Tungsten Carbide in Crucible Steel

[2red4U]

I have a CPM-S35VN Keizer knife that I believe has Tungsten in it.

It seem like it would be a good compound to have in a knife blade and doesn't seem like manufactures make it much. Is sharpening the main issue with a blade like that?

 

[tiguy7]

CPM S-35-VN has 0.40%Tungsten in it, but the Tungsten Carbide at 72HRC is not as much of an impediment to sharpening as the 3.00% included Vanadium Carbide at 82 HRC.

 

[Alberta Ed]

Tungsten adds strength, toughness and improves hardenability, according to Spyderco. Download Spyderco's current catalogue; there is an excellent section on steels.

 

[2red4U]

Thanks guys. Yea its my experience with Tungsten Carbide with cutting tools made me think of the importance of it in a knife.
Looks like Vanadium Carbide is what they incorporate for edge retention, as with the newer S110V (score 10 out of 10 for edge retention).

I have not tried sharpening my knife yet, not exactly looking forward to that.

 

[dkb45]

There's steels with enough tungsten to form carbides, but S35VN is not one of them. I don't think Super Blue has enough to form carbides, with up to 2%. I believe the problem with tungsten is that it is fickle on the heat treat, and forms large and hard carbides. There are people who know a lot more, though.

 

[Larrin]

The Zknives steeel database incorrectly lists the tungsten content of S35VN as 0.4%. S35VN doesn't have a tungsten addition.

There are many steels with high tungsten additions to them, in the range of 5-18% in high speed steels, and many of those are used in knives (Maxamet, M2, M4, Rex 121, Hap 40, etc.). With high speed steels the tungsten does not form the very hard tungsten monocarbide (WC), instead they form a much softer W6C. In low alloy tungsten steels like Blue Super, F2, 1.2562, 1.2519, O7, V-Toku they actually do form some WC. With a significant chromium addition (>3%) as in the high speed steels they form the softer carbide.

 

[dkb45]

The Zknives steeel database incorrectly lists the tungsten content of S35VN as 0.4%. S35VN doesn't have a tungsten addition.

There are many steels with high tungsten additions to them, in the range of 5-18% in high speed steels, and many of those are used in knives (Maxamet, M2, M4, Rex 121, Hap 40, etc.). With high speed steels the tungsten does not form the very hard tungsten monocarbide (WC), instead they form a much softer W6C. In low alloy tungsten steels like Blue Super, F2, 1.2562, 1.2519, O7, V-Toku they actually do form some WC. With a significant chromium addition (>3%) as in the high speed steels they form the softer carbide.

I was hoping you would chime in with the facts. Tungsten seems to work counter to how I thought, I figured that lower percentage steels like Super Blue would use tungsten as a refining element and not a secondary carbide former. I also thought that high tungsten steels, like Maxamet or T15, would have tungsten carbide as a secondary or tertiary carbide former, competing with vanadium (because it seems almost every high tungsten steels also has moderately high vanadium, I'm sure there's a reason why.)

 

[Larrin]

Vanadium is just the element they use to give the steel more wear resistance since the Mo/W6C carbides aren’t as hard as the VC. The W and Mo is added for hot hardness.

 

[ferider]

Love those two from Spyderco and the similar high HRC (> 66). Rex45 has noticeably less wear resistance, but is tougher; I don't mind sharpening for either, it's easier for me than - say - M390. I've broken a Spyderco Maxamet Gen1 blade, eager to try the new incarnation in the PM2.

I thought the Co was for hot hardness, but I'm not an expert.

 

[Alberta Ed]

Thanks guys. Yea its my experience with Tungsten Carbide with cutting tools made me think of the importance of it in a knife.
Looks like Vanadium Carbide is what they incorporate for edge retention, as with the newer S110V (score 10 out of 10 for edge retention).

I have not tried sharpening my knife yet, not exactly looking forward to that.

I've found S100V sharpens fairly easily starting with a DMT extra-coarse (220 grit) followed by a few finishing strokes on a DMT ultra-fine (1200 grit).

 

[DeadboxHero]

The Zknives steeel database incorrectly lists the tungsten content of S35VN as 0.4%. S35VN doesn't have a tungsten addition.

There are many steels with high tungsten additions to them, in the range of 5-18% in high speed steels, and many of those are used in knives (Maxamet, M2, M4, Rex 121, Hap 40, etc.). With high speed steels the tungsten does not form the very hard tungsten monocarbide (WC), instead they form a much softer W6C. In low alloy tungsten steels like Blue Super, F2, 1.2562, 1.2519, O7, V-Toku they actually do form some WC. With a significant chromium addition (>3%) as in the high speed steels they form the softer carbide.

So nice having a Metallurgist around.

Love those two from Spyderco and the similar high HRC (> 66). Rex45 has noticeably less wear resistance, but is tougher; I don't mind sharpening for either, it's easier for me than - say - M390. I've broken a Spyderco Maxamet Gen1 blade, eager to try the new incarnation in the PM2.

I thought the Co was for hot hardness, but I'm not an expert.

The Co, W and Mo work together for Hot Hardness but the Co is not a carbide former, it's does something different.

Larrin touched on the topic in his VG10 article. It's has to do with what happens to the steel when being tempered but one has to learn what makes steel hard to begin with and than one can understand the role of Cobalt more and it's effect when tempering and secondary carbides. It's all on Larrin's website.