JP2015504487A - Nickel-base alloy heat treatment, nickel-base alloy, and articles containing nickel-base alloy - Google Patents

Abstract

The method of heat-treating a 718 type nickel base alloy includes heating the 718 type nickel base alloy to a heat treatment temperature, δ phase grain boundary precipitates at or near the equilibrium concentration in the nickel base alloy, and a total of up to 25 weight percent. Maintaining the alloy at a heat treatment temperature for a heat treatment time sufficient to form a γ ′ phase and a γ ″ phase of the 718-type nickel-base alloy. Also included is a 718-type nickel-base alloy that includes δ phase grain boundary precipitates and a total of up to 25 weight percent γ ′ and γ ″ phase precipitates. Alloys according to the present disclosure may be included in manufactured articles such as face plates, honeycomb core elements, and honeycomb panels of thermal protection systems for supersonic and space vehicles, for example. [Selection] Figure 4

Description

  Embodiments of the present invention generally relate to a method of heat treating a nickel-base alloy.

Alloy 718 (UNS 07718) is one of the most widely used nickel-based alloys and is generally described in US Pat. No. 3,046,108, the specification of which is incorporated herein by reference. The entirety is incorporated herein. Alloy 718 contains elemental composition plus inevitable impurities within the ranges shown in the following table.

  The wide use of alloy 718 is due, at least in part, to some beneficial properties of the alloy. For example, alloy 718 has high strength and stress rupture properties of up to about 1200 ° F. (648.9 ° C.). In addition, alloy 718 has good workability characteristics such as suitable malleability and hot workability and good weldability. Because of these properties, components made from alloy 718 are easy to assemble and, if necessary, these components can be repaired. As noted above, some of the preferred properties of alloy 718 stem from the precipitation hardened microstructure of the alloy, which is primarily strengthened by γ ″ phase precipitates.

The precipitation hardened nickel base alloy includes two main strengthening phases: a γ ′ phase (or “gamma prime”) precipitate and a γ ″ phase (or “gamma double prime”) precipitate. Both the γ ′ and γ ″ phases are stoichiometric nickel-rich intermetallics. However, the γ ′ phase typically has aluminum and titanium (ie, Ni ₃ ( Al, Ti)), while the γ ″ phase contains mainly niobium (ie, Ni ₃ Nb). Both the γ ′ phase and the γ ″ phase form matched precipitates in the face-centered cubic austenite matrix, but the incompatible strain energy associated with the γ ″ phase precipitate (having a body-centered tetragonal crystal structure) is γ Because it is larger than the 'phase precipitate (having a face-centered cubic crystal structure), the γ "phase precipitate tends to be a more effective toughening agent than the γ' phase precipitate. For the same diameter, nickel-base alloys reinforced primarily by γ ″ phase precipitates are generally stronger than nickel-base alloys reinforced primarily by γ ′ phase precipitates.

One of the disadvantages of nickel-base alloys containing a γ ″ phase precipitate reinforced microstructure is that the γ ″ phase is unstable at temperatures above about 1200 ° F. (648.9 ° C.) and the more stable δ phase. (Or “delta phase”). The δ phase precipitate has the same composition as the γ ″ phase precipitate (ie, Ni ₃ Nb), but the δ phase precipitate has an orthorhombic structure and is incompatible with the austenite matrix. The strengthening action of the above δ phase precipitates is generally considered negligible, and as a result of the conversion to δ phase, some mechanical properties of alloy 718 such as stress rupture life are about 1200 ° F. (648). Therefore, the use of alloy 718 has typically been limited to applications where the alloy is exposed to temperatures below 1200 ° F. (648.9 ° C.). .

  In order to form the desired precipitation hardened microstructure, the nickel base alloy is subjected to a heat treatment or precipitation hardening process. The precipitation hardening process of nickel-based alloys generally involves the alloy being at a temperature sufficient to dissolve substantially all γ 'and γ "phase precipitates in the alloy (ie, near the solvus temperature of the precipitates). , At or above that temperature), cooling the alloy from solution processing temperature, followed by solution processing by aging the alloy in one or more aging steps. Is carried out at a temperature below the solvus temperature of the gamma precipitate in order to develop in a controlled manner.

  The development of the desired microstructure in the nickel-base alloy depends on both the alloy composition and the precipitation hardening process employed (ie, solution processing and aging processes). For example, a typical precipitation hardening procedure for high temperature condition alloy 718 is to process the alloy at a temperature of 1750 ° F. (954.4 ° C.) for 1-2 hours, air cool the alloy, and then subject the alloy to two-stage aging. With aging in the process. The first aging step heats the alloy for 8 hours at a first aging temperature of 1325 ° F. (718.3 ° C.) and the alloy is about 50-100 ° F. per hour (28-55.6 ° C. per hour). ) With a second aging temperature of 1150 ° F. (621.2 ° C.) and aging the alloy at the second aging temperature for 8 hours. The alloy is then air cooled to room temperature. The precipitation hardened microstructure resulting from the heat treatment described above is composed of distinct γ 'and γ "phase precipitates, but is mainly strengthened by γ" phase precipitates, and small amounts of γ' phase precipitates are It plays a secondary strengthening role.

