Hi Daberti, as Phil noted, I have had very few corrosion issues with that knife in m4. Lots of exposure to high corrosion environments (though this one does NOT get used on the kayak) and I have had almost no corrosion at all. Cleaning and maintenance has been diligent but very minimal. Basically that means rinse and wipe after use.

I would note though that I have two of these knives with slightly different heat treats....Phil can provide more information about that. I don't know the specifics, but the first one i believe is slightly harder than the second. It has been my impression so far that the second knife (which I believe Phil said was in the 63-64 range as opposed to the first which i think was about 65) has been a bit more prone to oxidation. Twice now I have caught that one with a bit of very light red surface pitting starting. It has been trivial to remove but this is an issue that i have not yet experienced with the first knife. I have not shared this info with Phil yet, so I'd be curious to hear his thoughts here. Not sure if that data makes any sense given the heat treats of the two blades but I would be curious to find out.

FWIW, I have not noticed any significant differences in edge retention or edge stability between the two blades.
 
Lance,

Are the surface finish the same? Or maybe even with same surface finish, the micro structure is different enough due to hardness that the surface of the softer one catches/traps moisture more?
 
waterstoneblades said:
I've been wondering how niobium (columbium) has an effect on the steels matrix. I know it is a former of very small hard carbides. It improves ductility,wear,hardness and corrosion resistance but how does it react along with Vanadium,molybdenum,tungsten and chromium. Is having another carbide type in the matrix giving us something?
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0.5% niobium will form very few carbides here if any.
When it forms Niobium Carbides (or Nitrides) these particles will be able to effectively pin the austenite grain boundaries (from an intra-grain location) at temperatures up to 2000ºF= 1093.333ºC (austenite grain reduction by Particle Drag). The same effect is achieved by V, Ti and Al.

Grain boundary drag is -on the other hand- what it is brought about by the 4 major alloying elements, Mn, Cr, Mo and Ni, which are not particularly effective at forming fine particles that will give a strong particle drag effect as do Nb, Ti, V and Al. But they will produce a grain boundary drag effect and can therefore reduce the rates of grain growth as well, but to fairly lower extents.
 
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Surfingringo said:
Hi Daberti, as Phil noted, I have had very few corrosion issues with that knife in m4. Lots of exposure to high corrosion environments (though this one does NOT get used on the kayak) and I have had almost no corrosion at all. Cleaning and maintenance has been diligent but very minimal. Basically that means rinse and wipe after use.

I would note though that I have two of these knives with slightly different heat treats....Phil can provide more information about that. I don't know the specifics, but the first one i believe is slightly harder than the second. It has been my impression so far that the second knife (which I believe Phil said was in the 63-64 range as opposed to the first which i think was about 65) has been a bit more prone to oxidation. Twice now I have caught that one with a bit of very light red surface pitting starting. It has been trivial to remove but this is an issue that i have not yet experienced with the first knife. I have not shared this info with Phil yet, so I'd be curious to hear his thoughts here. Not sure if that data makes any sense given the heat treats of the two blades but I would be curious to find out.

FWIW, I have not noticed any significant differences in edge retention or edge stability between the two blades.
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Surferingo, I'm having quite an exchange of emails with Phil, and I humbly submitted to him some literature and ideas on M4 (and not only) HT.
Relating to your knives and avoiding to disclose Phil's own HT: CPM-M4, BU S690, but also Vanadis 23, Vanadis 30 and Vanadis 60, are quite clever steels.
If you heat treat them with a certain combination of austenization/tempering temps, what you will get will be W Carbides and V carbides only.
No Cr carbides and very few (if any) Moly carbides.
So: see my post #2446 here as far as grain size/toughness is concerned.
As far as stain/corrosion resistance is concerned, theoretically you'll have nearly all Cr and Moly available to deal with this.
I've already mentioned the PRE number and its formula above. As a matter of facts the second knife might have been HTd just out of the magic spot Phil had found with the other one, but expect some news from him ;)

Probably you did NOT notice any edge holding difference among the two blades because, as this thread demostrates- edge holding -ceteribus paribus (geometry, edge angle, etc)- depends upon two major factors: adhesive wear resistance and abrasive wear resistance. Where cutting only manila rope or carboard would call for the latter.
Thus I wouldn't be suprised if you saw in your own cutting requirements more edge holding with a Vanadis 60 blade, which can go up to 69HRC than with a Vanadis 10 one @65.
 
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daberti said:
Surferingo, I'm having quite an exchange of emails with Phil, ....
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I would love to read those. If you got his permission, would you be willing to put those into a separate thread - assuming there's no personal stuff?
 
sodak said:
I would love to read those. If you got his permission, would you be willing to put those into a separate thread - assuming there's no personal stuff?
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Sodak, I think Phil will put himself the results of them either on his own site or here
 
Some back ground on Surfinggringo's ( SG's ) CPM M4 knives.

