New Steel Analysis – Damasteel N11X and Damacore DC18N

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N11X and Damacore DC18N

Last month I released an article about nitrogen-alloyed knife steels. After I posted the article I was informed about a new Damasteel product that includes a nitrogen-alloyed stainless steel as the core in a san-mai damascus steel product. At the time there was no information on the core steel other than its name: Damacore DC18N refers to a product with a core of “N11X” nitrogen steel and has san-mai damascus sides of RWL34 and PMC27 (their standard damascus mix without a core steel). Damasteel has recently released a datasheet for the new product which has provided more information: http://damasteel.se/wp-content/uploads/2018/06/Data-Sheet-Martensitic-Damacore-Final-Version.pdf

This image taken from [1]

I at first assumed that they would be using Nitrobe77 in some fashion since that is a nitrogen-alloyed steel that they have been selling that as a monosteel for a little while now. However, they use a different name for the core steel: N11X. A different steel produced by Erasteel? A modification of Nitrobe77? The datasheet gives the composition for the core steel as the following:

Is it Vanax?

I thought that the composition of N11X looked remarkably similar to Uddeholm Vanax, and comparison with the Vanax datasheet [2] confirms that it is in fact identical:

Are they using Uddeholm Vanax or is the steel produced by Erasteel (a frequent partner of theirs) under license? I emailed Damasteel and Per Jarbelius sent some interesting information about the development of the steel as well as more history of nitrogen-alloyed steel development in Sweden. He stated, “N11X™ has similar composition to Vanax® SuperClean and is used by the permission of Uddeholm. The Damacore® DC18N™ is an all powder metallurgy made steel.” You can read the full statement from Per at this link here: Damacore Background. He also sent a copy of the PowerPoint presentation given at Blade Show West about the new product which you can see here: Damacore PowerPoint. In his email to me, Per said, “The main thing I want to stress is that the development of the Damacore was first initiated by the knife making community who asked for a high-quality product from Damasteel. The challenge of achieving this was substantial since we wanted to stick to our trademark being all powder metallurgy made. We also wanted to achieve a product that was aesthetically appealing and carrying the recognition of being Damasteel.” 

This image taken from [4]

Properties of N11X

Since N11X should have the same properties as Vanax, it makes sense to discuss what we know about Vanax. I wrote some about Vanax in the article about nitrogen-alloyed steels. It is the most wear resistant of the currently available nitrogen-alloyed stainless steels because of its relatively high fraction (13%) of vanadium nitrides which are reported to be as hard as vanadium carbides [5]. The high hardness of vanadium carbides is what gives steels like 10V and S90V their very high wear resistance. Vanax is also reported to have superior toughness to Elmax [2], a steel which Bohler-Uddeholm claims is tougher than many other stainless steels [6]. 

N11X vs RWL34/PMC27

While using a san-mai damascus product can provide a a different aesthetic vs conventional Damascus, some will be selecting Damacore DC18N based on the performance differences relative to the typical DS93X made from RWL34 and PMC27. Therefore I will provide some speculation on the performance differences between DS93X and DC18N.

Corrosion Resistance

N11X likely has superior corrosion resistance to RWL34 and PMC27. For example in Erasteel’s patent for the nitrogen steel PUD 177.0 which is sold by Damasteel as Nitrobe77, they make a direct corrosion resistance comparison with RWL34 [7]. In a test in “chloride-containing water,” they found staining with RWL34 but not with Nitrobe77. RWL34 uses a high molybdenum content to make up for relatively low chromium in solution for adequate corrosion resistance [8][9], but it is not at the level of Nitrobe77 or Vanax. N11X therefore likely has less sharpness loss than RWL34/PMC27 when cutting in corrosive environments or cutting corrosive materials. 

Slicing Edge Retention

We tested the damascus combination AEB-L/154CM with the CATRA edge retention tester. AEB-L is quite similar to PMC27 and RWL34 is famously based on 154CM and ATS-34. AEB-L with its small volume of chromium carbides (~6%) is much less wear resistant than 154CM (~17.5%) and when combined in a 50:50 mix the AEB-L/154CM damascus was right in between the two steels. If we call AEB-L a “low” wear resistance steel and 154CM a “medium” wear resistance steel, relative to high wear resistance steels like S90V, then AEB-L/154CM and therefore RWL34/PMC27 would be a “medium-low” wear resistance steel. In slicing edge retention it would be a “medium-low” edge retention steel. N11X would likely be an upgrade in slicing edge retention with its 13% vanadium nitride. I can’t predict exactly what the edge retention difference would be but I estimate the edge retention of N11X as roughly 40-80% better than RWL34/PMC27. I don’t know what the exact mix is between RWL34 and PMC27 in Damasteel which also makes estimates difficult. 

Toughness

We have tested the toughness of AEB-L and CPM-154 among others as shown above. CPM-154 has good toughness and RWL34 is likely similar. AEB-L is the toughest steel we have yet tested which should be similar to PMC27. How the damascus combination ends up for toughness is a bit tough to predict and likely depends on the type of toughness test used. For some tests it is limited by the “weakest link” meaning that the steel would trend closer to CPM-154 than halfway in between in a 50:50 mix. So the best case scenario is halfway between PMC27 and RWL34 and worst case is equal to RWL34. 154CM has been reported to have 17.5% carbide volume [10] and Elmax has been reported to have 18% carbide volume [11] after heat treatment. This is significant because toughness in these steels is largely controlled by their carbide volume and Vanax toughness has been compared to Elmax. RWL34 and Elmax are expected to have similar toughness because of their similar carbide volume. Uddeholm reports that Vanax has approximately 30% greater toughness than Elmax [2], and therefore likely has approximately 30% greater toughness than RWL34. So I think in general we can say that N11X has roughly similar toughness to RWL34/PMC27 damascus steel. 