  In order to increase the allowable practical temperature of nickel-base alloys, several nickel-base alloys with reinforced γ 'phases have been developed. An example of such an alloy is the Waspaloy nickel base alloy (UNS N07001) commercially available from ATI Allvac, Monroe, North Carolina USA as an ATI Waspaloy alloy. Because the Waspalo nickel-base alloy contains higher levels of alloying elements such as nickel, cobalt, and molybdenum than the alloy 718, the Waspalo alloy is typically more expensive than the alloy 718. Also, because of the faster precipitation kinetics of γ ′ phase precipitates than γ ″ phase precipitates, the Waspaloy alloy is generally considered inferior to alloy 718 in hot workability and weldability.

  Another γ 'phase strengthened nickel base alloy is the ATI 718Plus® alloy commercially available from ATI Allvac, Monroe, NC. ATI 718Plus® is disclosed in US Pat. No. 6,730,264 (“US '264 patent”), which is incorporated herein by reference in its entirety. ATI 718Plus® alloy features a microstructure that is thermally stable in the alloy's aluminum, titanium, and / or niobium levels and relative proportions, and advantageous high temperature mechanical properties such as substantial fracture and creep strength. To be adjusted in a style that provides. Due to the aluminum and titanium content of the ATI 718Plus® alloy along with the niobium content, the alloy is strengthened by the γ ′ and γ ″ phases, the γ ′ phase being the main strengthening phase. Some other nickel-based superalloys Unlike the relatively high titanium / low aluminum composition typical of ATI, the composition of the ATI 718Plus® alloy has a relatively high ratio of atomic percent of aluminum to atomic percent of titanium, which increases thermal stability. The thermal stability properties of the ATI 718Plus® alloy are important for maintaining good mechanical properties such as stress rupture properties after prolonged exposure to high temperatures.

  ATI 718Plus® alloy can undergo processes such as solution annealing, cooling, and aging. A typical heat treatment of an ATI 718Plus® alloy is shown in FIG. 1 as a schematic depiction of a time-temperature heat treatment profile. A typical heat treatment of the ATI 718Plus® alloy is from 1750 ° F. (954.4 ° C.) to 1800 ° F. in order to dissolve any γ ′ and γ ″ phases and precipitate a small amount of δ phase. Solution treatment at a temperature of (982.2 ° C.) The amount of δ phase precipitated is typically less than about half of the low temperature equilibrium content. Precipitation continues at 1450 ° F. (787.8 ° C.) for 2-8 hours, followed by an additional 8 hours at 1300 ° F. (704.4 ° C.) The alloy can be manufactured article or any other desired It may be further processed into a form.

  Additional heat treatments for strengthening the ATI 718Plus® alloy are disclosed in US Pat. Nos. 7,156,932, 7,491,275, and 7,527,702, each of which Which is incorporated herein by reference in its entirety. US Pat. No. 7,531,054 (“US '054 patent”) discloses a heat treatment of ATI 718Plus® alloy, such as direct aging. In the process of the US '054 patent, after hot working an ATI 718 Plus® alloy, the alloy is rapidly and directly cooled to an aging temperature of about 1400 ° F. (760 ° C.) to produce coarse γ ′ phase precipitates. Prevent precipitation. The cooled alloy is aged at the aging temperature or further cooled to room temperature.

  In general, precipitation hardened alloys are not designated for use above their age hardening temperature. Precipitation-hardened nickel alloys can be subject to thermal cycling, where the alloys can be repeatedly exposed to temperatures above their age-hardening temperature and then cooled to temperatures below their age-hardening temperature. It has not been used for certain purposes. As summarized above, conventional age hardening practices for nickel-base alloys have consistent mechanical properties over the practical life of nickel-base alloys that will be subject to thermal cycling where the temperature exceeds the age-hardening temperature of the alloy. Will not bring.

  It would be desirable to provide a heat treatment for precipitation hardened nickel base alloys that provides a robust microstructure and imparts properties that are not significantly affected by thermal cycling. Nickel-based alloys treated in this way may be useful, for example, for use in face plates and honeycomb cores of thermal protection systems for supersonic aircraft, and as materials in other manufactured articles that undergo practical thermal cycling.

  According to one aspect of the present disclosure, a method for heat treating a 718 type nickel base alloy includes heating the 718 type nickel base alloy to a heat treatment temperature, and δ phase grain boundary precipitation at or near equilibrium in the nickel base alloy. Maintaining a 718 type nickel base alloy at a heat treatment temperature for a heat treatment time sufficient to form an article. The heat treatment results in the formation of a total of up to 25 weight percent of γ ′ and γ ″ phase precipitates in the nickel base alloy. After holding the 718 type alloy at the heat treatment temperature for the heat treatment time, the 718 type nickel base alloy Cooled to maintain δ phase grain boundary precipitates in the alloy.

