Vacuum investment casting is an advanced variation of the conventional investment casting process. By creating vacuum in the mold cavity before pouring the molten metal, it eliminates or significantly reduces gas porosity and dissolved gases in the castings, thus improving mechanical properties and surface quality. The key benefits include higher strength, better surface finish, improved coatability, ability to cast challenging alloys, thinner sections possible. It does require more complex mold sealing and higher cost. Vacuum investment casting first builds a wax pattern, then a ceramic mold, burn out the wax, preheat and create vacuum before pouring metal in. It has wide applications from aerospace components to medical products.
Vacuum technology creates less porosity and cleaner castings
The key difference of vacuum investment casting is that it sucks air out of the mold cavity before pouring, creating a vacuum environment. This prevents gas pores from forming as the liquid metal solidifies. In addition, it reduces the dissolution of hydrogen, oxygen, nitrogen in the metal. So the castings have less microporosity and cleaner interior quality. The lack of gas pores also means higher density and improved mechanical properties.
Smoother surface and better tolerance capability
When molten metal meets air during pouring, oxidation reactions roughen the surface. Vacuum casting prevents this. In addition, without gas bubbles bursting out during solidification, it creates smoother as-cast surface quality. The reduced pressure inside the molds also lowers resistance to metal flow, allowing the castings to better fill fine details and achieve tighter tolerances.
Enables challenging materials and applications
By reducing dissolved gases and oxidization, vacuum process expands the castable alloys from steels, aluminum, brass to more challenging superalloys and reactive materials like titanium, zirconium etc. It also makes it possible to cast thinner sections without macroporosity defects. These benefits have made vacuum investment casting widely used in aircraft engines, aerospace, medical implants where high property requirements meet complex shape needs.
Vacuum investment casting brings key enhancements of mechanical properties, surface finish and shape complexity over conventional investment casting process. By creating a vacuum in mold cavity before pouring metal, it eliminates dissolved gas and reduces defects in the castings. The improved property and tolerance capabilities have enabled challenging applications from airplane and implants.