Single crystal casting high temperature alloys

The ideal organization of a single crystal blade casting is a leaf root, a leaf body and a leaf crown, all consisting of multiphase single crystals without defects. The crystal orientation should be 〈100〉 direction, and the deviation between the direction of the main stress axis of the blade should not be greater than 10 degrees. Single-crystal castings can be prepared with the same equipment and processes as directional solidification, and directional solidification castings differ only in the upper part of the water-cooled chassis to join the crystal selector or child crystal, in order to control the single crystal into the casting. Single crystal casting high temperature alloy (single crystal superalloy) refers to the entire casting by a grain of casting high temperature alloy. This is a way to further improve the strength and service temperature of the alloy after the directional solidification casting high temperature alloy. Single crystal casting high temperature alloy as a new type of aero-engine blade material is widely used.

Features
(1) minimize the content of grain boundary strengthening elements, the alloy does not contain carbide, boride, just simple γ-γ' two-phase system, making the initial melting temperature as high as possible; (2) with the help of high-temperature homogenization treatment, so that the incipient γ', γ-γ' eutectic disappears, after appropriate aging treatment to adjust the combined γ ' phase particle size.
(3) adjusting in a wide composition range in the γ-γ' two-phase system alloy to obtain as many γ' phases as possible to 65%-75% by volume, and obtaining solid solution strengthening of both γ and γ' phases.
(4) Maintain sufficient thermal corrosion resistance and good processability of the alloy.
In addition, single crystal cast high temperature alloys are anisotropic, with the <100> direction being the preferred direction for crystalline growth of the alloy with higher creep strength and lower elastic modulus. The highest creep strength orientation is the <111> direction. The highest fatigue performance is in the <001> direction.