  According to another aspect of the present disclosure, a method for heat treating a nickel-base alloy includes a temperature 20 ° F. (11 ° C.) higher than the nose of the isothermal transformation diagram of delta phase precipitation (“TTT diagram”) to a maximum of the nose of the TTT diagram. Heating the nickel-base alloy to a heat treatment temperature within a heat treatment temperature range of 100 ° F. (55.6 ° C.) and a nickel base within the heat treatment temperature range for a heat treatment time within a range of 30 minutes to 300 minutes. Holding the alloy. After holding the nickel base alloy within the heat treatment temperature range for the heat treatment time, the nickel base alloy is air cooled to ambient temperature. In a non-limiting embodiment, the nickel-base alloy is cooled at a cooling rate that does not exceed 1 ° F. per minute (0.56 ° C. per minute).

  In a non-limiting embodiment, the nickel-base alloy is, by weight percent, 0.01 to 0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004 to 0.020 phosphorus. Up to 0.025 sulfur, 17.00-21.00 chromium, 2.50 up to 3.10 molybdenum, 5.20 up to 5.80 niobium, 0.50 up to 1.00 titanium 1.20 to 1.70 aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003 to 0.008 boron , Nickel, and inevitable impurities.

  According to a further aspect of the present disclosure, a 718 type nickel base alloy comprising nickel, chromium, and iron is provided. Nickel-based alloys are strengthened by niobium and optionally one or more alloying elements of aluminum and titanium, the alloy including an austenitic matrix such as austenite grain boundaries. Equilibrium or near-equilibrium δ phase precipitates are present at austenite grain boundaries in type 718 alloys, and the alloys contain up to 25 weight percent of γ 'phase and γ "precipitates.

  According to a further aspect of the present disclosure, the process of making an article of manufacture includes at least one of the methods disclosed herein. In certain non-limiting embodiments, the process may be suitable for making a manufactured article selected from a face plate of a thermal protection system for a supersonic aircraft, a honeycomb core, and a honeycomb panel.

  According to yet another aspect of the present disclosure, an article of manufacture includes an alloy disclosed herein. Such an article of manufacture can be selected from, but not limited to, a face plate of a thermal protection system for a supersonic aircraft, a honeycomb core, and a honeycomb panel.

  The features and advantages of the alloys and methods described herein may be better understood with reference to the accompanying drawings.

