TWI657147B - A HIGH STRENGH Ni-BASE ALLOY - Google Patents

Abstract

The present invention is directed to a high stress nickel-based alloy characterized in that the chemical composition comprises, by weight: Ni is 50.0 to 56.0 wt%, Cr is 18.0 to 20.0 wt%, and Nb is 4.0 to 5.5 wt%, Mo. It is 2.8 to 3.3 wt%, Al is 1.3 to 1.6 wt%, Ti is 0.6 to 0.8 wt%, and the rest is composed of Fe and unavoidable impurities.

Description

High stress nickel base alloy

This invention relates to an alloy, and more particularly to a high stress nickel based superalloy.

Nickel-based alloys are the most widely used alloys in high-temperature alloys. They are the most high-strength alloys in high-temperature applications. Generally, these alloys are used in high-temperature environments above 540 °C, and depending on the application, different alloy designs are used. For special corrosion-resistant environments, high-temperature corrosive environments, and equipment requiring high-temperature mechanical strength, including in aerospace, energy, petrochemical industries or special electronics/photovoltaics, Ni-Cr alloys are generally called Inconel alloys, which are common. The nickel-based (heat-resistant) alloy can be mainly used under oxidizing medium conditions, and if a precipitation strengthening element is added to Inconel, a precipitation hardening type nickel-based alloy can be formed, and good mechanical strength and corrosion resistance are maintained at high temperatures. Therefore, the components used in the jet engine, such as Alloy In718, have excellent mechanical strength, good processability, weldability, and moderate cost. Therefore, the current advanced turbine engine is resistant to high temperatures (below 650 ° C). One of the most widely used materials on components.

Increasing the strength of the nickel-based alloy can be achieved by improving the alloy composition, for example, increasing the content of specific alloying elements (Ti, Al, Nb, Cr, C, etc.) can be changed. The microstructure of gold, in turn, changes the mechanical properties of the alloy. Among them, the In718 alloy on the market is mainly strengthened by the precipitation of γ' and γ" phases in the base, and the grain boundary is strengthened by the δ phase and carbide (MC). The effect is that the Laves phase is produced by the segregation of Nb element, which is a brittle harmful phase. The Laves phase should be avoided during the design of the alloy. At the same time, the In718 alloy is added with a certain proportion of Nb elements (4.75~5.50wt). %), can form γ" precipitated phase and strengthen the mechanical properties of In718, but this addition will also form a brittle Laves harmful phase due to Nb segregation, and at the same time cause excessive δ phase formation, resulting in a decrease in mechanical properties.

Therefore, it is extremely necessary in the industry to develop an excellent high-stress nickel-based alloy, which can improve the mechanical properties of the alloy by optimizing the design of the alloy composition, while maintaining good processability, weldability and the like, so that simultaneously It combines mechanical properties and processability to produce a high-stress nickel-based alloy.

In view of the above disadvantages of the prior art, the main object of the present invention is to provide a high stress equiaxed nickel base alloy, integrating a vacuum melting, a vacuum casting and the addition of appropriate elements to prepare a high stress equiaxed nickel base. alloy.

In order to achieve the above object, according to one aspect of the present invention, there is provided a high stress nickel-based alloy having the following composition in terms of weight percent: Ni is 50.0 to 56.0% by weight, Cr is 18.0 to 20.0% by weight, and Nb is 4.0. ~5.5wt%, Mo is 2.8~3.3wt%, Al is 1.3~1.6wt%, Ti is 0.6~0.8 Wt%, the rest consists of Fe and unavoidable impurities.

The high-stress nickel-based alloy is smelted in a vacuum induction furnace, and then vacuum-precision casting is performed in a vacuum environment, and the molten alloy liquid is poured into the ceramic mold, and then cooling is performed to complete the ingot working of the nickel-based alloy.

The above-mentioned nickel-based alloy ingot is subjected to a further heat treatment process; the nickel-based alloy is subjected to a three-stage heat treatment in the present invention, wherein the first-stage heat treatment heat-treats the nickel-based alloy ingot at 1000-1200 ° C After more than two hours, the nickel-based alloy is cooled and cooled by an inert gas (for example, argon); the second-stage heat treatment heats the nickel-based alloy ingot at 900-1000 ° C for at least one hour, and then The nickel-based alloy is cooled and cooled by an inert gas such as argon; the third stage is heat-treated at 700-800 ° C for eight to nine hours, followed by furnace cooling to 600 The temperature is maintained at -650 ° C for eight to nine hours, and then the nickel-based alloy is cooled and quenched with an inert gas (for example, argon gas) to prepare a high-stress nickel-based alloy.

The high-stress nickel-based alloy of the present invention may further comprise a W element, wherein the W is <2.0% by weight; the high-stress nickel-based alloy of the present invention may further comprise a Ta element, wherein the Ta is <2.0wt %.

