Zapp Z-Wear experience and heat treat

[Willie71]

I shoot for edge stability. I grind my knives for cutting performance. Prying is left to pry bars or knives in 3V that are ground for it. Even then i rarely pry with knives. I would rather the edge handle being thin, or handle chopping, etc.

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Z-wear is what you want then. :thumbup:

I'll be doing some destructive tests over the next little while with z-wear with different heat treats. I'll be comparing 3v at Rc60 and Rc62 for reference.

 

[BluntCut MetalWorks]

Fine grain size(GS) is a relative comparison for steels within austenite temperature range. Fine gs for 12+%Cr steels would be ~ASTM 7 - e.g. aebl, niolox,... Off my head, 4-8%Cr gs ~astm 8, e.g. xwear, 3v. 0-3%Cr, ~astm 9-10, e.g. O1, 52100, ...

btw: astm 7/32um, 9/16um, 10/11um.

Here is fun count # of grain per 1 cubic mm for grain dia 32um vs 11um < using v=(4/3)pi*r^3 > ~ 58285 vs 1398845 (~24x of 32um).

Z-wear also has almost 3% vanadium, which is great for pinning grain boundaries, preventing grain growth, which both help toughness. The way I conceptualize this is anywhere I would use L6, 80crv2, or 5160, I would go with 3v. If I was going to use W2, 52100, or O1, I would go with z-wear. Z-wear is tougher at Rc62 than 3v is at Rc62 or higher. At Rc60 or below, z-wear can never match 3v toughness.

I've done things with z-wear at Rc63/64 that would have damaged a W2 edge of the same thickness at Rc62 without damaging the z-wear.

 

[kuraki]

Z-wear also has almost 3% vanadium, which is great for pinning grain boundaries, preventing grain growth, which both help toughness. The way I conceptualize this is anywhere I would use L6, 80crv2, or 5160, I would go with 3v. If I was going to use W2, 52100, or O1, I would go with z-wear. Z-wear is tougher at Rc62 than 3v is at Rc62 or higher. At Rc60 or below, z-wear can never match 3v toughness.

I've done things with z-wear at Rc63/64 that would have damaged a W2 edge of the same thickness at Rc62 without damaging the z-wear.

That's a perfect analogy I think.

 

[hugofeynman]

I think Vanadis 4 extra is inserted in this steel group also, so I'm very interested in this 400F (with cryo) vs 1000F temper. How to avoid secondary hardness in Vanadis 4 extra and deal with RA.

400F tempering is to avoid secondary hardening which will having carbide participated in larger amount thus lower toughness and corrosion resistance.

This applied applied to many tool steel with some amount of CrMoV like D2, 3V, M390, S30V etc.

But we need continuous cryo as part of the primary quench to deal with RA problem.

On some steel with too much alloy content such as most high speed this properly not a very good idea because of the amount of as quenched RA would be too high to be solve with the cryo and 1000F tempering is the only proper way to go.

For Cru-Wear type of steel it is pretty much in the middle between cold work tool steel and high speed. It fall into the "matrix high speed steel" so I'm not sure if the modified fast cryo => 400F tempering gonna be a good option.

 

[Willie71]

I think Vanadis 4 extra is inserted in this steel group also, so I'm very interested in this 400F (with cryo) vs 1000F temper. How to avoid secondary hardness in Vanadis 4 extra and deal with RA.

With the similarity in composition with z-wear/cru wear, I suspect it would need full cryo, not just sub zero to complete the conversion to martensite.

 

[hugofeynman]

Thank you, Willie71. My friend Metallurgist says there's no real benefit of going lower than -85C(-121F), but he usually high temper Vanadis 4 extra.

Until now all my Vanadis 4 extra blades have been high tempered, but with these low temper "new" theories I guess I'll have a try on cryo followed by low temper (first need to convince my maker). Can't wait for your conclusions before doing that!&#128512;

With the similarity in composition with z-wear/cru wear, I suspect it would need full cryo, not just sub zero to complete the conversion to martensite.

 

[Willie71]

Thank you, Willie71. My friend Metallurgist says there's no real benefit of going lower than -85C(-121F), but he usually high temper Vanadis 4 extra.

Until now all my Vanadis 4 extra blades have been high tempered, but with these low temper "new" theories I guess I'll have a try on cryo followed by low temper (first need to convince my maker&#128514. Can't wait for your conclusions before doing that!&#128512;

Your metallurgist friend is likely correct, when we consider dry ice/acetone only goes to -95 or -100f. Cryo might be overkill, but it does get past -121f. With cryo, there is the issue of eta carbides with a 6h plus soak. It's interesting stuff. :thumbup:

I looked up vandis 4e. It's higher alloy than z-wear.

 

[samuraistuart]

Vanadis 4e is very similar to M4, basically same alloy but without the tungsten. For reference, M4 martensite finish temperature is around -130°F.

 

[hugofeynman]

What's your opinion about those eta carbides? I haven't read a lot about those, does they benefit toughness?