1 is a temperature-time heat treatment diagram of a conventional prior art heat treatment for strengthening a nickel-base alloy. FIG. 1 is a schematic depiction of an example metal thermal protection system. 1 is a schematic depiction of an example of a honeycomb comb panel. 1 is a schematic depiction of an exploded view of an example of a honeycomb comb panel. 3 is a flow diagram of a non-limiting embodiment of a heat treatment of a nickel-base alloy according to the present disclosure. It is a constant temperature transformation curve of an alloy 718 nickel base superalloy. It is an isothermal transformation curve of ATI 718Plus (trademark) alloy. 2 is a schematic temperature-time plot of a non-limiting embodiment of a method according to the present disclosure for heat treating a nickel-based alloy. 2 is a schematic depiction of thermal cycling used to evaluate a non-limiting embodiment of a method for heat treating a nickel-based alloy according to the present disclosure. Provided are plots of ultimate tensile strength as a function of the number of thermal cycles of ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure, 1650 ° F. (898.9 ° C.) and 1550 ° Comparison with conventional γ ′ / γ ”heat treatment methods before and after thermal cycling to F (843.3 ° C.). 1650 provides a plot of relatively maintained ultimate tensile strength as a function of the number of thermal cycles of an ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure, .9 ° C.) and 1550 ° F. (843.3 ° C.) before and after thermal cycling and compared to conventional γ ′ / γ ″ heat treatment methods. Provided are plots of yield strength as a function of the number of thermal cycles of ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure, 1650 ° F. (898.9 ° C.) and 1550 ° F. Comparison was made with a conventional γ ′ / γ ”heat treatment method before and after thermal cycling to (843.3 ° C.). 1650 ° F. (898.9), including a plot of the relative sustained yield strength as a function of the number of thermal cycles of the ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure. ° C) and 1550 ° F (843.3 ° C) before and after thermal cycling and compared to conventional γ '/ γ "heat treatment methods. Includes plots of elongation as a function of the number of thermal cycles of ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure, including 1650 ° F. (898.9 ° C.) and 1550 ° F. ( Compared to the conventional γ ′ / γ ”heat treatment method before and after thermal cycling to 843.3 ° C.). Includes plots of relative elongation as a function of number of thermal cycles for ATI 718Plus® alloy treated with a non-limiting heat treatment method according to the present disclosure, including 1650 ° F. (898.9 ° C.) and 1550 ° Comparison with conventional γ ′ / γ ”heat treatment methods before and after thermal cycling to F (843.3 ° C.). Includes a plot of ultimate tensile strength as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure, prior to thermal cycling to 1650 ° F. (898.9 ° C.) and It was compared with the later conventional γ ′ / γ ”heat treatment method. Including a plot of the relative sustained ultimate tensile strength as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure, to 1650 ° F. (898.9 ° C.) Compared with conventional γ ′ / γ ”heat treatment method before and after thermal cycling. Conventional plots of yield strength as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure, prior to and after thermal cycling to 1650 ° F. (898.9 ° C.) Compared with the γ ′ / γ ”heat treatment method. Heat plots to 1650 ° F. (898.9 ° C.), including a plot of the relative sustained yield strength as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure. Comparison with conventional γ '/ γ "heat treatment method before and after circulation. Conventional plots before and after thermal cycling to 1650 ° F. (898.9 ° C.), including a plot of elongation as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure. Compared with the γ ′ / γ ”heat treatment method. Includes plots of relative elongation as a function of the number of thermal cycles of alloy 718 treated with a non-limiting heat treatment method according to the present disclosure, before and after thermal cycling to 1650 ° F. (898.9 ° C.). In comparison with the conventional γ ′ / γ ”heat treatment method. 2 is a dark field optical micrograph of a surface area of an ATI 718Plus® alloy sheet heat treated according to a non-limiting embodiment of the present disclosure. 1650 ° F. (898.9 ° C.) from ambient temperature and surface area of ATI 718Plus® alloy sheet heat treated according to a non-limiting embodiment of the present disclosure after 5 thermal cycles back to ambient temperature It is a dark-field optical micrograph. It is a dark-field optical microscope photograph of the surface area | region of the ATI 718Plus (trademark) alloy sheet heat-processed by the conventional (gamma) '/ (gamma) "heat processing. Of surface area of ATI 718Plus® alloy sheet heat treated by conventional γ ′ / γ ”heat treatment after 5 thermal cycles from ambient temperature to 1650 ° F. (898.9 ° C.) and back to ambient temperature It is a dark-field optical micrograph. 2 is a dark field optical micrograph of a surface area of an ATI 718Plus® alloy sheet heat treated according to a non-limiting embodiment of the present disclosure. Of surface area of ATI 718Plus® alloy sheet heat treated according to a non-limiting embodiment of the present disclosure after 5 thermal cycles from ambient temperature to 1550 ° F. (843.3 ° C.) and back to ambient temperature It is a dark-field optical micrograph. It is a dark-field optical microscope photograph of the surface area | region of the ATI 718Plus (trademark) alloy sheet heat-processed by the conventional (gamma) '/ (gamma) "heat processing. Darkness of surface area of ATI 718Plus® alloy sheet heat treated by conventional γ ′ / γ ”heat treatment after 5 thermal cycles from ambient temperature to 1550 ° F. (843.3 ° C.) and back to ambient temperature It is a field optical microscope photograph. 2 is a dark field optical micrograph of a surface region of an alloy 718 sheet heat treated according to a non-limiting embodiment of the present disclosure. Dark field optical micrograph of the surface area of alloy 718 sheet heat treated according to a non-limiting embodiment of the present disclosure after 5 thermal cycles from ambient temperature to 1650 ° F. (898.9 ° C.) and back to ambient temperature It is. It is a dark-field optical micrograph of the surface area | region of the alloy 718 sheet | seat heat-processed by the conventional gamma '/ gamma "heat processing. Dark field optical micrograph of surface area of alloy 718 sheet heat treated by conventional γ ′ / γ ”heat treatment after 5 thermal cycles from ambient temperature to 1650 ° F. (898.9 ° C.) and back to ambient temperature It is.

  The reader will understand the foregoing details, as well as others, in light of the following detailed description of certain non-limiting embodiments according to the present disclosure.

  In this description of non-limiting embodiments, unless an operational example is described or described, it is understood that in all cases all numbers representing quantities or features are modified by the term “about”. At a minimum, and not an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter is at least taken into account the reported significant digits and by applying normal rounding techniques Should be interpreted.

  Any patents, publications, or other disclosure materials that are mentioned to be incorporated in whole or in part by reference are intended to be incorporated into the existing definitions, descriptions, or other disclosures described in this disclosure. Incorporated herein to the extent that it does not conflict with the disclosure material. As such, and to the extent necessary, the disclosure set forth herein supersedes any conflicting material that is incorporated herein by reference. Any material or portions thereof that are referenced to be incorporated herein by reference, but that conflict with existing definitions, descriptions, or other disclosure material described in this disclosure, It is incorporated only to the extent that no contradiction arises with the disclosed material.

