Investment casting of titanium alloys is a specialized process used to create parts with complex shapes and high precision. This method is particularly beneficial for producing castings with low surface roughness and precise dimensions. Investment casting, also known as the lost wax method, has been refined over centuries, adapting to modern requirements such as atmosphere control to accommodate the casting of reactive metals like titanium.
Titanium alloys are challenging to cast due to their high melting temperature and reactivity, which can lead to chemical reactions with most refractory materials at molten states. Key to the success of titanium alloy investment casting is the selection of shell materials that exhibit high chemical inertness to avoid reactions with molten titanium alloy. Carbon refractory materials, like artificial graphite, and oxide ceramic materials, including SiO₂, MgO, Al₂O₃, and ZrO₂, are commonly used. These materials are chosen for their ability to withstand the high temperatures of molten titanium alloy without softening, breaking, or chemically reacting.
The investment casting process involves creating a wax model of the desired part, which is then encased in a ceramic shell to form the mold. Once the wax is melted away, molten titanium is poured into the cavity left behind. This process can produce titanium castings with more than 90% metal utilization rate, offering significant cost savings compared to other manufacturing methods, particularly for complex shapes and high precision requirements.
One of the most widely used titanium alloys for investment casting is Ti-6Al-4V, favored for its excellent combination of strength, toughness, and corrosion resistance. This alloy finds applications across various high-performance sectors, including aerospace and medical implants. The alloy’s properties can be tailored through heat treatment, providing mechanical properties comparable to or even superior to wrought products.
Investment casting has emerged as a preferred route for manufacturing sophisticated titanium castings due to its ability to produce high-quality parts with complex shapes and fine details. This method has been successfully implemented as a cost-effective alternative to forged and wrought products, particularly in aerospace and military applications, where performance and cost-efficiency are critical.