Even if I have a lot of knives in pm steels, toughness for me comes first. In my friends opinion, Vanadis 4 extra is one of the toughest pm steels in existence, so I have most of my blades made of it. Of course I have also blades in low alloy steel, like k600, s1, 5160,....... but Vanadis 4 extra seems to have a great balance of toughness and edge holding.

 

[Willie71]

I don't know enough on the eta carbides to form an opinion. I've read that they increase toughness, and I've read that they decrease toughness. Once I dial in my HT with z-wear, I'll try with and without and test. I'm guessing I won't see a difference.

 

[shqxk]

From steel factory data seems like 400F tempering will get only below 60HRC on these steel while the high tempering will be able get to 63-66HRC.

I believe the amount of as quenched RA left on semi-high speed steel like V4E is too much to handle with cryo alone.

The 1000F tempering properly the only way to solve it and you get very high hardness as a bonus. Brad at Peters said V4E at 64HRC is tougher than M4 at 60RC and both steel were 1000F tempered.

 

[hugofeynman]

I don't know enough on the eta carbides to form an opinion. I've read that they increase toughness, and I've read that they decrease toughness. Once I dial in my HT with z-wear, I'll try with and without and test. I'm guessing I won't see a difference.

I also read contradictory conclusions about eta carbides, like you. So let's wait for your tests!

Regarding tempering, better stay with 1000F temper, shqxk to avoid unwanted surprises. Vanadis 4 extra is like an HSS optimized to cold work, so RA may stabilize too fast that only high temper will deal with it.

Bring those tests, Willie71!

 

[samuraistuart]

From steel factory data seems like 400F tempering will get only below 60HRC on these steel while the high tempering will be able get to 63-66HRC.

I believe the amount of as quenched RA left on semi-high speed steel like V4E is too much to handle with cryo alone.

The 1000F tempering properly the only way to solve it and you get very high hardness as a bonus. Brad at Peters said V4E at 64HRC is tougher than M4 at 60RC and both steel were 1000F tempered.

With M4 having Mf at -130F, and V4e being very close in composition, basically the same steel without the W, I would think cryo (LN2) would take care of virtually all detectable RA.

 

[jdm61]

At Blade a few years back, i was looking at the HT charts that B-U had. I mentioned to the rep that according to their specs, it looked like Elmax required a cold treatment a few degrees colder, at least 20-25, than what dry ice and solvent would give you and he said that I was correct.

With the similarity in composition with z-wear/cru wear, I suspect it would need full cryo, not just sub zero to complete the conversion to martensite.

 

[jdm61]

And surface/sublimation temp of dry ice is like -109F.

With M4 having Mf at -130F, and V4e being very close in composition, basically the same steel without the W, I would think cryo (LN2) would take care of virtually all detectable RA.

 

[hugofeynman]

So in the lack of deep cryo, better trust on high temper (for Vanadis 4 extra), to avoid problems.

At Blade a few years back, i was looking at the HT charts that B-U had. I mentioned to the rep that according to their specs, it looked like Elmax required a cold treatment a few degrees colder, at least 20-25, than what dry ice and solvent would give you and he said that I was correct.

 

[Willie71]

So in the lack of deep cryo, better trust on high temper (for Vanadis 4 extra), to avoid problems.

I tried subzero (as part of quench) with z-wear, and my Rc#s came out 1-2 Rc points lower, showing less conversion. I'm no expert, and haven't got the equipment to look at the microstructures, but that is my best guess.

 

[ShannonSteelLabs]

Sent off my first 2 blades in Z-wear to peters heat treating. Having them harden to 61-62HRC. Very excited to see how it performs

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[Willie71]

Chuck sent me some cru-wear to test. It's the cast, not pm version. It comes out 1-2 Rc points lower than the z-wear using the same programming in the kiln. I'm finding austentizing temp differences of 25f equal about 1 Rc point.

So far not a single chipped or deformed edge in any of the z-wear test blades out there right now, so under normal use Rc63/64 is a very useable blade. I'm austenitizing at 1950f for kitchen knives, and 1925f for general use knives. Being cast, I'm making an assumption that the cru-wear will perform similarly with the same heat treat, but be a little softer. I'll know more as I put the cru-wear blades to use.

 

[BluntCut MetalWorks]

I bought a couple cru-wear(cast/ingot) bars from AKS. Made 2 test blades. Edges after tests (of 7" blade, 12" oal, cruwear vs m2)

*ignore lower half of cruwear (due to multiple deflected chops at the end of wood block).

* cruwear chips from too many repeated chops onto same area of rippled edge.

*cruwear: carbide & grain are more observable via eye-piece.

iirc: aust 1975F 45-60 minutes soak (over soak isn't an issue with my ht process) with cryo quench (2-5 minutes just to ensure blade equalize with LN2 temperature). peak hardness: 66.5-67rc.

On my next order, I might grab 1-2 bars of zwear for similar tests and compare. iirc (off brain rather than test log) zwear carbide dia(~2um) is a little larger than m4. That was the reason why I want to try cast/ingot version of cruwear. Results are excellent and as expected (at least for my ht process anyway).