investment casting
Investment casting is the jeweller's ancient lost-wax trick scaled up to engineering. You make an exact copy of your part in wax, dip it repeatedly in a fine ceramic slurry until a hard shell builds up around it, then heat the whole thing so the wax melts and runs out, leaving a ceramic mold that is a perfect negative of the part. Pour metal into that shell, let it freeze, break the ceramic away, and you get a casting with crisp detail and a smooth surface almost ready to use.
The word investment means the ceramic that clothes, or invests, the wax pattern. The steps are: injection-mold the wax pattern, assemble several onto a wax tree, dip-and-stucco to build the ceramic shell, fire the shell to harden it and burn out the last wax, pour the metal, then shell-off. Because the mold is a single seamless piece and can capture fine geometry, investment casting makes shapes too intricate to machine, in metals too tough to shape otherwise, from surgical implants to jet-engine turbine blades.
This is the premium end of casting: excellent surface, near-net-shape (little machining), and it handles high-melting superalloys. Its power shows in turbine blades, where the ceramic mold can even be designed so the blade solidifies as a single crystal with no grain boundaries, which resist creep at high temperature. The honest trade-off is cost and speed: each wax pattern and shell is consumed, so parts are expensive and slow, justified only where the shape and performance demand it.
A nickel-superalloy turbine blade is investment cast in a ceramic shell shaped so that solidification proceeds from one end, growing a single crystal with no grain boundaries to weaken it under creep at over 1000 degrees C.
Investment casting can control not just shape but grain structure itself, which is why the toughest turbine blades are cast this way.
Investment casting gives fine detail and near-net shape but is slow and costly because each wax pattern and ceramic shell is used once; it is chosen for value, not volume.