The above summary and the following detailed description are intended to further illustrate the manner, means and effects of the present invention to achieve the intended purpose. Other purposes and advantages of this creation will be explained in the following description and drawings.

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can readily understand the advantages and effects of the present invention from the disclosure of the present disclosure.

The alloy design of the invention is based on the In718 nickel-based alloy. By adjusting the Al and Ti contents in the alloy, the ratio of the γ' precipitation strengthening phase of Ni3 (Al, Ti) in the nickel-based alloy is increased, and the excessive δ phase is reduced. Precipitation to strengthen the mechanical strength of nickel-based alloys, because the γ' phase is an L12 ordered FCC structure, which is a high-temperature stable phase. Unlike ordinary metals, the mechanical strength decreases with temperature, and its mechanical strength is proportional to temperature, and the higher the temperature. The better the characteristics, although the increase of Al and Ti content can be the number of γ' phase, but if the number of γ' phase is too much, it will cause the alloy brittleness to increase, which is easy to cause the alloy to be brittle and cracked during the casting process or use. In the present invention, the optimum content of Al in the nickel-based alloy should be between 1.3 and 1.6 wt%, and the content of Ti should be between 0.6 and 0.8 wt%.

The Nb element is an important precipitation strengthening element in the alloy of the present invention, and an appropriate amount of Nb element can form a γ" and δ phase of Ni3Nb with Ni, thereby enhancing the mechanical strength of the alloy, wherein the γ" phase is a BCT structure; the δ phase is an orthorhombic structure. Both of them have poor high temperature stability, so excessive precipitation causes mechanical decline. In addition, excessive addition of Nb makes Nb easily segregate with other alloying elements to form Laves phase ((Ni, Fe, Cr) 2 (Mo , Nb, Ti)), which also causes a decrease in mechanical strength, so the optimum Nb content of the nickel-based alloy in the present invention It should be between 4.0 and 5.5 wt%.

Ta is a precipitation strengthening element, which can replace part of Nb to form a γ" phase. The compensation is to reduce the amount of Nb added to avoid the formation of Laves phase, so as to increase the strength of the alloy, but the addition of Ta element is too large, and it is easy to produce coarse TaC type carbide. The type carbide is likely to be the origin of the fracture crack, and the strength of the alloy is lowered. Therefore, the Ta element content of the nickel-based alloy in the present invention is controlled to be <2.0 wt.%.

In the present invention, Mo can increase the γ' phase stable temperature, that is, increase the dissolution temperature of the γ' phase, but excessive Mo content also promotes the formation of a TCP (Topologically-closed-packed) phase and a large-sized bulk carbonized phase. The problem is that the TCP phase is a very brittle phase, which is easy to cause stress concentration due to the accumulation of differential discharge, which causes the material to be weakened. In addition, the formation of the TCP phase consumes a large amount of solid solution strengthening in the γ base. The element causes the strength of the γ base to decrease, so the Mo element content of the nickel-based alloy in the present invention is controlled to be 2.8 to 3.3 wt.%.

W is a solid solution strengthening element in the present invention. The solid solution strengthening in a general alloy is mainly to improve the bonding force between atoms, generate lattice distortion (Lattice Distortion), and reduce the diffusion ability of elements in a solid solution. Strengthen the purpose of the alloy base. It has been found that the W content can not be increased without limit. If the content is too high, the composition will be unevenly distributed, and a serious point will form a harmful phase of TCP in the alloy, resulting in a decrease in the strength of the alloy. Therefore, in order to improve the W element content of the nickel-based alloy of the present invention, it is controlled to be <2.0 wt.%.

According to the foregoing experimental results, the present invention develops a high stress nickel The base alloy has a chemical composition (in terms of weight percent): Ni is 50.0 to 56.0 wt%, Cr is 18.0 to 20.0 wt%, Nb is 4.0 to 5.5 wt%, Mo is 2.8 to 3.3 wt%, and Al is 1.3. 1.6 wt%, Ti is 0.6-0.8 wt%, and the rest is composed of Fe and unavoidable impurities; the invention according to various embodiments may further comprise a Ta element, wherein the Ta is <2.0 wt%, or A W element may be included, wherein the W is <2.0 wt%.

Embodiment 1

The nickel-based superalloy of the present invention is smelted in a vacuum induction furnace according to its chemical composition ratio, and then vacuum-precision casting is performed, and the molten alloy liquid is poured into the ceramic mold, and the alloy sample is prepared to ensure the composition is correct and simultaneously sampled. The components were analyzed by SPARK-AES and the results (in weight percent) are shown in Table 1: The nickel-based superalloy is subjected to heat treatment after casting to optimize the microstructure inside the alloy. The heat treatment procedure is: (1) vacuum homogenization heat treatment: after 1093 ° C / 1 h, quenching with argon to room temperature, (2) Vacuum solution heat treatment: 954-982 ° C / 1 h, quenched with argon to room temperature, (3) vacuum aging heat treatment: 718 ° C / 8 h, the furnace is cooled to 621 ° C and then held for 8 h, then quenched with argon gas until Room temperature. The test rod is subjected to room temperature tensile test after heat treatment, and the test results are shown in Table 2:

