Directional solidification and single crystal casting

Since the 1970s, directional solidificationtechnology has been used to cast super alloy turbine blades, bringing a newleap to the performance of gas turbines. Compared with common casting method,directional solidification blade has higher properties, especially hightemperature creep resistance and thermal fatigue resistance, under thecondition of identical alloy composition. This greatly extends the service lifeof the blade and increases the working temperature of the blade. The so-calleddirectional solidification is to obtain columnar crystal structure parallel tothe direction of blade principal stress by strictly controlling thesolidification process of casting. The leaves with bundles of columnar crystalsare directionally solidified leaves. On this basis, a further measure is takento allow only one columnar crystal to grow, and the resulting blade will haveonly one grain, that is, a single crystal blade. The single crystal bladeeliminates all transverse and longitudinal grain boundaries and its performanceis further improved.