A New Process for Microstructure and Performance Optimization of Low Rhenium Single Crystal Castings

Abstract

The invention belongs to the field of nickel-base high temperature alloy, and particularly relates to a novel process for optimizing the microstructure and performance of a low-rhenium single-crystal casting. The novel process is characterized in that an experimental means of combining a computer simulation software with differential thermal analysis is adopted, so that a heat treatment process system is determined more accurately; meanwhile, the hot isostatic pressing technology and the heat treatment technology are combined, the defects such as microporosity and shrinkage in the single-crystal casting are effectively eliminated, the surface recrystallization problem of the casting in the conventional method is avoided through complementary advantages, and both the strength and the endurance property of the single-crystal casting are improved; moreover, as a stepped temperature rising method is adopted, the phenomenon that the conventional heat treatment process can easily cause incipient melting in the casting is avoided; and besides, three times of aging treatment is adopted, the novel process has the advantage that more gamma' strengthening phases are precipitated compared with the conventional aging treatment, the strengthening phases are uniform in distribution, appropriate in sizes, and regular in shapes, and the anti-fatigue and anti-deformation performances of the alloy are further improved.

Description

technical field [0001] The invention belongs to the field of nickel-based high-temperature alloys, and relates to a new process for optimizing the structure and performance of low-rhenium nickel-based single crystal alloys. Background technique [0002] Nickel-based single crystal superalloys have good creep and fatigue resistance, good oxidation resistance and corrosion resistance, and are widely used in hot end parts of aero engines and industrial gas turbines. With the development of aerospace technology and gas turbine technology, the working temperature of superalloys has also increased accordingly. Therefore, the content of refractory elements in alloys has continued to increase. In the third generation of nickel-based superalloys, Re, Mo, W, Ta and other strengthening The total content of elements has exceeded 20wt%, and the element Re plays an important role, so the Re content of 0%, 3%, and 6% is used as the standard for distinguishing the first, second, and third g...

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Problems solved by technology

[0003] The optimized process design and research on nickel-based single-crystal superalloys have been relatively common. Through patent retrieval, it is found that: Chinese Patent Document No. CN104404418A "A Heat Treatment Method for Nickel-based Superalloys" records a heat treatment method. Although this method It can improve the hot workability of the alloy, but without homogenization heat treatment, the initial structure of the alloy is not uniform, and the initial melting temperature is low; Volume fraction, which reduces the mechanical properties of the alloy at high temperatures

[0004] Chinese Patent Document No. CN104746145A records "Heat Treatment Process of Nickel-based Single Crystal Superalloy". This method can improve the high-temperature durability of superalloys. However, the initial melting temperature of the third-generation superalloys reaches above 1350°C. The temperature parameters set in the literature At the same time, due to the slow diffusion rate of refractory elements, the solid solution time of this method is too short, the improvement effect of element segregation is not obvious, and the stepwise heating is not adopted, it is easy to cause interdendritic Incipient melting in low melting point region

[0005] Foreign patent document number RU2380454 "Hot isostatic pressing treatment method for single crystal nickel-based superalloy castings" records a hot isostatic pressing treatment technology for single crystal superalloys. Although this method can also achieve the purpose of improving the performance of castings, However, there is no combination of homogenization heat treatment, solution treatment, and aging treatment, resulting in obvious segregation and eutectic defects in the alloy.

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