Some examples of materials suitable for investment casting:
1. Carbon Steel
Carbon steel can be taken as a proxy for various alloys with detailed property differences that are very widely used in all sectors. These materials are extensively used in investment casting, as the method enables net shape creation of parts requiring limited post-casting work. It is best suited to complex and intricate parts, of high dimensional accuracy/repeatability, high value, and high-quality requirements.
The use of carbon steel for investment casting requires careful alloy selection. Advice from casting experts is crucial to ensure the final casting meets the requirements. In particular for steels, investment casting offers benefits that lighter and lower-melting-temperature metals can also derive from die casting, which is impractical in all steels.
2. Aluminum
Aluminum refers to a broad category of alloys based on aluminum with minor components added to alter properties in a variety of ways such as: toughness, machinability, and hardenability. It is a commonly used material for investment casting due to a desirable range of properties and characteristics. Aluminum offers many benefits in general manufacturing and is well suited to investment casting. It has great casting characteristics such as: low melting point, moderate viscosity, and generally low shrinkage during solidification. Most aluminum alloys suited to investment casting, however, are relatively high-cost. Aluminum is well suited to high-value and moderate- to high-volume investment cast components in which the fine detail is limited and the quality level of equipment is higher than the norm.
3. Stainless Steel Alloys
Investment casting of stainless steel can sometimes result in a poor surface finish because of influences from the casting process, and material properties. The chromium and nickel content of stainless steel forms a robust oxide layer that can lead to surface irregularities and a rough finish due to chemical interaction with the refractory materials. Certain coatings and good refractory material selection can prevent much of this. Various stainless steel alloys have different casting characteristics and reactivity with mold materials. For that reason, careful selection by experienced operators is often necessary. Tight control of all aspects of the process, from wax pattern quality to post-cast surface finishing, is required, to avoid the challenges in achieving good results in stainless steel investment casting.
4. Brass
Brass is extensively used for both functional and decorative investment castings, due to its versatility, cosmetics, and corrosion resistance. As a casting material, brass benefits from low melt temperature and viscosity and low shrinkage as it cools to solid. Brass has a bright golden appearance and is often used for decorative and ornamental applications. Brass properties in the casting process also offer some challenges. For example, zinc evaporation from the melt can lead to changes in properties. Brass alloys are also prone to oxidation in the liquid state, influencing surface quality. Good mold design, atmospheric oxygen control, and mold coatings can moderate this effect.
5. Glass
The investment casting of glass is an unusual technique that is used to a limited degree in art and decorative object manufacture. It differs from the metal process in that the flask is generally charged with powdered glass, with a large hopper (also filled with glass powder) over the sprue. The whole is then placed in a kiln and the glass is melted and unified in the mold, with the hopper feed. This ensures that the air space (between powder particles) is pushed full as the glass melts. In all other regards, the process is much like investment casting metal except that the part requires considerably more care in demolding and handling.
