Watch Case Materials Explained: Titanium

Watch Case Materials Explained: Titanium

Watch Case Materials Explained: Titanium Feature Articles

Please welcome Mr. İlker Özcan who will collaborate with aBlogtoRead.com on a few articles discussing materials and processes used in watch cases and other components. Ozcan is a professional Materials Engineer and owns a small R&D company (www.ndsgn.com) - and he loves mechanical watches and loves the exotic materials used in those watches. The purpose of this article series is to enlighten watch lovers about many aspects of watch materials so that everyone can make more educated decisions about the watches they are buying. Now on to Mr. Ozcan:

In this first article I have chosen to start with Titanium. Titanium has recently become very popular in high-end watches, and it is not without reason. For me, titanium is the best overall engineering metal ever! Is it however the best material for a watch case? Let’s take a look...

We engineers measure many properties to evaluate materials. Probably more types of properties than you have heard of if you are not a materials engineer. The most widely known of these properties are: strength, hardness, toughness, lightness and durability.

There are many alloys of titanium - like all engineering metals. The most widely known one is Ti-6Al-4V also known as Grade 5. It is the alloy that we will mostly denote when we say titanium in this article. It is used in very demanding applications such as aircraft components, missiles etc. Grade 2 titanium for instance is considered Commercial Purity and has inferior properties, however still a very good material.

Titanium has been around for the last two centuries, mostly in labs. In the last century methods to extract titanium in industrial amounts were developed. Until recently it has been used exclusively as an aerospace material, and it is slowly penetrating many markets, including watch industry. It is prohibitively expensive for many applications, with a price around 50 times of plain carbon steels. Still its price is much lower than precious metals.

Watch Case Materials Explained: Titanium Feature Articles

Now strength and toughness is where Titanium excels. Durability is not a scientific term used, we can think of it as the life of a material under cyclic loads, like a turning shaft i.e. fatigue life. Titanium is also great in this aspect, but it is quite irrelevant in a watch case, as a case never fails under fatigue. However it can be important if it is used inside the movement or for a crown or pushers. Strength denotes how much load a material can bear before failing. Titanium has very high strength around 1000 MPa for Grade 5. Five times that of ordinary steels. Even pure titanium is quite strong with Grade 2 being around 350 MPa. However there are alloys of steel that have even more strength than titanium, such as the tool-grade steel that we mentioned above, or some special Aerospace steels (e.g. 300M) have around 2000 MPa strength. Toughness denotes how big an impact a material can absorb before breaking apart. Titanium is really great here, absorbs lots of energy around 20 joules on impact test. However once again there are steel alloys that are better up to 150-200J for Austenitic stainless steels (there are also steels with very poor toughness such as Martensitic steels). Toughness beyond a point is however not important for watch related applications. It is not likely that you will smash you watch to such a degree that its case will break. Well before that would happen the delicate movement would fail.

As you  can see steel is very good, but where titanium actually pulls ahead is in terms of lightness (weight). It is circa half the weight of steel for the same volume with a density of 4.5 g/cc vs 7.8 for steels. So for a case that has the same strength, titanium case would be half the weight of a high strength steel case. And actually very high strength steels are almost never used in watches (they are used for aircraft components and tools for industry). Stainless steel is widely used, and it has lower strength (unless it is forged, which is again almost never used in watch industry). So a titanium case would be less than half the weight for the same strength.

Watch Case Materials Explained: Titanium Feature Articles

Another area where titanium is excellent at is corrosion resistance (e.g. its resistance to rusting). It is so good that it is almost impossible to rust titanium. It is impervious to all acids but nitric acid. And nitric acid is something you do not come nearby in your daily life. It’s corrosion resistance is similar to that of platinum, and in terms of engineering metals only zirconium can beat titanium for corrosion resistance. This corrosion resistance is the key to the hypoallergenic properties of titanium. It is so inert due to the oxide layer that forms on its surface, that it does not react with human body - thus being the material of choice for many medical applications.

There are some areas that titanium is beaten by steels. For instance the stiffness, which denotes how much the material deflects under loads. Steel has higher stiffness, much higher. But I think in a watch case it is not an important property. Maybe, except for diving watches.

The hardness of titanium is lower than some steels, so it scratches easier than most steel. However, titanium is much much harder than gold, platinum and aluminum. Coatings can improve the hardness of titanium as well, and there are many coatings out there that we might cover in another article. Grade 5 titanium has around 35 Rockwell C (Rc) hardness. Steels have a range of hardness from low values all the way up to 55 Rc for hardened carbon steels to 65 Rc for tool steels and even higher for special steels used for knifes (e.g. D-2 tool steel, S30V knife steel). Gold, platinum and aluminum are so soft that they are usually not even shown on the same Hardness scale (there are many hardness scales).

Watch Case Materials Explained: Titanium Feature Articles

Machining titanium is tricky. Welding, forging, casting and heat treating it are tough. So this trickiness adds to the high price of the titanium. Many properties that makes titanium such a good metal also make it hard to manufacture. With certain techniques that were developed in aerospace industry these hardships can be overcome. This is how we have nice titanium cases at affordable prices these days. However casting and welding processes are still very tricky, and we are unlikely to see a cast titanium case, or welded one at very affordable prices.