Embodiment 2

The nickel-based alloy of the present invention is smelted in a vacuum induction furnace according to its chemical composition ratio, and then vacuum-precision casting is performed, and the molten alloy liquid is poured into the ceramic mold, and the composition of the alloy sample is prepared to ensure the composition is correct and simultaneously sampled. The composition analysis was performed by SPARK-AES, and the results (in weight percentage) are shown in Table 3: The nickel-based superalloy is subjected to heat treatment after casting to optimize the microstructure inside the alloy. The heat treatment procedure is: (1) vacuum homogenization heat treatment: after 1093 ° C / 1 h, quenching with argon to room temperature, (2) Vacuum solution heat treatment: 954-982 ° C / 1 h, quenched with argon to room temperature, (3) vacuum aging heat treatment: 718 ° C / 8 h, the furnace is cooled to 621 ° C and then held for 8 h, then quenched with argon gas until Room temperature. The test rod was subjected to room temperature tensile test after heat treatment, and the test results are shown in Table 4:

Embodiment 3

The nickel-based alloy of the present invention is smelted in a vacuum induction furnace according to its chemical composition ratio, and then vacuum-precision casting is performed, and the molten alloy liquid is poured into the ceramic mold, and the composition of the alloy sample is prepared to ensure the composition is correct and simultaneously sampled. The composition analysis was carried out by SPARK-AES, and the results (in weight percentage) are shown in Table 5. The nickel-based superalloy is subjected to heat treatment after casting to optimize the microstructure inside the alloy. The heat treatment procedure is: (1) vacuum homogenization heat treatment: after 1093 ° C / 1 h, quenching with argon to room temperature, (2) Vacuum solution heat treatment: 954-982 ° C / 1 h, quenched with argon to room temperature, (3) vacuum aging heat treatment: 718 ° C / 8 h, the furnace is cooled to 621 ° C and then held for 8 h, then quenched with argon gas until Room temperature. The test rod was subjected to a room temperature tensile test after heat treatment, and the test results are shown in Table 6:

At present, the most commonly used equiaxed nickel-base superalloys are mainly alloys such as Mar-M247, In713LC and In718. Among them, the production cost of In718 alloy is the lowest, so the invention uses In718 alloy as a comparative reference, and refers to In718 alloy. The AMS 5383E aeronautical material specification is used as a benchmark for room temperature mechanical properties. The relevant room temperature mechanical properties data are listed in Table 7. The room temperature tensile properties of the alloy of the present invention and the In718 alloy are compared to show that the alloy of the present invention is stretched at maximum. Both the strength UTS and the drop strength YS are significantly better than the commercial specification In718, and the elongation is also significantly larger than the commercial specification, showing that the composition is optimized by the present invention. Designed to increase the room temperature mechanical strength and ductility of the optimized In718.

The above-described embodiments are merely illustrative of the features and functions of the present invention and are not intended to limit the scope of the technical content of the present invention. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the creation. Therefore, the scope of protection of this creation should be as listed in the scope of the patent application described later.

Claims (4)

A method for preparing a high-stress nickel-based alloy, the method comprising the steps of: providing a substrate having a Ni of 50.0 to 56.0 wt%, a Cr of 18.0 to 20.0 wt%, a Nb of 4.0 to 5.5 wt%, and Mo 2.8~3.3wt%, Al is 1.3~1.6wt%, Ti is 0.6~0.8wt%, and the rest is composed of Fe and unavoidable impurities; the substrate is smelted in a vacuum induction furnace, and the substrate is smelted After the casting process, the substrate is subjected to a three-stage heat treatment after casting, and the first-stage heat treatment is performed at a temperature range of 1000-1200 ° C, and the second-stage heat treatment is performed at a temperature range of 900-1000 ° C. In the heat treatment, the third-stage heat treatment is first performed by heat treatment at a temperature range of 700-800 ° C, and then cooled to 600-650 ° C to prepare a high-stress nickel-based alloy; wherein the maximum tensile strength of the high-stress nickel-based alloy ( UTS) is greater than 980 MPa. The method for preparing a high-stress nickel-based alloy according to claim 1, wherein the three-stage heat treatment is to cool the high-stress nickel-base alloy by an inert gas. The method for preparing a high-stress nickel-based alloy according to claim 1, wherein the substrate further comprises a Ta element, and the Ta is <2.0 wt%, and the maximum tensile strength of the high-stress nickel-based alloy ( UTS) is greater than 1010 MPa. The method for preparing a high-stress nickel-based alloy according to claim 1, wherein the substrate further comprises a W element, and the W is <2.0% by weight, and the maximum tensile strength of the high-stress nickel-based alloy ( UTS) is greater than 1000 MPa.