420 HC v. 440 C

[mp510]

Guys, I am trying to figure a couple of things out. What is the average hardness of a 440 C blade?

I presume that 440 C is preferable over 420 HC, correct?

I come to this assumption, since I believe that the higher carbon content would provide better edge retention. However, what impact would the lack of vandium in 440 C (there is .18 in 420 HC) have on the blade? I do know that 440 C has more molybendum than the 420 HC?

I found this interesting, because my Buck 373, which is a value line knife, seems to have a higher grade steel than the high end counterpart, the 301. Was I correct in my thinking?

 

[Boats]

My take:

420HC is the minimally acceptable stainless to me. The "HC" is the only thing saving it from being no better than liner material rather than blade steel. Regular 420 is too soft, so the extra carbon in 420HC (0.44% as opposed to 0.15-0.38 for regular 420) gives it barely reasonable toughness, wear resistance, while retaining good anti-corrosion properties.

440C is the queen bee of the 400 series stainless steels used in knife making. It features carbon in the 0.95 to 1.2% range. The higher carbon content making for a generally tougher and better wearing blade is really the main difference between the two. The other is that 440C isn't quite as corrision resistant as the 420HC, but still excellent.

Both steels are generally hardened to 57-59 RC. It is not the hardness on the Rockwell scale that is the difference between the two, but rather their differing chemical compositions giving them different properties. However, Buck is known to take their 420HC up to 60-61, which would definitely help its wear resistance and allow for better edge retention, but at the expense of being more brittle against lateral forces. I could see why Buck might put an extra hard 420HC blade on a knife rather than 440C. In most cases, from most makers, if those are my choices, I am going with 440C usually. Paul Boz having been long involved in Buck's heat treating process is why they are the only maker using 420HC that I would trust without much reservation.

The vanadium in 420HC helps its grain structure and malleability under heat. It might also be considered to help its wear resistance some.

The molybdenum in 440C assists in its hardenability.

Both elements are nice to have in a stainless steel. Neither is present in enough quantity in the steels we are discussing to be so-called "super stainlesses" like VG-10 or S30V for instance.

I keep it easy on myself. I don't generally buy any new stainless steel knives. D2 tool steel, a so-called semi-stainless, is as close as I get. I do have some Buck 110s in 420HC kicking around the place for sentimental reasons though.

 

[hso]

I presume that 440 C is preferable over 420 HC, correct?

No, not actually. The 420 HC is a very good corrosion resistant steel and has a good balance between toughness and hardening ability (remember the H in HC stands for high carbon). 440C is focused on rust resistance and produces a hardenable blade with not so good toughness. 420 HC can be hardened to RC 58.

440C can be hardened in a wide range depending upon the intended use. RC 56-58 is common, but harder small blades are commonly made.

 

[Rupestris]

Boats,
Great info. If I could tack another question onto this thread...
You mentioned D2. I don't own any D2 blades yet but I do have a BRKT that is A2 tool. Whatd the dif there?

Personally, I have never had a problem using pocket folders of 440C. Now that Benchmade offers the Mini Griptilian in D2, I'm thinking about trading up.

thanks

 

[Boats]

Coincidentally, I have three Bark River Gameskeepers and a couple of Mini-Canadians, all in A2 steel. They are my only exposure to that steel as Chris Reeves and Mission Knives are the only other makers I know of who use it on a production basis.

I like A2's ability to take and hold an edge. Bark River has done an excellent job in making A2 perform like a laser. They are uniformally the sharpest knives I have ever used or seen. In the field though, A2 has to be watched for the formation of rust and it takes a patina easily, which bothers some, but not me.

All of my D2 is from Benchmade. I have two 806D2 Axis folders and a just acquired 156 CSK fixed blade. I like D2 for its ability to hold an edge even better than A2, but it is not as easy to sharpen to a wicked level. I also tend to believe, from my experience, that the A2 edge is a little less brittle than a D2's edge as A2 seems to deform rather than chip.

I long ago stripped the beat up coating off of one of my AFCKs and corrosion and staining has not been a serious concern with bare D2, but it doesn't look as nice in the white as A2 does, a dull matte grey being about as good as it gets with reasonable hand sanding. D2's seeming inability to easily take on a satin finished look is part of the reason I think it gets coated.

One thing that makes it difficult for me to compare the steels is the convex grinds on the BRKT knives. That grind creates what is essentially a zero degree edge, which make most cutting comparisons to more conventionally ground knives rather unfair.

 

[XLMiguel]

FWIW, Bladeforums.com has a pretty good primer on blade steels in their library, IIRC -