The individual turbine blades used in the exhaust region of jet engines must withstand high temperatures, high stresses, and highly corrosive operating conditions. These demanding conditions severely limit the material possibilities, and most jet engine turbine blades have been manufactured from one of the high-temperature super-alloys. The fabrication processes are limited to those that are compatible with both the material and the desired geometry. Through the 1960s and early 1970s the standard method of production was investment casting and the resultant product was a polycrystalline solid with thousands of polyhedral crystals. In the 1970s production shifted to unidirectional solidification, where elongated crystals ran the entire length of the blade. More recently, production now offers single crystal products. Investigate this product to determine how the various material and processing conditions produce products with differing performance characteristics.

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Rating chart for selecting materials Material Go-No-Go Relative rating number rating number xweighting factorl Material rating number screening Σ rel rating no. rating factors . weighting factor# 1 lowest to 5 most important Range- 1 poorest to 5 best "Code S satisfactory U- unsatisfactory FIGURE 9-A Rating chart for comparing materials for a specific application.