Investment casting titanium is one of the hardest jobs in the whole foundry world, and there’s a good reason for that. Titanium is a reactive metal, so once it melts, it can easily react with both the air and materials inside the mold.
This the reason why the process needs tighter control from the start of the process. The furnace atmosphere, ceramic shell, pouring conditions, and cooling stage must all be under strict consideration that it’s titanium being worked on.
So, we’ll be going through what titanium investment casting actually involves, the grades you’ll come across, and where these parts are actually used!
What Is Titanium Investment Casting?
Titanium investment casting is the lost-wax process applied to titanium and its alloys. The part is made in wax, and the wax is covered with ceramic. They’re then melted out to leave an empty space. Molten titanium is poured into that space and allowed to cool.
The basic idea is the same as other investment casting methods. The difference is that titanium reacts very easily when it’s hot, so the melting and pouring, along with the mold materials all need stricter and tighter control.
Why Titanium Needs Vacuum Melting
Titanium becomes highly reactive once it melts. Even small amounts of oxygen, nitrogen, or hydrogen can change the metal and make the finished casting more brittle. Therefore, vacuum melting needs to be done.
What Is Vacuum Melting?
Vacuum melting means melting materials inside a sealed chamber where there’s absolutely no air. Some systems also use an inert gas like argon to keep air away from the molten metal. This gives the foundry much better control over what the titanium comes into contact with.
Foundries often use vacuum arc skull melting, where the metal sits in a water-cooled copper crucible and never touches a hot container wall. Cooling helps keep the molten titanium from reacting with the container itself, which reduces contamination before pouring.
The shell has to change too because ordinary silica shells react with titanium and leave a hardened, contaminated surface layer called alpha case. The alpha case must be chemically milled off afterward. Yttria and zirconia face coats resist that reaction far better, though they cost considerably more.
Titanium Investment Casting Grades
There are a few titanium grades you’ll see more often in investment casting compared to others. The right one depends on the specific traits or the industry where you’ll be using them.
CP Titanium
Commercially pure titanium covers Grades 1 to 4. It’s not as strong as Grade 5, but it gives excellent corrosion resistance. That makes CP titanium a common choice for chemical processing equipment and other parts exposed to harsh liquids or chemicals.
Grade 23 ELI
Grade 23 ELI is a cleaner version of Ti-6Al-4V with tighter limits on elements such as oxygen and iron. It offers better ductility and fracture toughness, which is why it’s widely used for medical implants and other medical titanium castings.
Ti-6Al-4V (Grade 5)
Grade 5 is one of the most common titanium investment casting grades. It has about 6% aluminum and 4% vanadium. Its tensile strength is around 895 MPa, while its density is only about 4.43 g/cm³. It can also work at temperatures around 400°C.
That mix of low weight and high strength makes Grade 5 especially useful for aerospace and defense parts.
What Is Titanium Investment Casting Used For?
You’ll mostly see titanium investment casting when the specific industry needs high strength and strong corrosion resistance from its parts or components.
Medical and Dental
Titanium is well accepted by the human body and resists corrosion. That’s why dental and medical companies use them for implants and other medical components.
Defense
Thanks to its being lightweight, it’s been an obvious choice for military and defense. Defense parts often need to stay strong without adding unnecessary weight, and titanium is the answer for that. They work well for aircraft and missile systems.
Marine and Chemical Equipment
Titanium handles seawater and harsh chemicals very well. They’re often used for specific material like pumps, valves, and other parts exposed to corrosive conditions.
Aerospace
Aircraft parts need strength without extra weight. Titanium offers both, making it a strong choice for engine parts, brackets, and structural components.
Pros and Cons of Titanium Investment Casting
Every process has its good and bad takes, and yes, titanium isn’t an exception. In fact, you’ll even realize that titanium’s characteristics are sharper than most. So, let’s take a look at some of the advantages and disadvantages of investment casting titanium.
The Pros
- High strength without the extra weight: Titanium can offer strength close to some steels while weighing much less. This is especially useful in aircraft and other weight-sensitive parts.
- Excellent corrosion resistance: Seawater and many chemicals have little effect on titanium, so it works well in marine and chemical equipment.
- Good for medical use: Titanium is widely used for implants because the body generally accepts it well and the metal resists corrosion.
- Less machining on complex parts: Investment casting can create shapes close to the final design. That matters with titanium because machining it can be slow and expensive.
The Cons
- Higher cost: Titanium casting usually costs much more than comparable steel or aluminum parts.
- Fewer foundries can make it: Special vacuum equipment is needed, which limits the number of suppliers.
- Extra surface treatment may be required: A hardened layer called alpha case can form during casting and may need to be removed.
- Longer lead times: The extra equipment, mold materials, and finishing steps can make titanium castings take longer to produce.
Is Titanium the Right Metal for Your Casting
At YTD Foundry, our strength is helping buyers choose the right alloy for the job. Although titanium isn’t something we work with, we offer a big menu of investment casting materials and can often offer a more practical option depending on your application.
Send us your sketch and material requirements, and we’ll review the part and recommend a suitable casting alloy for production! Get a free estimate!
