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Thought it would be nice to update the community on the current happenings of Nitrogen steels In 2019.
I am a custom knife maker and I have been personally exploring, testing and utilizing these different nitrogen steels.
The list of Nitrogen steels has grown a bit
Cast ingot "blow by" 0.10-0.15% wt N
H1
4116n
14c28n
Nitro V
BD1N
PESR (Pressurized ESR) ~0.5%wt N
LC200N/Zfinit
PM Nitrided 0.9-1.8% wt N
Nitrobe77
Vanax 37/Superclean
Damasteel DC18N pattern with N11x core
NEW 2019 Vancron Superclean
Most of these steels considered Nitrogen steels don't really have a lot of Nitrogen.
Nitrogen works just like carbon but is not as soluble in the iron and has an affinity for the chromium.
0.10-0.15% is just "blow by" nitrogen over the melt if in cast ingot steels with chromium helping pull it in. Most of the benefits dissolve in solution giving only sight additions/advantages acting like a "carbon booster" for hardness and slight boost in corrosion resistance in some cases. 0.10-0.15%wt is the limit of nitrogen in the steel unless more exotic methods are used.
H1, BD1N, Nitro V, 14c28n, 4116N, etc
Even steels like S125v, S110v and S90V can have this amount of Nitrogen in them.
@nsm
This is due to being atomized with nitrogen gas when making the steel from melt to powder and the Chromium helping pull the Nitrogen in, however the benefits are mostly minuscule in those steels due to the low volume and presence of other alloys taking dominance in the structures formed with time and heat.
Makes one wonder, what IS a nitrogen steel.
To get the huge volume of ~0.5% in lc200n they have to pressurize the melt and pump it in using PESR
It's at that level nitrogen level and alloy balance we get Nitrogen dominant martensite rather than carbon rich martensite we see in the 0.10-0.15% wt range "Nitrogen" steels, However the nitrogen is not as effective as carbon in hardness which might give it a sweet spot in sharpening yet also cap the hardness especially when combined with other factors.
However, the Cr2N chromium nitrides are harder than the Cr7C3 chromium carbides.
LC200N happens to not fully dissolve the Cr2N leaving some behind to help boost wear resistance, yet LC200N is also basically capped at 59-60rc due to too much Cr in solution preventing higher matrix hardness when quenching and especially with vacuum furnace quenching speeds combined with softer Nitrogen martensite compared to Carbon rich martensite.
High Nitrogen steels are more prone to "de-nitriding" than carbon steels are to decarbing at Austenizing temps before quenching. Especially in vacuum without increased partial pressure of nitrogen added.
So it's hard to get in the steel and it's easy for it to leave
The Nitrided PM steels are the most expensive steels on the market because of an exotic step added.
A quick recap, all PM steels are made by atomizing the molten steel with inert gas (nitrogen/argon) from the molten melt to fine powder collected in a canister andthen re solidified with Hot Isostatic pressing and cut and rolled out to sheets.
Nitrogen steels have the powder Nitrided Before HIP.
They Nitride coat the powder in a vacuum which is a lot more difficult and expensive than it sounds.
After HIP it is rolled out to sheets like other Non PM and PM steels.
This is how they achieve the high volume of Nitrogen in the steel with Vanax, Vancron and Nitrobe77 that is not possible with the other methods.
Which is why Lc200N is caped at ~0.5%wt Nitrogen
Nitrobe77 has 0.9% wt N which it uses some of to make nitrogen martensite like lc200n. Some of that nitrogen total is locked up as Cr2N that dissolves at the temperatures N77 requires to harden. That nitrogen put in solution will become nitrogen martensite when quenched. The nitrogen that did not dissolve stayed behind in a nice, small compliment of Niobium rich nitrides (MN type/NbN) which don't dissolve in the Chromium and Austenite as readily as the Vanadium at the temperatures required to harden Hence why we have Nb dominant MN type. These Nitrides are just not at enough volume to make this steel a "rope killer"
The Nitrobe 77 is unique thanks to it's ability to get harder than the other Nitrogen martensite rich steels like Lc200n thanks to being designed for precipitation strengthening. Using liquid nitrogen cryogenics and multiple high tempers after quenching allows the steel to raise up in HRC each cycle after hardening thanks to converting retained austenite that didn't transform from quenching to hard martensite and also the nitrides precipitating from the martensite and coarsening to the necessary sizes to strengthen the steel to resist displacement and make up for the shrinking of martensite.
It is possibly the best sharpening steel in the world and can operate at 62-64rc, The Nitriding process combined with this chemistry and volume makes a fine structured steel. The wear resistance is not super high however.