Titanium is such a good material that its usage is still increasing in fighter aircraft. For instance the F-22 utilizes more titanium than any western aircraft ever did. Its biggest competitor as a material is Carbon Fiber Reinforced Polymers (CFRP) and we will cover that in another article.

This article was written to generally inform people about titanium as a watch case material and has been obviously simplified. A larger discussion of titanium would expand on each of these topics and include many more. Though as watch lovers you hopefully have a new perspective on the popular metal. In conclusion, if you buy a titanium watch, especially one with a good coating, you will be happy with your decision.

  • Greg S

    Fantastic. Very interesting and I look forward to the rest of the articles in the series.

  • Ulysses31

    This is just the kind of thing I find interesting; the engineering side.  A good article and I hope we’ll see many more.

  • Eric S

    Thank you Ariel and Mr. Özcan for this highly informative post. I always wondered about titanium as a material for watches and knew a little, but this has really made me think twice about getting a watch in the metal one day. Like Greg and Ulysses said, I can’t wait for more posts like this one! Keep up the great work!

    • Glad it was interesting. Thanks.

  • VasilisAnagnostopulos

    how can one tell what grade their TI watch is?

    • ilker_ozcan

       @VasilisAnagnostopulos 

    • ilker_ozcan

       @VasilisAnagnostopulos If it is not stated on the watch you may contact the watch company and ask them. Otherwise there is no easy way for a user to determine its type without access to advanced tools.

  • momsfocus

    @DanGordon only 91 RT’s togo or 34 more followers whichever comes first https://t.co/YTLZAbm4

  • Great post and coverage of my favorite material for watches prior to moving into composites which I am happy to see Mr.  Özcan will be covering.  

  • arthurdavis

    Excellent.  Keep it up

  • nateb123

    Personally I would say lightness of a watch is a fault.  A cheaply made Chinese quartz watch is lighter than a well-engineered automatic too so why is lightness so great, especially when we deliberately choose bigger, heavier watches?  I don’t want my watch to disappear from my perception, I want to feel it is there.
     
    Plus I prefer the silvery colour of stainless steel (which is harder to scratch anyways) versus the grayish tone of Titanium.  To each his own, but for a silver/gray tone watch, I would always choose stainless.

    • ilker_ozcan

       @nateb123 It is true that many customers percieve lightness as a sign of cheapness, and most watch manufacturers do not try to make very light watches except for maybe a few special models in their collection. What a watch company can do is make a light case and use the saved weight for a better movement. A bigger rotor or another barrel can be useful. Maybe as important as being heavy is a solid feeling, which arises from stifness, and titanium shall be more than sufficient at this aspect. Also with the recent trend of extra large watches, I think weight on its own is being an issue. If one is not used to big watches, it can take days to get used to them.
      In the end, its all personal preferences. CFRP and ceramics are even lighter, so is aluminium and there is a market for them too.

  • TJH

    Hi , I have phased into all titanium and super titanium watches over the last 10 years , once you have one you won t  go back to stainless steel. With the larger say Citizen chronograph types as one example they are large and even in titanium are up there in weight but are a good balance in feeling quality etc , would be too heavy if in stainless steel. The titanium warthes and bands do not scratch very much contrary to reports I thought even less that stainless steel , I have been baffled by that advice on forums. Super titanium doesnt seem to scratch at all it is so hard. Super titanium watches are much lighter for sure but the feel and smooth surface appeal is great and makes up for quality feel if you miss the heavy feel. cheers Terry

    • Thanks for the comment Terry.

      • Tom

        I read this article in the hopes it would answer my question relating to Titanium nitride black coating on a titanium TAG, and if the coating would be more susceptible to scratching if it was bonded to a stainless steel watch versus a titanium one. Can anyone shed light? Thank you.

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  • TroyGorrell

    I can live with the simplification to the point of almost being erroneous, but there is one glaring error.
    Titanium is totally immune to oxidizing acids like nitric, as they only increase the resistant oxide layer. Titanium is practically worthless in the presence of reducing acids like hydrofluoric, as they consume the oxide layer making the material very susceptible to corrosive attack. In any case, I agree that it is unlikely a watch will be exposed to these substances, and if it is, you have MUCH bigger problems to worry about. (Hydrofluoric acid will be absorbed by the skin, and attack the calcium in your bones, liquefying the victim from the inside out – very bad stuff!)
    Also missed is the biocompatibility of titanium – no titanium implant has ever been rejected or caused reaction, where stainless steel is frequently.

  • adrock73

    I am not concerned with weight of my watch, but rather the durability of the metal. I tend to scrape, scratch & knock into things with my watches. Which metal is better for a clumsy watch-wearer like myself? Is titanium really worth the 20% cost increase compared to stainless?
    Thanks,
    Adam T.

  • LuisAmaroLopez

    how can   polish a titanium watch?

  • Thanks for detailed insight about Ti-6Al-4V aka Grade 5. Explains in depth titanium as a watch case material.

  • Whitehall

    I think the author implies that titanium watch cases and bracelets are made by machining. Did anyone get the same impression?

  • Matthew Blair

    A great read. Well put together.

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