He wanted a fish processing knife with a shorter stiffer blade than the normal fillet and had a preference for CPM M4 since he likes the characteristics of that grade. He was not concerned with corrosion since it was not to be used on the Kyak and he planned to keep it clean and dry after use and before putting it away. I am familiar with the type of fishing he does and knew he would be cutting through some large bones and scales. My criteria is to optimize wear resistance, toughness and edge holding with steels in this category. Normally these knives are used in hunting situations where edge holding is primary so that the blade has a good bite and will last through the field processing and subsequent quartering and butchering. CPM M4, CPM 10V and the other A11's we have available are examples of these grades. None of these have enough corrosion resistance alloy in the mix to be considered stain resistant. CPM M4 a little better due to the moly in the matrix that can help to reduce pitting. Both of these CPM M4 knives that SG has are test knives. I was interested in providing enough toughness (ductility) to handle the fish bones and edge holding so that the knife would not have to be resharpened after every session. This would provide some feed back on this application as well as other field applications on large game. The edge was ground heavier than what I normal do to provide some insurance on bones and scales and at RC 65 is pushing the envelope on ductility. Based on feed back from the first knife the second was ground a little thinner at the edge. Both blades were heat treated the same except the second one saw 20 degrees more in the tempering and dropped about one point. Based on SG's initial reports the edge held up well even though he pushed it pretty hard. He likes to keep his knives popping sharp so he did not go long enough between sharpening to get a good fix on that. My own tests on cutting rope, cardboard and wood proved that edge holding was where I wanted it based on all the other variables. Jim's test also gave me good feed back and we pretty much came up with the same results using different test methods. Now I have good feed back on edge performance and toughness on this one knife and one particular heat treat.

The corrosion resistance to me here is a side issue but gives us some indication of how this grade does around an corrosive environment if it is maintained rigorously. Both blades were finsined the same with a 400 grit satin along the length of the blade. SG did not mention that he “forced patina” the first blade. I got it back here before it went on to Jim to test and did a light re-grind to remove the patina and some very light pitting. If came off with just a few passes on a 320 SC belt and some rubbing with scotch brite. My main concern with corroson here is loss of edge. It does not take much to errode away a few mills of steel and can even have more effect than abrasive wear.

CPM M4 is not the grade I would recommend for this application. I would look at CPM S30V or 35VN, Elmax, CPM 154. SG currently has one of my fillet knives with CPM 154 and I am sure I will get good feed back on that one. This guy uses his knives and is one hell of a fisherman.

As far as heat treat I am basiclly following the Crucible data sheet and used multiple SH tempers on these blades as reccommended by the guys who use this grade for actural industrial applications. This method gave me the wear resistance and toughness I was looking for. I may later try some deep cryo and low temper experiments as well based on some information from Daberti.

Daberti has provided me with some great tech information and papers and I appreciate any help I get especially with some of the Bohler-Uddeholm grades he has experience with. Thinking of a fillet knife with ELMAX and that should be a good test bed. Phil
 
daberti said:
0.5% niobium will form very few carbides here if any.
When it forms Niobium Carbides (or Nitrides) these particles will be able to effectively pin the austenite grain boundaries (from an intra-grain location) at temperatures up to 2000ºF= 1093.333ºC (austenite grain reduction by Particle Drag). The same effect is achieved by V, Ti and Al.

Grain boundary drag is -on the other hand- what it is brought about by the 4 major alloying elements, Mn, Cr, Mo and Ni, which are not particularly effective at forming fine particles that will give a strong particle drag effect as do Nb, Ti, V and Al. But they will produce a grain boundary drag effect and can therefore reduce the rates of grain growth as well, but to fairly lower extents.
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Thanks for your input daperti! You go into great detail and explain it well.
 
Here is a photo of SG's knife taken today for reference. :)

DSC_5341.JPG
 
Phil Wilson said:
Some back ground on Surfinggringo's ( SG's ) CPM M4 knives.
As far as heat treat I am basiclly following the Crucible data sheet and used multiple SH tempers on these blades as reccommended by the guys who use this grade for actural industrial applications. This method gave me the wear resistance and toughness I was looking for. I may later try some deep cryo and low temper experiments as well based on some information from Daberti.

Daberti has provided me with some great tech information and papers and I appreciate any help I get especially with some of the Bohler-Uddeholm grades he has experience with. Thinking of a fillet knife with ELMAX and that should be a good test bed. Phil
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Thanks Phil for your kind words of appreciation :)
M390 would be even a better steel in salted environment, the best probably being Vanax about which we'll talk via email.
 
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