Nitrobe77 is one of my favorite steels but unfortunately due to cost, difficulty making at the steel mill and it not being cost effective to heat treat mass production. It has finally been discontinued by Damasteel as of 2018, they kept it alive for a long while.
I feel Des Horn has done some amazing work with Nitrobe 77 and had helped the steel persist for a long time @Deshorn
The Vanax 37/Superclean
(used by Damasteel under the name "N11x" as the core steel for there "San Mai" damacus DC18N)
Vanax is most corrosion resistant steel thanks to the dynamics that allow most of that HUGE chromium content (18% total volume) to be IN solution(15-17%) with a boost of the nitrogen also strengthening the chromium oxide film. We also have higher wear resistance than Lc200n and N77 thanks to the large amount of Vanadium 3.50% and Nitrogen 1.55% (very high)
It creates a mix of nitrogen and carbon martensite.
With carbon being more dominant since most of the Nitrogen is locked up with the Vanadium.
Update 3/4/20 ** there are Complex Multi element Cr2N Chromium Nitrides "M2N" present in the steel after HT. 10% M2N and 4% MN type Vanadium Nitrides. Updated from recent EDS and ThremoCalc work by PhD Larrin Thomas.
Vanax enough nitride volume to boost the wear resistance to S30V/ Elmax levels versus LC200N and Nitrobe77 being lower.
Because of the high amount of chromium in solution the Vanax is also basically capped at 59-60rc. Some heat treatments can boost to 61-62rc but perhaps not worth the effort and trade offs.
My current favorite,
Vancron Superclean is a Non stainless, Nitrided, A11 class, 10v type tool steel. with the carbon reduced and replaced with Nitrogen.
It has the highest amount of Nitrogen of the nitrogen steels at 1.8% wt N
It is the 2019 upgrade over Vancron 40/PUD 167 with the alloy composition redesigned to dissolve all the softer, larger M6C Moly/tungsten rich carbides like the ones found in CPM M4 and have it totally replaced with more of the finer, harder Vanadium Carbonitrdes.
The Chromium volume is low, it is not as stainless steel but designed to be a air hardening tool steel, so it will rust like 10v and K390 but we can also achieve insane matrix hardness 65+HRC since we are not being held back by Chromium in solution.
The martensite is carbon rich unlike LC200N and N77 thanks to the M6C and M23C6 carbides dissolving at lower temperature while austenizing. The nitrogen in Vancron is basically all going towards making Vanadium Nitrides which are not being dissolved and we have all the necessary carbon in solution from the carbides that did. We should also note that the remaining carbon not put in solution is also locked up in Vanadium carbides that are not dissolved just like the nitrides.
Hence why they are called Vanadium Carbonitrdes MX type with the "X" meaning either (C,N)
These Carbonitrdes are richer in Nitrogen however.
Carbonitride volume in the range between Vanadis 8 and K390/10v
The advantages to such an expensive steel is that the Carbonitrdes are much finer ranging at 1um at the largest down to submicron. While these Carbonitrdes are not as hard as pure MC type Vanadium carbides they offer a great sweet spot in between the second hardest carbides and the hardest MC type vanadium carbides.
So technically Vancron Superclean is not as wear resistant as 10v but wear resistance is only one piece of the puzzle.
The MX type Carbonitrdes are finer than carbides just like the nitrides in Vanax and Nitrobe77, this is not purely due to being nitrogen or volume but the Nitriding process forming the Nitrides at lower temps further preventing segregation. From my conversations with Larrin it sounds like if one could "graphize" a steel by adding carbon to an iron rich non carbon powder rich in carbide formers before HIP a simliar effect would happen.
So it's not just the inherit quality of nitrogen itself however nitrogen may provide a good sweet spot for sharpenablity. Currently there are no graphized pm steels available at this time and the cost would be even more insane.
The benefits to Vancron Superclean are that it has the finest carbides at high volume and it can create a very hard matrix making it perfect for thin ,wear resistant edges that will resist deforming yet have improved apex shaping also thanks to Carbonitrde size and Hardnesses compared to steels like 10v.
It's something of a perfect storm for 10-12 dps edges at under 0.010" bte and 65+ HRC for knives designed to cut.
It's the Geometry that does the cutting at the end of the day and the Vancron would provide more edge stability over 10v range steel. We shall see.
I'd like to thank PhD Larrin at "Knife Steel Nerds" for sharing in most of this information in articles and conversations.
His contributions and work are invaluable.
I have been knife testing and applying this knowledge first hand in my custom knife work.
