CN103436739B - A kind of rhenium-containing High-strength hot-corrosion-resistnickel-base nickel-base monocrystal high-temperature alloy - Google Patents

Abstract

The invention provides a kind of rhenium-containing High-strength hot-corrosion-resistnickel-base nickel-base monocrystal high-temperature alloy, the moiety of this alloy is formed and the mass percentage of each composition is: Cr:8.0 ~ 12.0%, Co:8.0 ~ 12.0%, Mo:0.5 ~ 3.0%, W:3.0 ~ 6.0%, Ta:4.0 ~ 8.0%, Al:3.0 ~ 5.0%, Ti:3.0 ~ 5.0%, Re:1.0 ~ 3.0%, C:0 ~ 0.4%, all the other are Ni, 6.5≤Al+Ti≤9, Al/Ti≤1.This alloy not only has excellent hot corrosion resistance, also has higher mechanical behavior under high temperature, good structure stability.Both go for ground and naval gas turbine high-temperature component, go for again space flight, high-temperature unit of aircraft engine.

Description

A rhenium-containing high-strength hot-corrosion-resistant nickel-based single crystal superalloy

technical field

The invention belongs to the technical field of nickel-based single-crystal high-temperature alloys, and specifically relates to a high-strength nickel-based single-crystal high-temperature alloy mainly suitable for components that bear high stress under high-temperature thermal corrosion conditions.

Background technique

The development of scientific and technological fields such as carrier-based aircraft and ground gas turbines in the marine environment requires engine materials to have both good mechanical properties and excellent thermal corrosion resistance. With the increase of engine and gas turbine inlet temperature, not only the alloy is required to maintain excellent hot corrosion resistance, but also higher requirements are put forward for its mechanical properties. At present, the thermal corrosion-resistant nickel-based single crystal superalloys developed in my country mainly include DD8, DD10 and DD413, etc. These alloys have good thermal corrosion resistance, but their strength is far below the level of the second-generation single crystal superalloys at home and abroad. . Therefore, there are few types of high-strength hot-corrosion-resistant single crystal alloys in China.

In view of the above background, it is desired to obtain a high-strength second-generation anti-corrosion nickel-based single-crystal superalloy that has good thermal-corrosion resistance and mechanical properties equivalent to those of typical second-generation high-strength single-crystal alloys. Hot corrosion of single crystal superalloys.

Contents of the invention

The purpose of the present invention is to provide a rhenium-containing high-strength hot-corrosion-resistant nickel-based single-crystal superalloy, which has good thermal-corrosion resistance while obtaining comparable mechanical properties to typical second-generation high-strength single-crystal superalloys.

The invention provides a rhenium-containing high-strength thermal corrosion-resistant nickel-based single crystal superalloy, the composition of the alloy and the mass percentage of each component meet the following requirements:

Cr: 8.0～12.0%, Co: 8.0～12.0%, Mo: 0.5～3.0%, W: 3.0～6.0%, Ta: 4.0～8.0%, Al: 3.0～5.0%, Ti: 3.0～5.0%, Re : 1.0～3.0%, C: 0～0.4%, the rest is Ni, 6.5≤Al+Ti≤9, Al/Ti≤1.

The high-strength thermal corrosion-resistant nickel-based single crystal superalloy provided by the present invention, the composition of the alloy and the mass percentage of each component meet the following requirements:

Cr: 9.0～11.0%, Co: 9.0～11.0%, Mo: 1.0～2.0%, W: 3.5～5.5%, Ta: 5.0～7.0%, Al: 3.3～4.3%, Ti: 3.6～4.6%, Re : 1.5～2.5%, C: 0～0.2%, the rest is Ni, 6.9≤Al+Ti≤8.9, Al/Ti≤1.

In the high-strength and heat-resistant nickel-based single-crystal superalloy provided by the present invention, the composition and mass percentage of impurities in the nickel-based single-crystal superalloy meet the following requirements: O≤0.003, N≤0.002, S≤0.004, P≤0.018, Si≤0.2, Pb≤0.0005, Bi≤0.00005.

