corrosion resistance of CPM M4

M

mdoyle

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Feb 10, 2006
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Hi,
Have a customer wanting an identical matched set,(Father and Son) of hunting knives. His description of wants was great edge holding and good toughness, with at least fair corrosion resistance. I was thinking about CPM M4...Great wear resistance, great toughness, but what about the corrosion resistance?
Here are the specs listed on crucible's site:

Carbon 1.42%
Chromium 4.00%
Vanadium 4.00%
Tungsten 5.50%
Molybdenum 5.25%
Manganese 0.30% (0.70%)
Sulfur* 0.06% (0.22%)
Anyone have any experience with it? Would it hold up to a bead blasted finish, or would that just be asking for trouble...

Thank you in advance,
Matt Doyle
 
me i like 3V
7.5% chrom

i dont know for sure how M4 holds up to rust but i hear tht in edge holdign its way way up there
like use DMT stones or good belts on a grinder to sharpen
 
Loyd
I considered 3v, but in comparing the two, CPM3v has far superior toughness, and the CPM M4 has far superior wear resisitance, and still more toughnes than almost any other knife steels that we consider to be tough. Aside from your 3V of course:D Not arguing of course, just still kicking it around in my head.:D
Matt
 
yep understand


one of these days i ll be able to tell you first hand how i like M4 as i plan on tring it out
so far as rust as long as there kept up with there should not be an issue

i dont think i would bead blast tho as that lets water get a "grip/stick" to the blade a belt finish thats buffed would be the choice as hand sanding im told sucks on M4 if its anything like cpm10v
than you can bet i would charge 2x more for the hand sanded finish
 
A customer of mine bought some knives in M4 from me. He says he uses one of them regularly, and hasn't sharpened it since he got it, which was last spring or summer, I think. :eek: Just make sure you do all the polishing before heat treating.... :D
 
Most of the air hardening grades have a certain amount of corrosion resistance, and M4 is air hardening. Those that claim that low alloy steels like 5160 have more corrosion resistance than 1060 are splitting hairs, they're nearly identical. You can always test a knife out to see.
 
from the december issue of blade "maintain M4 like you would and carbon or tool steel.be sure you wipe any fingerprints off the blade. " sounds like a great choice for a hunter if you go by what the rest of the article edge holding is supposed to be awesome just hold down the hardness to 59 to 61 RC .but thats all hearsay .
 
Well CPM-M4 has all the characteristics to be a good edge holder: high edge stability, toughness, small carbide size, high wear resistance, etc. It has a very nice set of properties.
 
If we could leave some CPM-M4 and some CPM-MPL1 in a dark room with a bottle of vodka we might get the ultimate blade steel as the offspring.
Stacy
 
bladsmth said:
If we could leave some CPM-M4 and some CPM-MPL1 in a dark room with a bottle of vodka we might get the ultimate blade steel as the offspring.
Stacy
Click to expand...

Stacy
Very true but we would have to personally inspect the dark room for potential mixers to ensure that nothing foreign entered the mix.....
Matt
 
I have seen M4 tool bit rust like crazy. Not enough chromium to really make a difference. But then had some rusty ATS34 too. Not much is immune.
 
dear god that looks alot like the cpms125v i have and im not looking forward to that long hour blade

i ll ask about it any how on my next order
 
A C Richards said:
I have seen M4 tool bit rust like crazy. Not enough chromium to really make a difference. But then had some rusty ATS34 too. Not much is immune.
Click to expand...
It will definitely rust, but I will argue with you that it doesn't have enough chromium to make a difference, it definitely has enough chromium to have better corrosion resistance than 1095.
 
Sure it has more corrosion resistance than 1095. It does not make that much difference though. D2 will rust really fast if it is not taken care of and it has 12% chromium. I had a bucket full of old knife blades that had been scraped for one reason or another. Included A2 D2 ATS43 1095 cable damascus etc. After about a month you could not tell the difference from one steel to the next. Unfortunately some rely on the corrosion resistant properties of steel rather than takeing care of the knife. I have had very few problems with straight carbon steel because i take care of them. I would treat M4 just like any carbon steel blade and not rely on the chromium to do the job I am supposed to do.
 
Chuck
Very good point. I will keep that thought close for my conversation with the customer. Thanks for all your help guys! I'm Pretty sure I can talk Loyd into grinding some CPM-MPL1 for me.:D He's a sucker for a challenge...Those are the easiest folks to trick!:D:D
Matt
 
i still need to get to the s125v bar that i have in house to try im sure phill is wanting to here me curse it too
 
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