Look forward to sharing more when time allows
BBB
Shawn
I am a custom knife maker and I have been personally exploring, testing and utilizing these different nitrogen steels.
The list of Nitrogen steels has grown a bit
Cast ingot "blow by" 0.10-0.15% wt N
H1
4116n
14c28n
Nitro V
BD1N
PESR (Pressurized ESR) ~0.5%wt N
LC200N/Zfinit
PM Nitrided 0.9-1.8% wt N
Nitrobe77
Vanax 37/Superclean
Damasteel DC18N pattern with N11x core
NEW 2019 Vancron Superclean
Most of these steels considered Nitrogen steels don't really have a lot of Nitrogen.
Nitrogen works just like carbon but is not as soluble in the iron and has an affinity for the chromium.
0.10-0.15% is just "blow by" nitrogen over the melt if in cast ingot steels with chromium helping pull it in. Most of the benefits dissolve in solution giving only sight additions/advantages acting like a "carbon booster" for hardness and slight boost in corrosion resistance in some cases. 0.10-0.15%wt is the limit of nitrogen in the steel unless more exotic methods are used.
H1, BD1N, Nitro V, 14c28n, 4116N, etc
Even steels like S125v, S110v and S90V can have this amount of Nitrogen in them.
@nsm
This is due to being atomized with nitrogen gas when making the steel from melt to powder and the Chromium helping pull the Nitrogen in, however the benefits are mostly minuscule in those steels due to the low volume and presence of other alloys taking dominance in the structures formed with time and heat.
Makes one wonder, what IS a nitrogen steel.
To get the huge volume of ~0.5% in lc200n they have to pressurize the melt and pump it in using PESR
It's at that level nitrogen level and alloy balance we get Nitrogen dominant martensite rather than carbon rich martensite we see in the 0.10-0.15% wt range "Nitrogen" steels, However the nitrogen is not as effective as carbon in hardness which might give it a sweet spot in sharpening yet also cap the hardness especially when combined with other factors.
However, the Cr2N chromium nitrides are harder than the Cr7C3 chromium carbides.
LC200N happens to not fully dissolve the Cr2N leaving some behind to help boost wear resistance, yet LC200N is also basically capped at 59-60rc due to too much Cr in solution preventing higher matrix hardness when quenching and especially with vacuum furnace quenching speeds combined with softer Nitrogen martensite compared to Carbon rich martensite.
High Nitrogen steels are more prone to "de-nitriding" than carbon steels are to decarbing at Austenizing temps before quenching. Especially in vacuum without increased partial pressure of nitrogen added.
So it's hard to get in the steel and it's easy for it to leave
The Nitrided PM steels are the most expensive steels on the market because of an exotic step added.
A quick recap, all PM steels are made by atomizing the molten steel with inert gas (nitrogen/argon) from the molten melt to fine powder collected in a canister andthen re solidified with Hot Isostatic pressing and cut and rolled out to sheets.
Nitrogen steels have the powder Nitrided Before HIP.
They Nitride coat the powder in a vacuum which is a lot more difficult and expensive than it sounds.
After HIP it is rolled out to sheets like other Non PM and PM steels.
This is how they achieve the high volume of Nitrogen in the steel with Vanax, Vancron and Nitrobe77 that is not possible with the other methods.
Which is why Lc200N is caped at ~0.5%wt Nitrogen
Nitrobe77 has 0.9% wt N which it uses some of to make nitrogen martensite like lc200n. Some of that nitrogen total is locked up as Cr2N that dissolves at the temperatures N77 requires to harden. That nitrogen put in solution will become nitrogen martensite when quenched. The nitrogen that did not dissolve stayed behind in a nice, small compliment of Niobium rich nitrides (MN type/NbN) which don't dissolve in the Chromium and Austenite as readily as the Vanadium at the temperatures required to harden Hence why we have Nb dominant MN type. These Nitrides are just not at enough volume to make this steel a "rope killer"
The Nitrobe 77 is unique thanks to it's ability to get harder than the other Nitrogen martensite rich steels like Lc200n thanks to being designed for precipitation strengthening. Using liquid nitrogen cryogenics and multiple high tempers after quenching allows the steel to raise up in HRC each cycle after hardening thanks to converting retained austenite that didn't transform from quenching to hard martensite and also the nitrides precipitating from the martensite and coarsening to the necessary sizes to strengthen the steel to resist displacement and make up for the shrinking of martensite.
It is possibly the best sharpening steel in the world and can operate at 62-64rc, The Nitriding process combined with this chemistry and volume makes a fine structured steel. The wear resistance is not super high however.
