316L vs submarine steel?

[TrickTock]

This is truly fascinating information, but I've got to ask...did you stay at a Holiday Inn Express last night?

Now that the properties of the alloys has been explained, how do the hardening processes differ between manufactures. I understand Tegimenting is nothing more than a Sinn trade name for Klosterizing. Marketing aside, how does that really differ from Damasko's “ice-hardened, nickel-free stainless steel”? We all know what Damasko says, but is it true or mostly marketing hype?

I wish I had known about the "holiday inn express" learning method. Instead I wasted my time getting a PhD. I work in the petrochemical industry and have spent many years specifying alloys and fabrication methods for process equipment. And my family owns a large metal fabricating business that serves automotive and aerospace industries. So I get my dose of metallurgy talk at family gatherings too.

I think the discussion comparing Sinn's tegimenting (very hard shell on a soft core) to Damasko's ice-hardening (medium hardness all the way through) has been well covered on the watch forums. Some damage scenarios will mess up a Sinn, but not a Damasko -- and vice versa. It just depends on the nature of the unfortunate watch accident. Both are great watch cases that can look new for many years if there are no severe accidents.

Damasko was smart to patent their choice of steel alloy for all watch case applications. They use Cronidur 30 (X30CrMoN15 1). They did not invent this steel, nor did they develop its ice hardening process. But they were brilliant in finding novelty in order to secure a patent. Here is their explanation of novelty from their US patent:

"these materials have heretofore been regarded by experts as unsuitable for the manufacture of wrist watches, due to the fact that such steels are highly magnetizable, especially by external magnetic fields, so that they function as permanent magnets whose magnetic field strongly impairs the highly sensitive clockwork of a wrist watch. The invention is based on the realization that the aforementioned hardenable steel surprisingly is suitable for wrist watch cases, and especially if in the interior of the case a ring or plate enclosing the clockwork is made of a diamagnetic metal."

So Damasko is saying that nobody thought to use this type of steel because it can become magnetic and screw up the movement. They solve this problem by putting in a diamagnetic inner cage around the movement. This might seem obvious to a WIS in hindsight, but probably was quite impressive to the patent examiner.

The Damasko ice-hardening is a complex process. I haven't yet seen it described anywhere on the web, so here it is: First the metal is heated to above 1000°C, then rapidly quenched to room temperature in oil. This is followed by deep freezing at – 80 °C for 1 hr, then tempering for several hours at 160°C to give hardness >710 HV. The Pitting Resistance Equivalant is 30 points which is similar to 316L. The nickel-free composition is great for people with allergies.

So what about Bremont watches? Here is a quote from QP magazine: http://www.jurawatches.co.uk/PDF/bre...ingyarnQP1.pdf

"Furthermore, all the cases and buckles are brought back to England to be treated for hardness with B-EBE2000 technology, a process used on the turbine blades of jet engines. The cases are heated to high temperatures and carbon diffusion is used to increase the overall underlying hardness of the case to 1,200 Hv on the Vickers scale (normal watch-grade stainless steel is more like 280 Hv in hardness). Argon electron ions then prepare the surface of the case followed by a metallic ceramic coating at temperature, bringing the case hardness up to 2,000 Hv – the same hardness as sapphire crystal.

Based on this info, Bremont is kolsterizing, then plasma spray coating. Since this is done in England, they are probably using Poeton Apticote 800/24. This is a tungsten carbide and cobalt coating applied with an argon plasma torch. That gives hardness of 2000HV, and is used on jet turbine blades. Poeton does work for Airbus and Rolls Royce.

DLC (Diamond Like Carbon) coating is starting to get used by lots of watch companies in the last couple years, like Glycine, Ball, Bremont, Linde Werdelin, MKII, Perrelet, Richard Mille, Panerai, Montblanc, Citizen, and Casio. The quality of DLC coating is highly dependent on the coating vendor. If done right, these will be >2000HV and will take a beating. I have found these coatings to be highly variable in ultimate hardness. And some have even delaminated around part edges.

If I had my own watch company I would use Nirosta 4565 for the case. It has a Pitting Resistance Equivalent >50 for ultimate corrosion resistance in seawater. I would harden it with the Swagelok SAT12 process (low temperature colossal supersaturation) to get above 1500 HV.

Don't get me started on ceramic cases...

[andy_s]

Very interesting - thanks for posting, fascinating stuff.

[CMSgt Bo]

I appreciate you giving us a "peek under the tent" of horological metallurgy and breaking it down into layman's terms so even a knuckle dragging mechanic like myself can understand.

With your background and assuming you're a WIS too, what do you look for in a watch?

[Mark McK]

Tricktock, Thanks for the informative posts. Very interesting stuff.

[TrickTock]

I appreciate you giving us a "peek under the tent" of horological metallurgy and breaking it down into layman's terms so even a knuckle dragging mechanic like myself can understand.

With your background and assuming you're a WIS too, what do you look for in a watch?

Here is what I'd look for in a watch as far as new technology developments that I'd like to see:

Completely oil-free mechanical movements (many are working toward this and Diapal is a significant step). This is tough considering a typical movement beats just over one billion times in four years. It would be nice to extend service times to >10 year intervals.

