A few Quick questions about D2.

[NJBillK]

Quite a few folks are under the impression that D2 takes a decent edge at best, but holds it for a Very long time. I can get my D2 knives shaving sharp without much issue.

Where the conflict starts is, a lot of folks will say that D2 needs a fairly thick edge to support the large carbides. The knives that I have in D2 are fixed blades and are all over .035 BTE.

1) How is this not the case with D2 traditional knives?
- A lot of Queen, Schatt & Morgan, and other brands use D2 for their knives, but many are brought down below .020 BTE and they do not experience edge failure.

2) Is this due to their expected lighter use?

3) Keeping in mind that the majority of these knives are slip joint in design, and the resulting lighter use; could it be that the alloy is essentially being pushed closer to its failure threshold, but only survives due to the strength of the alloy?

4) Is it likely that the manufacturers are betting on the steel being "strong enough" based on 90%+ of the uses being on the lighter end of the EDC spectrum (opening mail, boxes, trimming nails), as opposed to heavy side loading from whittling it poor technique, cutting knotty wood, or other stresses that overcome the lowered threshold duet the thinner cross sectional edge profile?
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I know it isn't likely that anyone would be able to answer all of these aside from some folks that have a particular type of education, or work experience. (Maybe mete would be kind to chime in?)

Also, if anyone has some solid ideas, answers, leads or information that may be willing to share, I am all ears.

That being said, if anyone has had a D2 traditional fail on them, or survive usage that they were expecting damage from, could weigh in, I would appreciate it.

Thanks folks.

 

[Kentucky]

D2 is a steel that's suffered from a factory "standard" heat treat that's terrible for cutlery. It's originalily a die steel and the standard heat treat left massive amounts of RA. 20%+. It often lead to chippyness'..then some custom makers tried different heat treats. Lower temper and cryo to reduce RA. It made big improvements over the aisi standard heat treat for d2 dies. I think way back that attributed to the "takes a crappy edge and holds it forever" deal..

 

[mete]

Back to the basics. Sharpness - the minimum radius that a steel can be ground
The large carbides limit the sharpness . when you have done your best at sharpening D2 , with wear the carbides will eventually breakout so that establishes the texture of the edge and sharpness.
I haven't seen much said about powder metal D2 so I can't comment there.

 

[Lapedog]

Quite a few folks are under the impression that D2 takes a decent edge at best, but holds it for a Very long time. I can get my D2 knives shaving sharp without much issue.

Where the conflict starts is, a lot of folks will say that D2 needs a fairly thick edge to support the large carbides. The knives that I have in D2 are fixed blades and are all over .035 BTE.

1) How is this not the case with D2 traditional knives?
- A lot of Queen, Schatt & Morgan, and other brands use D2 for their knives, but many are brought down below .020 BTE and they do not experience edge failure.

2) Is this due to their expected lighter use?

3) Keeping in mind that the majority of these knives are slip joint in design, and the resulting lighter use; could it be that the alloy is essentially being pushed closer to its failure threshold, but only survives due to the strength of the alloy?

4) Is it likely that the manufacturers are betting on the steel being "strong enough" based on 90%+ of the uses being on the lighter end of the EDC spectrum (opening mail, boxes, trimming nails), as opposed to heavy side loading from whittling it poor technique, cutting knotty wood, or other stresses that overcome the lowered threshold duet the thinner cross sectional edge profile?
-------
I know it isn't likely that anyone would be able to answer all of these aside from some folks that have a particular type of education, or work experience. (Maybe mete would be kind to chime in?)

Also, if anyone has some solid ideas, answers, leads or information that may be willing to share, I am all ears.

That being said, if anyone has had a D2 traditional fail on them, or survive usage that they were expecting damage from, could weigh in, I would appreciate it.

Thanks folks.

Even the larger carbides in D2 are extremely small. I doubt there is an edge that is thin enough that it is not able to support these literally microscopic carbides.

 

[HeavyHanded]

D2 carbides range from single digits up to 20 micron or so - that's pretty big in terms of carbide formation in blade steel where the average apex starts out < 1 micron.

At a guess I'd say the more traditional knives using this steel are run to a higher Rockwell or as Kentucky mentioned the HT is just plain done better, which really seems to make a huge difference. I have tested a D2 blade HT'd by Bluntcut and it held a great edge at very low angles. My Eskabar can also hold a pretty low edge but it definitely doesn't hold that edge as long as the BCMW flavor.

 

[Obsessed with Edges]

I have a pet project knife in D2 (by Queen, with heat treat by Peters Heat-treating). I call it a 'pet project', because my mission since I've owned it is to keep gradually thinning the grind on it's blades. It's a stockman pattern, and I use the sheepfoot blade a lot. Nothing real heavy or abusive, but standard chores like opening boxes, cutting cardboard & other packaging, etc. I've come to the conclusion that the perception it can't take or hold a fine edge is pure nonsense, at least as applied to my own example knife. I've thinned it down to < 25° inclusive at the edge (very thin, shallow convex). I've tended to keep the finish on the edge more polished, down to 2-5 micron finish or so (using alox compound like white rouge on a denim strop), and it's been working and holding up just fine. I've been more disappointed when I've left it a little coarser, in the 600-1200 range (diamond), as I've noticed the edge character changes pretty fast in use, and I've needed to touch it up more often, to keep it in that Fine/EF biting type of sharpness.

I HAVE heard or read that maybe D2 is more sensitive to proper (or improper) heat treat. So, with that qualification, I'd just say if it's done right, there's little or no reason to worry about it.