  Certain nickel-based alloys are contemplated for use as the faceplate and core elements of honeycomb panels used in thermal protection systems for supersonic aircraft. The surface temperature of a supersonic vehicle circulates between ground temperature and about 2200 ° F. (1204 ° C.) at least once in a single flight mission in practical use. Exposure of such age-hardened nickel-base alloys to such thermal cycling is related to volume fractions when brazed of nickel-base alloys before flying to the first flight mission and compared to age-hardened conditions. Rate and the size of the precipitated phase, especially the γ ′ and γ ″ phase precipitates. Further, different flight missions are expected to have different thermal exposure profiles, resulting in Based on multiple missions, the microstructure and mechanical properties of age hardened nickel base alloys vary.

  Thermal protection system (TPS) protects the main components of supersonic vehicles and spacecraft from melting or otherwise being damaged from heat generated during high speed and / or reentry into the atmosphere . TPS must be lightweight, reusable, and maintainable. A schematic depiction of an example of a metal TPS (10) employing a honeycomb panel is represented in FIG. The metal TPS (10) may be secured to an external reinforcement member (12) of a component, such as a supersonic vehicle or a spacecraft cryogenic fuel tank (not shown). The metal TPS (10) can include, for example, a metal honeycomb panel (14) and a foil encapsulating insulator (16).

  An example of the honeycomb panel (20) is schematically shown in FIG. 3A, and an exploded schematic view of the honeycomb panel (20) is shown in FIG. 3B. The honeycomb panel (20) includes a segmented honeycomb core (22) interposed between and bonded to opposing face plates (24), thereby providing a plurality of sealed chambers within the panel. As used herein, the term “honeycomb panel” refers to a metal honeycomb core that is interposed between or sandwiched between metal surface plates. As used herein, the terms “honeycomb” and “honeycomb core” are formed from an alloy foil and are interposed between two metal or other suitable material faceplates to provide a honeycomb panel. Or it refers to a manufactured product comprising an array of substantially polygonal (eg hexagonal) cells that can be applied as a core material to be sandwiched. As used herein, the term “surface plate” refers to a metal foil, sheet, or panel that is generally joined to the metal honeycomb core shown in FIG. 2 to provide a honeycomb panel. Honeycomb cores are used to form honeycomb panels by adhesively bonding, brazing, welding, or otherwise joining the face plates to the open cells of the honeycomb core. Honeycomb panels exhibit high compression and shear properties while minimizing the weight required to achieve these properties as compared to monolithic materials. Honeycomb panels are used in aerospace, marine, and ground transportation applications to reduce vehicle weight and reduce fuel consumption. Methods for forming honeycomb cores, face plates, and honeycomb panels are well known to those skilled in the art and are therefore not further described herein.

  The aerospace industry has seriously considered the use of metal TPS for only the last 15 years, and little attention has been paid to the alloys used for the faceplates and honeycomb cores of aerospace panels. In general, due to the inherent phase instability of the microstructure of precipitation hardened alloys, precipitation hardened alloys are avoided, and solution strengthened or oxide dispersion strengthened alloys have been used for TPS applications.

  One non-limiting embodiment of the present invention is directed to a method of heat treating a nickel-base alloy to provide a microstructure that is generally stable when subjected to thermal cycling. Since the microstructure achieved by the method remains substantially the same during one or more thermal cycles experienced by the nickel-base alloy, the mechanical properties of the nickel-base alloy are determined by the thermal and specific characteristics of the alloy. At a certain temperature, it remains substantially the same. For example, a non-limiting embodiment of a heat treatment method according to the present disclosure has the property of being 1550 ° F. (843.3 ° C.) of the second thermal cycle, which is 1550 ° F. (843 ° C. of the 10th thermal cycle). .3 ° C) is substantially the same as the properties of the same nickel-base alloy, but for example the mechanical properties of the nickel-base alloy at 1650 ° F (898.9 ° C) or 1700 ° F (926.7 ° C) Provides a nickel-base alloy that is not the same.

  It has been determined that the γ ′ phase has little effect on the strength of low γ ′ phase volume fraction alloys, such as alloy 718, for example, at temperatures above about 1500 ° F. (815.6 ° C.). Therefore, heat treatments designed to optimize the γ 'phase are beneficial for applications such as supersonic air vehicles TPS that repeatedly undergo thermal cycling between ambient and temperatures up to 2200 ° F (1204 ° C). It was confirmed that it was not. Such a heat treatment that provides a stable microstructure during thermal cycling would be beneficial for use in a thermal protection system.