Hardness

RWL34 has relatively good hardness potential, reaching as high as 64 Rc with a 2010°F (1100°C) austenitize, deep freeze, and 345°F (175°C) temper [12]. PMC27 does not reach the same level of hardness, achieving 60 Rc with the same heat treatment [12]. Uddeholm recommends a heat treatment for Vanax of 1975°F (1080°C), deep freeze, and 390°F (200°C) temper for a hardness of 59-60 Rc [2]. The same heat treatment with RWL34  yields about 60.5 Rc and with PMC27 57 Rc. Therefore the potential hardness of N11X is about 1 Rc lower than RWL34 but 2.5 Rc higher than PMC27. 

San-Mai Damascus

It requires some development work to design a new damascus product, in this case the DC18N which includes not just the N11X core but also the laminated damascus “sides” of the san-mai damascus. They chose to use their standard mix of RWL34 and PMC27 for the damascus part of the san-mai. Selecting steels for damascus and san-mai is not trivial because the steels must be compatible in several ways, including:

1. Austenitizing (hardening) and tempering temperatures must be similar so that adequate hardness, toughness, and corrosion resistance is achieved for all three steels
2. The size changes that occur during heat treatment must be sufficiently compatible that splitting does not regularly occur
3. Good contrast after etching must be possible

In the PowerPoint presentation on Damacore DC18N it states that a new manufacturing process was developed for “centering the core.” In san-mai damascus keeping the core steel centered and even is difficult and when poorly done it results in uneven pattern distribution in finished blades. In the available photos of knives made with DC18N it does indeed appear that the core steel is well-centered.

Using their standard mix of RWL34 and PMC27 means that they can use steel they already own and are familiar with. It also means that current customers of Damasteel can use the same etching procedure they already use for the standard Damasteel product. The use of the N11X core provides superior slicing edge retention, while retaining similar hardness and toughness. In other ways the choice of RWL34/PMC27 is odd. For one thing, a major benefit of using nitrogen-alloyed steel is the superior corrosion resistance. However, RWL34 and PMC27 are not known for having particularly great corrosion resistance. Therefore they have laminated a core steel known for its very high corrosion resistance with steels that are more susceptible to corrosion. Meaning that pitting or rusting of the damascus sides may occur if the steel is used in corrosive environments where N11X excels. Perhaps one might argue that people are not generally using knives with expensive Damascus steel in seawater. It would be a little more exciting to see Damasteel use high corrosion resistance steels for the damascus sides or even a mix with all nitrogen-alloyed steels. 

This image from [13]

Summary

Damacore DC18N is an interesting product in that it is using a relatively high wear resistance core steel with san-mai damascus sides. This is not the first occurrence of damascus steel laminated over a wear resistant core steel, but perhaps the first Damascus product to use a high-nitrogen steel in the core. The N11X core provides superior slicing edge retention to RWL34/PMC27, superior corrosion resistance (at least at the edge), while retaining similar toughness and hardness. The use of the standard RWL34/PMC27 mix for the san-mai sides means that current Damasteel customers can use the steel with little change to their heat treatment and etching process. I do think the product would be more intriguing if they had used steels for the Damascus sides with higher corrosion resistance, particularly if every steel was produced with nitrogen alloying. Overall the new Damacore DC18N looks like a good steel for those looking for a stainless damascus san-mai product with a high performing core steel. 

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[1] http://damasteel.se/inspiration/damacore-dc18n-4/

[2] https://www.uddeholm.com/app/uploads/sites/36/2017/08/VANAX-Superclean-eng-1705-e1.pdf

[3] https://knifenews.com/damasteel-implements-nitrogen-steel-in-damacore-dc18n/

[4] http://damasteel.se/inspiration/kitchen-knives-middleton-made-knives-2/

[5] Ejnermark, Sebastian, Thomas Hillskog, Lars Ekman, Rikard Robertsson, Victoria Bergqvist, Jenny Karlsson, Petter Damm et al. “Corrosion and wear resistant cold work tool steel.” U.S. Patent Application 14/917,521, filed July 28, 2016.

[6] https://knifesteelnerds.com/wp-content/uploads/2018/10/Bohler-Uddeholm-toughness-testing-1.pdf

[7] Westin, Leif. “Martensitic chromium-nitrogen steel and its use.” U.S. Patent 7,700,037, issued April 20, 2010.

[8] https://knifesteelnerds.com/2018/05/21/154cm-development-properties-legacy/

[9] https://knifesteelnerds.com/2018/03/16/micrographs-of-niolox-cpm-154-and-aeb-l/

[10] https://www.crucible.com/PDFs%5CDataSheets2010%5CdsS35VNrev12010.pdf

[11] Almström, Linda, and Camilla Söderström. “Alternative materials for high-temperature and high-pressure valves.” (2010).

[12] http://damasteel.se/wp-content/uploads/2018/05/Data_Sheet_Martensitic_Damascus_Patterned_Steel.pdf

[13] http://damasteel.se/inspiration/damacore-dc18n-3/