These crystals are the gems of turbine efficiency

Single-crystal turbine blades, with a much greater resistance to high-temperature creep and fatigue, are used in many applications requiring high performance and strength. Although they are costly, the single-crystal turbine blades are essential for modern gas turbines. Most gas turbines are axial flow machines, converting the heat from combusted fuel into thrust power. The thermal efficiency in gas turbines increases with greater air flow temperatures which can be greater than the melting point of conventional turbines.  Conventionally cast turbine airfoils are polycrystalline, consisting of a three-dimensional mosaic of small metallic crystals, or "grains," formed during solidification in the casting mold. Weaknesses occur at the boundary of each grain. These grain boundary weaknesses can lead to creep, shorten cyclic strain life, and decrease overall ductility which will ultimately shorten the turbine blade life. Creating single-crystal turbines begins with cast liquefied metal that is cooled under very controlled mold temperatures. Ideally, the single-crystal turbine blade will have no grain boundaries and hence eliminate many of the inherent weaknesses that plague conventional turbine blades. Single-crystal turbines have recently been introduced to new, large land-based gas turbines, where they hold promise of minimum life cycle cost for increased turbine temperatures.  Read the full article in Machine Engineering Magazine.

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