As to the size of the carbides in non-PM (ingot) versions of D2, the carbides are very large as compared to the thinness of a shaving-sharp apex, which should be down to < 0.5 micron. The chromium carbides in ingot D2 can get up to ~ 50-100 microns at times. The key in refining them at the apex is to use an abrasive that's fully capable of shaping and thinning them to a shaving-sharp geometry ( * see below). If that can't be done, then they will remain too big/thick, and can't be supported by the matrix steel at the edge.

* For grinding/hogging off metal, SiC or diamond works well on D2. For full thinning of the apex to shaving sharpness, I like diamond through Fine/EF at least, if not EEF as well. ONLY after that, some careful stropping on hard-backed denim with a good aluminum oxide compound works very well, taking it to a pretty nice polish. I like white rouge compound, in particular, for that.


David

 

[M-S-T]

I had three different blades in D2 ( from different manufactures) and one thing I noticed is that D2 doesn't like shallow angles. At 15 per side it gets really chippy. With 20 per side it holds the edge really good.

 

[Dean51]

No proof but I've heard D2 shound not go below 15 DPS.
Like M-S-T I've got D2 from 3 makers all are 18 DPS with a 600 silicon carbide stone.
I have never had a chipping problem with any of them.

 

[Lapedog]

D2 carbides range from single digits up to 20 micron or so - that's pretty big in terms of carbide formation in blade steel where the average apex starts out < 1 micron.

At a guess I'd say the more traditional knives using this steel are run to a higher Rockwell or as Kentucky mentioned the HT is just plain done better, which really seems to make a huge difference. I have tested a D2 blade HT'd by Bluntcut and it held a great edge at very low angles. My Eskabar can also hold a pretty low edge but it definitely doesn't hold that edge as long as the BCMW flavor.

But is that the vanadium carbides that are that large or the chromium carbides?

The reason I ask is because chromium carbides are obviously not as hard as vanadium ones and I thought they would have been sharpened and thinned out as it comes to an apex. Of course providing sharping media hard enough to cut the chromium carbides is used.

 

[Obsessed with Edges]

But is that the vanadium carbides that are that large or the chromium carbides?

The reason I ask is because chromium carbides are obviously not as hard as vanadium ones and I thought they would have been sharpened and thinned out as it comes to an apex. Of course providing sharping media hard enough to cut the chromium carbides is used.

D2 doesn't have a lot of vanadium anyway; only up to about 1% or so. It's chromium carbides make up most of it's wear resistance. Their extreme large size accounts for most of it's sharpening challenges, and not so much about their hardness, which is managable with the right abrasives and much, much easier with something like SiC or diamond, in particular. There's a noticeable threshold in ease of sharpening D2, if comparing something like aluminum oxide stones, which can do it, but are slower, to silicon carbide or diamond, which will both eat it up, and fast.


David

 

[HeavyHanded]

But is that the vanadium carbides that are that large or the chromium carbides?

The reason I ask is because chromium carbides are obviously not as hard as vanadium ones and I thought they would have been sharpened and thinned out as it comes to an apex. Of course providing sharping media hard enough to cut the chromium carbides is used.

I don't think D2 has enough V to form carbides. But yeah, as long as the abrasive can shape them the Chromium carbides will get cut to size. How much of an anchor might be needed is speculated in the 20°/side range but that doesn't include individual observations. I guess that's part of the question asked by the OP and I don't have an answer.

Here's a pic of some D2 that's been etched to show the carbides.

Second pic is a closer look after 1/2 hour - you can see some of the carbides along the edge.

 

[Lapedog]

I don't think D2 has enough V to form carbides. But yeah, as long as the abrasive can shape them the Chromium carbides will get cut to size. How much of an anchor might be needed is speculated in the 20°/side range but that doesn't include individual observations. I guess that's part of the question asked by the OP and I don't have an answer.

Here's a pic of some D2 that's been etched to show the carbides.

Second pic is a closer look after 1/2 hour - you can see some of the carbides along the edge.

You are the freakin' man!

I had looked at the composition of d2 while reading this thread to refresh my memory. I had seen the low vanadium and wondered if it was enough to form V. Carbides.

So from your edge magnified shots we can clearly see where the chromium carbides havs fallen off the edge. A sighting of d2's mythical "toothy" edge perhaps?

Now here's my follow up question.....

How much do you think those voids left in the edge lead to further edge degradation? I would assume that is where the edge will be most susceptible to damage.

 

[HeavyHanded]

You are the freakin' man!

I had looked at the composition of d2 while reading this thread to refresh my memory. I had seen the low vanadium and wondered if it was enough to form V. Carbides.

So from your edge magnified shots we can clearly see where the chromium carbides havs fallen off the edge. A sighting of d2's mythical "toothy" edge perhaps?

Now here's my follow up question.....

How much do you think those voids left in the edge lead to further edge degradation? I would assume that is where the edge will be most susceptible to damage.

I don't really know how hard the actual steel is.
One of the really neat things these pics show - the 1/2 hour soak shows a lot of carbides anchored in the edge as shiny bits. In fact it almost looks like the steel has been eaten away leading to increase in the amount of carbides left. The pic after a few hours of soak shows all the carbides gone from the edge region.

I still don't know how much you can draw from this. To me it says the obvious - a certain amount of mechanical attachment is needed to secure the carbides. The carbides can be shaped into the edge and will form a substantial percentage of the exposed surface. The remaining carbides show scratch marks from ALumOx abrasive but that doesn't indicate if diamond or SiC is a better choice (IMHO they are).

To me this shows the carbides along the edge break down or are broken loose and the remaining edge is going to be uneven, somewhat broad, and be made up of largish carbides that are well anchored. If shaping them with a specific abrasive will improve their anchor I really don't know.

I prefer to grind D2 thin but at a relatively rough finish - coarse DMT or fine Crystalon at 26-28° inclusive.