  For example, a non-limiting embodiment according to the present disclosure can provide heat between ambient ground temperature and a maximum temperature of about 1450 ° F. (787.8 ° C.) to about 75 ° F. (42 ° C.) below the δ solvus temperature. In order to produce a thermally stable microstructure in a 718 nickel-base alloy that can withstand circulation, a method of heat treating the nickel-base alloy is targeted. The thermally stable microstructure is a temperature between ambient temperature and a maximum temperature in the range of about 1450 ° F. (787.8 ° C.) to about 75 ° F. (42 ° C.) below the δ solvus temperature of the alloy. A microstructure that provides the alloy with substantially unchanged mechanical properties when exposed to a range of thermal cycles. Exposure of nickel-based alloys to temperatures above the heat treatment temperature range according to the present disclosure can cause deleterious changes in the microstructure and mechanical properties of the alloys.

  The δ solvus temperature of alloy 718 is about 1881 ° F. (1027 ° C.). The δ solvus temperature of the ATI 718Plus® alloy is about 1840 ° F. (1004 ° C.). The δ solvus temperatures of other nickel-based alloys are known or can be readily determined by those skilled in the metallurgy art without undue experimentation.

  In a non-limiting embodiment according to the present disclosure, the method provides an equilibrium temperature or near equilibrium concentration of grain boundary δ phase at the austenite matrix grain boundaries, for a total of up to 25 weight percent γ ′ and γ ″ phase precipitation. In view of the precipitation of grain boundary δ phase at or near the equilibrium concentration in the embodiment according to the present disclosure, the embodiment of the heat treatment method according to the present disclosure is referred to herein as “δ phase heat treatment”. Is done.

  Embodiments of the δ phase heat treatment according to the present disclosure provide a volume fraction of δ phase that does not substantially decrease until the operating temperature exceeds about 75 ° F. (42 ° C.) below the δ solvus temperature. Thus, the δ phase heat treatment embodiment disclosed herein promotes a stable microstructure for applications where the temperature may circulate to a maximum temperature of about 75 ° F. (42 ° C.) below the δ solvus temperature. To do. The δ phase precipitated at the grain boundaries by the method of the present disclosure also serves the purpose of preventing grain growth and further stabilizes the microstructure. The δ phase heat treatment embodiments disclosed herein provide low strength in nickel-base alloys below about 1500 ° F. (815.6 ° C.). However, by comparison, a conventional heat treated 718-type nickel-base alloy part that is exposed to temperatures in practical use above about 1500 ° F. (815.6 ° C.) is only 1500 for the first thermal cycle to which the part is exposed. It will exhibit relatively high strength at temperatures below ° F (815.6 ° C).

  While not limited herein, embodiments of the δ-phase heat treatment disclosed herein may be used in conjunction with nickel-base alloy compositions containing niobium (Nb), including 718-type nickel-base alloys and derivatives thereof. Can be used. As used herein, the term “nickel-based alloy” refers to an alloy that includes primarily nickel, along with one or more other alloying elements and inevitable impurities. As used herein, the term “718-type nickel-base alloy” means a nickel-base alloy, as defined herein, and includes nickel, chromium, iron, reinforcing additive elements along with unavoidable impurities. Contains or consists of some niobium and optionally one or both of aluminum and titanium. Non-limiting examples of 718 type nickel base alloys include alloy 718 and other alloys described below.

  Non-limiting examples of type 718 nickel-base alloys that are believed to be particularly well suited to non-limiting embodiments of heat treatment according to the present disclosure include nickel, chromium, up to 14 weight percent iron, the strengthening additive niobium, optional In addition, an alloy additive element of one or both of aluminum and titanium, and a nickel base alloy containing inevitable impurities. Another non-limiting example of a type 718 nickel-base alloy that is believed to be particularly well suited for non-limiting embodiments of heat treatment according to the present disclosure is chromium, up to 14 weights as defined herein A nickel-based alloy containing percent iron, the strengthening additive element niobium, optionally an alloying element of one or both of aluminum and titanium, and inevitable impurities.

  A further non-limiting example of a 718 type nickel base alloy in which embodiments of the heat treatment method according to the present disclosure can be used is the nickel base alloy disclosed in US Pat. No. 6,730,264 (“the '264 patent”). Yes, this is, in weight percent, 0.1 carbon, 12-20 chromium, up to 4 molybdenum, up to 6 tungsten, 5-12 cobalt, 6-14 iron, 4-8 niobium, 0 Contains, or contains, 2.6-2.6 aluminum, 0.4-1.4 titanium, 0.003-0.03 phosphorus, 0.003-0.015 boron, nickel, and inevitable impurities And the sum of the weight percent of molybdenum and the weight percent of tungsten is at least 2 and does not exceed 8 and is the sum of the atomic percent of aluminum and the atomic percent of titanium. Is between 2 and 6, the ratio of atomic percent of aluminum to atomic percent of titanium is at least 1.5, and the sum of atomic percent of aluminum and atomic percent of titanium divided by atomic percent of niobium Is 0.8 to 1.3. The entire disclosure of US Pat. No. 6,730,264 is incorporated herein by reference.

