Investment casting  Development of new blade alloys to achieve high temperature performance has required parallel development in alloy processing. Before the 1940s, gas turbine engine blades were  iron-based alloys through cold wrought. In the 1940s and 1950s, investment casting and vacuum melting were introduced to manufacture engine blades. In the 1970s, the directional solidification (DS) process was invented and made a great advance in the thermal capability of the blades. The grain boundaries were significantly decreased  and the  crystals were  all aligned in the direction of centrifugal stress. Based on the DS casting process, single crystal (SX)  blades were exploited, which are free from high angle grain boundaries and therefore dramatically increase the melting point of turbine blades]. To date, all the modern Trent family of engines incorporate single crystal materials.  Nowadays, turbine blades are designed with complex geometries and intricate channels which allow cooler air flow within  and  along  the  blades  during  operation .  Therefore,  turbine  components  are  usually  produced  by investment casting. 

 the investment casting process (also called lost-wax casting) involves the following steps: 

1. A pattern of the component of the casting is prepared by injecting molten wax into a metal mould. If necessary (such as for cooling passages in turbine blades), ceramic cores can be prefixed into the mould to intricate hollows for the castings. Wax patterns can be assembled in clusters to enable several blades to be produced in a single casting. 

2. The wax mould is then dipped  into ceramic slurry consisting of binding agents and mixtures of zircon (ZrSiO4), alumina (Al2O3) and silica (SiO2), followed by stuccoing with larger particles of the above materials. This process needs to be repeated several times until the shell thickness is thick enough to withstand the mechanical shock of receiving the molten metal.

 3. After the shell is constructed, the wax is removed in an autoclave or furnace. 

4. The ceramic mould is then fired to high temperature to build up its strength and make it ready to receive the molten superalloy. 

5. When the casting is finished, the investment shells are knocked off and the ceramic cores are leached out using a high-pressure autoclave by chemical means.