Use of steel that won't corrode from sunblock.

Harder and more durable AR coatings for sapphire crystals.

Better microadjust mechanisms on steel bracelets that can be changed on-the-fly as wrist size varies throughout the day.

Better adhesive systems for luminous inserts so they don't jump off the bezel.

Better inks for printing on the bezel's number indentations , that won't delaminate over time.

A quartz watch movement with higher beats per hour -- you could have a smoother second hand travel at the expense of battery life. But with large cases in style, and more room to accommodate battery volume, I'm convinced a 44mm watch could run 2+ years at 28800 bph on lithium.

Better sealing mechanisms on the crown to avoid the use of delicate threads that wear over time.

[holdemchamp1225]

Here is what I'd look for in a watch as far as new technology developments that I'd like to see:

Completely oil-free mechanical movements (many are working toward this and Diapal is a significant step). This is tough considering a typical movement beats just over one billion times in four years. It would be nice to extend service times to >10 year intervals.


I completely agree with this assessment and there are several companies working towards this already and if I am not mistaken, JLC (which is my favorite manufacturer) already has a couple of their movements (Extreme Lab) which require NO lubrication!!



Harder and more durable AR coatings for sapphire crystals.


Yes, please!!



Better microadjust mechanisms on steel bracelets that can be changed on-the-fly as wrist size varies throughout the day.


Absolutely a MUST HAVE. Glashutte Original, Omega, and Rolex have recently come out with some brilliant micro-adjustment buckles that work amazingly! I currently have a U1000S and wish that it had a micro-adjustable buckle such as the one on the GO Sports Evo or Omega Ploprof as it would be infinitely more comfortable throughout the day. As with others, my wrist swells and shrinks throughout the day and with the standard buckle, it is difficult to get a great fit and unnecessarily more hassle to adjust as it requires a tool!



Better inks for printing on the bezel's number indentations , that won't delaminate over time.


Completely agree.



A quartz watch movement with higher beats per hour -- you could have a smoother second hand travel at the expense of battery life. But with large cases in style, and more room to accommodate battery volume, I'm convinced a 44mm watch could run 2+ years at 28800 bph on lithium.


Seiko's Spring Drive, although a hybrid movement of quartz and mechanical, has the ABSOLUTE smoothest sweep seconds hand on the market and the technology is FAR superior than anything else I can think of in terms of a quartz regulator with mechanical parts and implementation.



Better sealing mechanisms on the crown to avoid the use of delicate threads that wear over time.

All great ideas and hopefully Sinn and other companies take some hints!!

[rationaltime]

Hello TrickTock,

You mentioned:
"If I had my own watch company I would use Nirosta 4565 for the case. It has a Pitting
Resistance Equivalent >50 for ultimate corrosion resistance in seawater. I would
harden it with the Swagelok SAT12 process (low temperature colossal supersaturation)
to get above 1500 HV."

I suppose having a high nickel content improves the corrosion resistance. Did you consider the
possibility of nickel allegeries (if you believe in that)? While I don't consider stainless 316L to be
low nickel, perhaps the finished product does not have nickel homogeneously distributed on the
surface. Do you care to comment on that?

Thanks,
rationaltime

[Janne]

My son has a Nickel allergy, a bad one. He is OK with the watches he wears, Omega, Tissot, and some japanese ones.

Does Sunblock increase the chance of corrosion?

The Sinn US has a batterylife of many years. 7?

[TrickTock]

Some people are genetically predisposed to develop nickel allergies. It is a contact sensitizer, and the prevalence of allergy is 10-15% of women and 1-2% of men (according to the Nickel Institute, June 2009). Those figures correlate with body piercing -- more exposure means that people are more likely to sensitize if they are predisposed. However most of these people with nickel allergies are fine with exposure to 316L, which contains nickel within the alloy, but not free nickel.

The nickel-containing alloys can release small amounts of nickel upon corrosion and wear. Alloy 316L, most commonly used in watches, will release less than 0.2 micrograms per week, per square centimeter of skin contact. But a very small portion of people are super-sensitive and are even allergic to 316L.

Why is nickel in most stainless steels? The main purpose of adding nickel is to stabilize the austenite structure of iron, which makes the steel non-magnetic and less brittle at low temperatures. Chromium, molybdenum, and nitrogen serve the purpose of increasing corrosion resistance.

The Damasko steel, Cronidur 30, is martensitic and has no nickel, so won’t bother anyone with nickel allergies.

Nirosta 4565 contains 16-19% nickel, so it could be allergenic to some people with severe nickel allergies.

Yes, sunscreen can speed up discoloration and corrosion of 316L. It has a lot of organic chemicals which vary depending on the brand/formulation. It is common to do environmental testing of plastics, metals, and fabrics for sunblock exposure, and even synthetic human perspiration!

[TrickTock]

Good info Bruce. I hope JLC continues to innovate and get these oil-free movements into the more accessible price range of their "lower end" stuff (below six figures)! They are definitely at the leading edge.