  Another non-limiting example of a type 718 nickel-base alloy in which embodiments of the heat treatment method according to the present disclosure may be used is the nickel-base alloy disclosed in the US '264 patent, which is 50% by weight. ~ 55 nickel, 17-21 chromium, 2.8-3.3 molybdenum, 4.7 percent to 5.5 niobium, up to 1 cobalt, 0.003-0.015 boron, up to 0. 3 copper, up to 0.08 carbon, up to 0.35 manganese, 0.003-0.03 phosphorous acid, up to 0.015 sulfur, up to 0.35 silicon, iron, aluminum, titanium, And the sum of the atomic percent of aluminum and the atomic percent of titanium is about 2 to about 6 atomic percent, and the atomic percent of aluminum and the The atomic percent ratio of at least about 1.5 and the sum of atomic percent of aluminum plus atomic percent of titanium divided by the atomic percent of niobium is about 0.8 to about 1.3. is there. In certain embodiments of the alloy, the iron weight percent is 12 to up to 20.

  Yet another non-limiting example of a type 718 nickel-base alloy in which embodiments of the heat treatment method according to the present disclosure can be used is ATI 718Plus® alloy (UNS N07818), which is ATI Allvac, Monroe, Nickel-based alloy available from North Carolina, USA, which, by weight, is 17.00 to 21.00 chromium, 2.50 to 3.10 molybdenum, 5.20 to 5.80 niobium, 0.50 to 1.00 titanium, 1.20 to 1.70 aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003-0.008 boron, 0.01-0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.0 Phosphorus from 4 to 0.020, up to 0.025 sulfur, or nickel, and incidental impurities, or consisting of them. Two of AMS 5441 and AMS 5442 for corrosion and heat resistant rods, forgings, and rings are AMS specifications that describe the heat treatment conventionally used by ATI 718Plus® alloy. Each of AMS 5441 and AMS 5442 is incorporated herein by reference in its entirety.

  Another non-limiting example of a 718 type nickel-based alloy in which embodiments of the heat treatment method according to the present disclosure can be used is Alloy 718 (UNS N07718), the composition of which is well known in the industry. In one non-limiting embodiment, alloy 718 is, by weight percent, 50.0-55.0 nickel, 17-21.0 chromium, up to 0.08 carbon, up to 0.35 manganese, up to 0.35 weight percent silicon, 2.8 to 3.3 molybdenum, greater than 0 to up to 5.5 niobium and tantalum (the sum of niobium and tantalum is 4.75 to 5.5); Contains or consists of 65 to 1.15 titanium, 0.20 to 0.8 aluminum, up to 0.006 boron, iron, and inevitable impurities.

  As used herein, the term “mechanical property” refers to a stress-strain relationship that relates to an elastic or inelastic reaction when a force is applied to an alloy, or that occurs when a force is applied to an alloy. Refers to the properties of alloys with Within the meaning of the present disclosure, mechanical properties refer specifically to tensile strength, yield strength, elongation, and stress rupture life. As used herein, the term “thermally stable mechanical properties” means that the alloy repeats thermal cycling between ambient ground temperature and 75 ° F. (41.7 ° C.) below the δ solvus temperature. When received, it refers to the state in which the mechanical properties of the alloy do not change by more than 20%. As used herein, the term “ambient ground temperature” is defined as any ambient temperature caused by a natural land climate at ground level.

  The inventors of the present invention have noted the effect of thermal cycle peak temperature on the degree of degradation of the mechanical properties of nickel-base alloys for a given δ-phase heat treatment according to a non-limiting embodiment of the present disclosure. The selection of the δ phase heat treatment temperature must be selected to match or closely match the expected peak practical temperature of the nickel-base alloy.

  Referring now to FIG. 4, in a non-limiting embodiment according to the present disclosure, a method of subjecting a 718 nickel-base alloy (30) to δ phase heat treatment involves heating the 718 nickel-base alloy to a heat treatment temperature within a heat treatment temperature range. (32) sufficient to form an equilibrium concentration or near equilibrium concentration of δ phase grain boundary precipitates in the nickel base alloy and up to 25 weight percent total γ ′ and γ ″ phases in the nickel base alloy. Maintaining the alloy within the heat treatment temperature range for a long heat treatment time (34) and air cooling the 718 type nickel base alloy (36).

