Directional Solidification

Directional solidification is a casting technique in which a molten metal casting is cooled and solidified progressively from one end toward the other, so that the solid-liquid boundary sweeps steadily across the casting in a single direction rather than solidifying inward from every mold wall at once the way an ordinary casting does. Because the metal's grains grow lengthwise in the direction the solid front travels rather than forming in many random orientations, a directionally solidified casting has far fewer weak grain boundaries running across its length, giving it much greater resistance to creep and thermal fatigue under sustained heat and stress. The technique is widely used in the aerospace and power-generation industries to cast turbine blades for jet engines and industrial gas turbines, where its improved creep resistance and thermal-fatigue life directly extend a blade's working life under continuous high-temperature operation.