The chemical composition design of the alloy of the present invention (the alloy grade is called DD420) is mainly based on the following reasons:

Alloy composition is a key factor affecting hot corrosion. Adding alloy elements can promote the formation of a stable oxide film on the surface of the alloy and reduce the hot corrosion rate of the alloy. In superalloys, Cr is the most effective alloying element to improve the hot corrosion resistance of alloys, and a certain Cr content can form a hot corrosion resistant Cr2O3 protective film. However, when the Cr content in the alloy is too high, the precipitation of topological close-packed phase (TCP) will occur. Therefore, the Cr content in the hot corrosion resistant superalloy is 8.0-12.0%.

Co has an inhibitory effect on the TCP phase and expands the heat treatment window, but too high Co content will reduce the solid solution temperature, resulting in a decrease in the high temperature performance of the alloy. In order to ensure the high temperature performance of the alloy, the Co content is controlled at 8.0-12.0%.

Mo and W are the most important solid solution strengthening elements in superalloys, but they are all elements that promote the formation of TCP phase, which is very unfavorable to the structural stability of the alloy. Moreover, W and Mo are very easy to form volatile oxides in high-temperature oxidizing environment, and it is difficult to form a dense oxide film. In the environment with Na ₂ SO ₄ , it is easy to cause acidic melting reaction, resulting in severe hot corrosion, especially It is a high Mo alloy, and catastrophic corrosion often occurs. Therefore, the content of Mo and W is limited to less than 3.0% and 6.0% respectively.

Al, Ti, Ta are the most important precipitation strengthening γ' phase forming elements in superalloys. Ti is also beneficial to improve the hot corrosion resistance of the alloy. Al can obviously improve the oxidation resistance of the alloy, but the protection performance against liquid Na ₂ SO ₄ is extremely poor. Therefore, the Ti/Al ratio of the alloy is greater than 1, and 6.5≤Al +Ti≤9. In addition to effectively improving the thermal strength of the alloy, Ta can also increase the oxidation resistance, corrosion resistance and casting performance of the alloy. However, if Ta is too high and the eutectic content of the alloy is high, the heat treatment of the alloy becomes extremely difficult. These factors the present invention controls Ta content in 4.0～8.0%.

Re is an effective solid solution strengthening element in superalloys, which can reduce the element diffusion rate during high temperature creep and durability, and significantly improve the mechanical properties of alloys. At the same time, Re is beneficial to the hot corrosion resistance of the alloy. However, Re forms volatile oxides during the oxidation process, which damages the integrity of the oxide film and deteriorates the oxidation resistance. In addition, excessive Re will also promote the precipitation of TCP phase. Therefore, the content of Re is controlled at 1.0-3.0%.

The addition of an appropriate amount of C can improve the casting performance of the alloy and reduce the recrystallization tendency of the alloy. In particular, the addition of C to form small-sized granular carbides can strengthen the grain boundary, thereby increasing the tolerance of the small-angle grain boundary of the single crystal alloy, and then improving the alloy. yield rate. However, the addition of excessive C will reduce the performance of the alloy, so the C content should be controlled at 0-0.4%.

The nickel-based single crystal superalloy described in the present invention utilizes pure Ni, Co, Cr, W, Mo, Ta, Ti, Al, Re, C and other elements to melt in a vacuum induction furnace, and cast into a master alloy whose chemical composition meets the requirements , and then remelted by directional solidification equipment (high-speed solidification method or liquid metal cooling method), and directional solidified into a single crystal test rod by using a spiral crystal selector or seed crystal method. Heat treatment is required before use.

Aiming at the background of the existing technology, the present invention has developed a high-strength hot-corrosion-resistant nickel-based single-crystal superalloy containing rhenium. Its hot-corrosion resistance is equivalent to that of M38 alloy, and its mechanical properties have reached or even exceeded the typical second-generation high-strength single-crystal superalloy. Level.

Advantage of the present invention and beneficial effect are described as follows:

(1) Compared with other existing nickel-based single crystal superalloys, the alloy of the present invention has excellent hot corrosion resistance, and the hot corrosion ability at 900°C is equivalent to that of M38.

(2) The durability of the alloy of the present invention is equivalent to or even better than that of typical second-generation single crystal superalloys. The durability at 982°C/248MPa is >200h, and the durability at 1000°C/235MPa is >100h. It is a high-strength thermal corrosion-resistant single crystal superalloy.