Nitrobe77 is one of my favorite steels but unfortunately due to cost, difficulty making at the steel mill and it not being cost effective to heat treat mass production. It has finally been discontinued by Damasteel as of 2018, they kept it alive for a long while.
I feel Des Horn has done some amazing work with Nitrobe 77 and had helped the steel persist for a long time @Deshorn
The Vanax 37/Superclean
(used by Damasteel under the name "N11x" as the core steel for there "San Mai" damacus DC18N)
Vanax is most corrosion resistant steel thanks to the dynamics that allow most of that HUGE chromium content (18% total volume) to be IN solution(15-17%) with a boost of the nitrogen also strengthening the chromium oxide film. We also have higher wear resistance than Lc200n and N77 thanks to the large amount of Vanadium 3.50% and Nitrogen 1.55% (very high)
It creates a mix of nitrogen and carbon martensite.
With carbon being more dominant since most of the Nitrogen is locked up with the Vanadium.
Update 3/4/20 ** there are Complex Multi element Cr2N Chromium Nitrides "M2N" present in the steel after HT. 10% M2N and 4% MN type Vanadium Nitrides. Updated from recent EDS and ThremoCalc work by PhD Larrin Thomas.
Vanax enough nitride volume to boost the wear resistance to S30V/ Elmax levels versus LC200N and Nitrobe77 being lower.
Because of the high amount of chromium in solution the Vanax is also basically capped at 59-60rc. Some heat treatments can boost to 61-62rc but perhaps not worth the effort and trade offs.
My current favorite,
Vancron Superclean is a Non stainless, Nitrided, A11 class, 10v type tool steel. with the carbon reduced and replaced with Nitrogen.
It has the highest amount of Nitrogen of the nitrogen steels at 1.8% wt N
It is the 2019 upgrade over Vancron 40/PUD 167 with the alloy composition redesigned to dissolve all the softer, larger M6C Moly/tungsten rich carbides like the ones found in CPM M4 and have it totally replaced with more of the finer, harder Vanadium Carbonitrdes.
The Chromium volume is low, it is not as stainless steel but designed to be a air hardening tool steel, so it will rust like 10v and K390 but we can also achieve insane matrix hardness 65+HRC since we are not being held back by Chromium in solution.
The martensite is carbon rich unlike LC200N and N77 thanks to the M6C and M23C6 carbides dissolving at lower temperature while austenizing. The nitrogen in Vancron is basically all going towards making Vanadium Nitrides which are not being dissolved and we have all the necessary carbon in solution from the carbides that did. We should also note that the remaining carbon not put in solution is also locked up in Vanadium carbides that are not dissolved just like the nitrides.
Hence why they are called Vanadium Carbonitrdes MX type with the "X" meaning either (C,N)
These Carbonitrdes are richer in Nitrogen however.
Carbonitride volume in the range between Vanadis 8 and K390/10v
The advantages to such an expensive steel is that the Carbonitrdes are much finer ranging at 1um at the largest down to submicron. While these Carbonitrdes are not as hard as pure MC type Vanadium carbides they offer a great sweet spot in between the second hardest carbides and the hardest MC type vanadium carbides.
So technically Vancron Superclean is not as wear resistant as 10v but wear resistance is only one piece of the puzzle.
The MX type Carbonitrdes are finer than carbides just like the nitrides in Vanax and Nitrobe77, this is not purely due to being nitrogen or volume but the Nitriding process forming the Nitrides at lower temps further preventing segregation. From my conversations with Larrin it sounds like if one could "graphize" a steel by adding carbon to an iron rich non carbon powder rich in carbide formers before HIP a simliar effect would happen.
So it's not just the inherit quality of nitrogen itself however nitrogen may provide a good sweet spot for sharpenablity. Currently there are no graphized pm steels available at this time and the cost would be even more insane.
The benefits to Vancron Superclean are that it has the finest carbides at high volume and it can create a very hard matrix making it perfect for thin ,wear resistant edges that will resist deforming yet have improved apex shaping also thanks to Carbonitrde size and Hardnesses compared to steels like 10v.
It's something of a perfect storm for 10-12 dps edges at under 0.010" bte and 65+ HRC for knives designed to cut.
It's the Geometry that does the cutting at the end of the day and the Vancron would provide more edge stability over 10v range steel. We shall see.
I'd like to thank PhD Larrin at "Knife Steel Nerds" for sharing in most of this information in articles and conversations.
His contributions and work are invaluable.
I have been knife testing and applying this knowledge first hand in my custom knife work.
Look forward to sharing more when time allows
BBB
Shawn
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