Both Nitrobe and Vanax won't ever have Carbides of any kind, just nitrides. M2N nitrides or MN nitrides, but nitrides.
From the link i posted above
"The microstructure and hardness in the hardened and tempered condition for the steels are shown in Fig. 2.
All grades have a tempered martensitic matrix with various amount and type of hard phases. The size of
the hard phase particles is around 50% bigger in carbon based PM steels compared with MN particles in
the nitrogen alloyed PM grades. In absolute values an average size of the MN particles is around 0,7 μm in
the heat treated condition. The conventionally ingot manufactured grade, AISI D2 and AISI 440B/C, may
have maximum carbide sizes up to 100-200 μm depending of ingot size and hot working reduction."
Please, read that very informative document, as it contains also very useful info for steels other than nitrogen ones.
JMAW is Just Might As Well.
Elmax has been mentioned by me as it is an exception under many aspects, in the non nitrogen based highly alloyed stainless steels. It has a very high content of Cr M7C3 carbides, a very high amount of carbon, Cr content is no candy either. You would expect SEVERE chipping problems, even more severe than in S30V. Right?
Wrong, as their PM process has done the miracle (very clean and very uniform structure): this is the only stainless steel that using secondary hardness reaches 43J@63HRC. Thus no chipping issue. It is the value CPM-M4 @62.5 reaches, but without added benefit of stain resistance.
Yet using the HT mentioned in the document, with deep cryo, you would have quite more stain resistance, with a 40J value, roughly as stain resistant as 440C yet with the double the edge retention. Many production makers have got the point and a Kershaw Speedform II will be the clear example of an EDC at affordable prices, made out of Elmax and with more than decent stain resistance, excellent toughness (comparable or Greater than many tool steels).
S60V is quite another story than Elmax. Taken at 60HRC it was chipping. Thus the general consensus switched to a ridicolous 56HRC value. A that point edge rolling, gummy edge and alike made Crucible think that a new steel should have been introduced. That was CPM 420V AKA CPM S90V. When properly heat treated even without being a toughness champion it performed better. Yet it was a pain to HT and grind and sharpen.
So CPM S30V was thrown out, for better workability and toughness, with all makers agreeing on the 58-60 range (not Chris Reeve). This proved to be underhardening and thus gummy edge, edge rolling... Crucible came out with CPM-154 and S35VN, which again were not a quantum leap forward their predecessors and S110V, which can be a very good steel, but with very limited toughness that will limit its using environment.
Notably, about S90V it is Worth mentioning the opinion of Elliot Williamson, reknown custom maker and friend of mine:
"S90V is finally getting a little more use in the custom knife world and with some good reason. It does make very good knives that hold edges very well. It does have a reputation for micro-chipping like it's little brother S30V and I have seen this now in some of the knives I've used this steel in. I haven't had happen to me during any testing, but those are tests and not real world use. The culprit in this micro-chipping issue is most likely because most knife makers use a standard tempering heat treatment which converts retained Austenite to Cementite in the Martensite plate boundaries, which is pretty normal, but because it has some much carbon you are getting too much Pearlite in the Cementite and it has too low a bond potential to resist shears that would not be an issue in steels with less carbon. I think the fix is going to be using a the secondary hardening phase and let that over saturation of carbon get locked up in carbides and thus increase the bond potential in the plate boundaries."
Roughly said 1180°C (2155°F) + 450°C (842°F)/2x2h with 60HRC, 11.4% Cr in solid solution.
As a comparison Elmax 1080°C (1975°F) + 200°C (392°F)/2x2h 59 HRC (Deep cryo adds 1-2HRC), 12% Cr in solid solution.
I have no such data for M390, another steel cited here by other mates. but has less toughness than Elmax (it should be in the 35J range), requires more attention (nu foil and other) and care in HT and slightly higher austenitizing and tempering temperature. I.e.: 1150°C/200°C-260°C per Bohler data (60-62HRC with mandatory sub-zero treatment).
I can make an educated guess that it will have 13% Cr in solid solution with this HT and 4-5% V based MC type carbides.
I've had corrosion issues with H-1 in the environment I mentioned above. I had with 14C28N, N680, Niolox as well.
Nitrobe 77 and Vanax just belong to another level, with the latter holding an advantage in anything but toughness.
Thanks for the HT table for Nitrobe 77
But it requires insanely complicated HT. With very high austenitizing/tempering temps. Do a cross check with the specs for Vanax in the above mentioned link.
My understanding is that to overcome less than optimal (for knife use) edge holding, the HT has been tuned to increase hardness. IMHO this way the amount of Cr in solid solution is not maximized, deteriorating both corrosion resistance and toughness. Probably 1050°C/deep cryo/200°Cx2 2hrs each would be better, loosing a couple of HRC points.
Finally.
I mentioned some carbon steels as well.
Limiting to one of them, CPM-3V is a very cleverly engineered steel. If kept 57-59HRC all of Cr and Moly will be used to stain resistance purpose because there will be only V MC carbides (5%). Making reference to the link I posted, if D2 has a PRE value of 8, having 3V 7.5%Cr and 1.3%Mo and given that
"The PRE number is
the sum in weight percent of the following elements in solid solution Cr+3,3Mo+16N", the PRE number for CPM-3V should be (7.5+(3*1.3))=10.4. Higher than D2 which is considered as being semi-stainless and thus we could fairly use CPM-3V for tasks where extreme toughness and very good edge holding are the requisites, with decent stain resistance. In my experience I've seen ZDP189, ATS34, CM154 and 440C staining before CPM-3V, given the same level of finishing and without any coating or manteinance.
I hope to have answered all of your questions.
You're right about the origin of Nitrobe and Vanax. Also S30V has been created for knives, but we know that it ain't properly the best choice out there
And agreed about the gratefulness we owe to Crucible, Bohler, and all of the steel makers that allowed all of that to all us knifenuts.
Maybe he hates me for that...