(3) The alloy of the present invention is stable in long-term aging at 900°C.

Description of drawings

Fig. 1 is the Larson-Miller curve comparison diagram of the alloy of the present invention and the first generation single crystal superalloy PWA1483 and the second generation single crystal superalloy Reńe N5 in the prior art;

Fig. 2 is the test of alloy 900 DEG C hot corrosion performance of the present invention;

Fig. 3 is the microstructure of the alloy of the present invention after long-term aging at 900°C for 2000h.

detailed description

The following examples will further illustrate the present invention, but do not limit the present invention thereby.

Specific preparation method requirements: Vacuum induction furnace is used to melt, and the master alloy whose chemical composition meets the requirements is cast first, and then the single crystal test rod is prepared, which must be heat-treated before use.

Embodiment 1-3:

See Table 1 for the chemical composition of the nickel-based single crystal superalloy sample of the present invention. For convenience of comparison,

Table 1 also lists the chemical composition of the typical first-generation nickel-based single crystal superalloy PWA1483 and the typical second-generation single crystal superalloy Reńe N5.

Table 1 Alloy of the present invention (Example 1-8) and PWA1483, ReńeN5 chemical composition list (wt.%)

alloy Cr co W Mo Ta al Ti Re C Ni Example 1 9.2 9 4 2 5.7 3.4 4.2 2.1 0.04 Remain Example 2 10 9 3.9 1.9 5.3 3.3 4 2 0.02 Remain Example 3 10.2 9 4 1.5 5 3.2 4 1.9 0.03 Remain PWA1483 12.0 9 4 1.9 5 3.4 4 - 0.06 Remain Reńe N5 7 8 5.0 2 7 6.2 - 3 - Remain

Note: "Remainder" in the column of Ni content in the table means "balance".

Example 4:

The Larson-Miller curves of the alloy of Example 1 of the present invention and the typical first-generation nickel-based single crystal superalloy PWA1483 and the typical second-generation single crystal superalloy ReńeN5 are shown in FIG. 1 . The durability performance of the alloy of the present invention is equivalent to that of Reńe N5 and higher than that of PWA1483.

Example 5:

The comparison between the 900°C hot corrosion performance of the alloy of Example 2 of the present invention and the hot corrosion resistant alloy M38 is shown in Figure 2.

Embodiment 6:

After the alloy is completely heat-treated, a long-term aging test at 900°C is carried out, and no TCP phase precipitates after long-term aging for 2000h. The microstructure of the alloy in Example 2 of the present invention after long-term aging is shown in Fig. 3 .

Claims (3)

1. A rhenium-containing high-strength thermal corrosion-resistant nickel-based single crystal superalloy, characterized in that: the composition of the alloy and the mass percentage of each component meet the following requirements: Cr: 8.0-12.0%, Co: 8.0-12.0%, Mo: 0.5-2.0%, W: 3.0-6.0%, Ta: 4.0-5.7%, Al: 3.0-5.0%, Ti: 3.0-5.0%, Re : 1.0～3.0%, C: 0～0.4%, the rest is Ni, 6.5≤Al+Ti≤9, Al/Ti≤1. 2. The rhenium-containing high-strength thermal corrosion-resistant nickel-based single crystal superalloy according to claim 1 is characterized in that the composition of the alloy and the mass percentage of each component meet the following requirements: Cr: 9.0-11.0%, Co: 9.0-11.0%, Mo: 1.0-2.0%, W: 3.5-5.5%, Ta: 5.0-5.7%, Al: 3.3-4.3%, Ti: 3.6-4.6%, Re : 1.5-2.5%, C: 0-0.2%, the rest is Ni, 6.9≤Al+Ti≤8.9, Al/Ti≤1. 3. according to claim 1 or 2 described high-strength heat-resistant corrosion-resistant nickel-based single-crystal superalloys, it is characterized in that: in the described nickel-based single-crystal superalloys, the composition and mass percentage of impurities meet the following requirements: O ≤0.003, N≤0.002, S≤0.004, P≤0.018, Si≤0.2, Pb≤0.0005, Bi≤0.00005.