Structure and Its Influence on Ni – Base Superalloy Mechanical Properties

The structure of polycrystalline Ni – base superalloys, depending on a heat – treatment, consist of solid solution of elements in Ni (γ - phase, also called matrix), primary carbides MC type, intermetallic precipitate Ni3(Al, Ti) (γ΄- phase), and secondary carbides M23C6 type. Shape and size of these structural components have a significant influence on final mechanical properties of alloy. For instance the precipitate γ΄ size greater than 0.8 mm significantly decreasing the creep rupture life of superalloys and also carbides size greater than 50 mm is not desirable because of fatigue cracks initiation.
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