single crystal blade

Single crystal blade English name: single crystal blade, after 3 generations of development. The first generation is: Nickel-based superalloy The second generation is: Oriented grain boundary polycrystalline

Definition: A cast blade with only one grain. The directional crystallization blade eliminates the lateral grain boundaries sensitive to voids and cracks, and makes all grain boundaries parallel to the stress axis direction, thereby improving the performance of the alloy. The single crystal blade eliminates all the grain boundaries, without the need to add grain boundary strengthening elements, so that the initial melting temperature of the alloy is relatively increased, thereby improving the high temperature strength of the alloy and further improving the overall performance of the alloy. The whole casting of the single crystal blade is composed of a single grain of cast superalloy. This is a way to further improve alloy strength and service temperature after directional solidification casting of superalloys. The ideal structure of single crystal blade castings is leaf root, leaf body and leaf crown, which are composed of multi-phase single crystals without defects. The crystal orientation should be in the <001> direction, and the deviation from 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 process as directional solidification. The difference from directional solidification castings is only that a crystal selector or seed crystals are added on the upper part of the water-cooled chassis to control the single crystal into the casting. In the early stage of the brief history, the single-crystal casting superalloys used ordinary casting superalloys. In this case, the single-crystal casting superalloys did not significantly improve other properties except the improvement of lateral strength and plasticity compared with the directional solidification casting superalloys. In the late 1970s, single-crystal cast superalloys with grain boundary strengthening (see superalloy grain boundary strengthening) elements appeared, such as PwAl480 and NASAIR100 in the United States. After removing the grain boundary strengthening elements such as carbon, boron, zirconium, hafnium, etc., the initial melting temperature of the alloy is increased, which allows the solution treatment temperature to be increased to obtain a finer and dispersed Y ‘phase (see intermetallic compound phase of high-temperature alloy material ) To make the potential of the alloy more fully realized. After more than 20 years of development, more than 20 single crystal casting superalloys have appeared. These alloys can be divided into three generations: the first generation is represented by PwAl480, and its temperature resistance has an advantage of 25 ° C over the best directional solidification casting superalloy PwAl422; the second generation is represented by PwAl484, which is improved over the first 25 ℃; the third-generation single crystal alloy is being developed.

Edited By: Kevin Liu; Copyright: SIMUWU Vacuum Furnace

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