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by nosse
5233 days ago
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For most materials monocrystalline casting is still science fiction. And as much as I've studied the subject, metals are used so much because they have good strength properties at relatively high temperatures. These glass metals turn liquid at relatively low temperature. So I have to say that it's not simple as you say. I'd anyhow be more worried about oriented strength of forged parts. And internal stresses. And funny material folding that sometimes happens in badly designed die forging. |
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On the topic of forged turbine blades, the oriented strength of the resultant blade _is_ the advantage of using forging over conventional casting for a polycrystalline blade. Since the load on a turbine blade is mostly axial it makes no sense to not have favorable grain orientation to maximize strength in the axial direction. As a result, turbine blades are forged such that the grain orientation and size is elongated and coarse. This minimizes grain boundary area perpendicular to the load direction and thus minimizes creep at the high operating temperatures of a gas turbine.