  As used herein, the term “heat treatment temperature” refers to the equilibrium concentration or near equilibrium concentration of δ phase precipitates at grain boundaries of type 718 nickel-base alloy, and up to 25 weight percent γ ′ phase and γ ”overall. As used herein, the term “heat treatment time” is defined as the temperature at which a 718 phase nickel-base alloy grain boundary is present at or near the equilibrium concentration of δ phase precipitates, as well as the overall Means the time sufficient to precipitate up to 25 weight percent of the γ ′ and γ ″ phases. As used herein, the term “equilibrium concentration” refers to a nickel-base alloy or a 718-type nickel-base alloy. Defined by the composition as the maximum concentration of δ phase precipitates that can be formed at the heat treatment temperature. As used herein, the term “near-equilibrium concentration” refers to a state in which a nickel-base alloy includes from about 5 weight percent to about 35 weight percent δ phase at the grain boundaries. In a non-limiting embodiment, after the δ phase heat treatment, the nickel-base alloy can include from about 6 weight percent to about 12 weight percent δ phase precipitated at the grain boundaries. Such a result has been observed to be typical for ATI 718Plus® alloy. In another non-limiting embodiment, after the δ phase heat treatment, the nickel-base alloy can include about 10 weight percent to about 25 weight percent δ phase precipitated at the grain boundaries. Such a result has been observed to be typical for ATI 718Plus® alloy. The amount of δ, γ ′ and γ ″ phases formed during the δ phase heat treatment according to the present disclosure depends to some extent on the specific composition of the nickel-base alloy, and the amount of such phases formed is It will be understood that it can be determined easily by a person skilled in the art and without undue experimentation.

  In a non-limiting embodiment, the heat treatment temperature is from a lower limit 20 ° F. (11 ° C.) higher than the nose of the isothermal transformation diagram (“TTT diagram”) of the δ phase precipitation of a particular nickel-based alloy from the lower limit of a particular TTT diagram. Within the heat treatment temperature range with an upper limit of 100 ° F. (55.6 ° C.) below the nose of phase precipitation. The TTT diagram for a particular nickel-based alloy is a plot of temperature as a function of logarithm of the alloy time. The TTT diagram is used to determine when second phase transformations such as the δ, γ ′, and γ ″ phase transformations begin and end during isothermal heat treatment of previously solution-treated nickel-base alloys. Those skilled in the art will understand that a particular TTT diagram is specific to a particular alloy composition.The TTT diagram of an embodiment of alloy 718 is reproduced in FIG. 5A, and the ATI 718Plus® alloy. These TTT diagrams are reproduced in Fig. 5 B. The δ phase precipitation curves in these TTT diagrams are displayed as "δ (GB)" in Fig. 5A and "δ (grain)" in Fig. 5B. As will be appreciated by those skilled in the art, the “nose” of the δ phase curve is known to those skilled in the art as part of the δ phase curve plotted at the earliest time point on the time axis. For example, the nose of the δ phase curve of FIG. 5A occurs at about 900 ° C. for about 0.045 hours. The nose of the δ phase curve of FIG. 5B occurs at about 900 ° C. for about 0.035 hours. The curves shown in FIGS. 5A and 5B are Xie, et al. , "TTT Diagram of a Newly Developed Nickel-Base Superalloy-Allvac 718Plus (registered trademark), Proceedings: Superalloys 718,625, 706 and Derivatives. Further explanation regarding the use of the TTT diagram is not necessary herein because one of ordinary skill in the art can interpret and use the TTT diagram.In addition, the TTT diagram for a particular nickel-based alloy is Are publicly available or can be generated by one of ordinary skill in the art without undue experimentation.

  With reference to the schematic heat treatment temperature-time profile (40) shown in FIG. 6 and with reference to the method steps generally shown in FIG. 4, a non-limiting method of heat treating a 718 nickel-base alloy according to the present disclosure Embodiments include heating the 718-type nickel-base alloy to a heat treatment temperature within a heat treatment temperature range of 1700 ° F. (926.7 ° C.) to 1725 ° F. (940.6 ° C.) (32). In a non-limiting embodiment of the method, the heated 718-type nickel-base alloy is maintained within the heat treatment temperature range for a heat treatment time of 30 minutes to 300 minutes (34). After holding at the heat treatment temperature for the heat treatment time (34), the 718 type nickel-base alloy is air-cooled and maintains δ phase precipitates at the grain boundaries. According to embodiments of the δ phase heat treatment method disclosed herein, δ phase grain boundary precipitates are formed primarily during the heating step (32) and the holding step (34). For this reason, the heating step (32) and the holding step (34) are collectively referred to as “δ phase aging”.

  In a non-limiting embodiment, after the nickel base alloy is held at the heat treatment temperature for the heat treatment time, the nickel base alloy is air cooled from the heat treatment temperature to ambient temperature. In certain non-limiting embodiments, the nickel-base alloy is cooled at a cooling rate that does not exceed 1 ° F. per minute (0.56 ° C. per minute). Slow cooling is advantageous in certain non-limiting embodiments according to the present disclosure, as some degree of γ 'phase precipitation is possible in nickel based alloys. The small amount of γ 'phase that can precipitate during slow cooling is generally coarse in structure and is therefore more stable with respect to thermal cycling and has less impact on the mechanical properties of the alloy. It is preferred to have a small amount of relatively stable γ 'phase precipitate during slow cooling rather than having uncontrolled γ' phase precipitation during practical thermal cycling.

  Alloys processed by any of the methods disclosed herein can be formed into drawn materials or other manufactured articles. In certain non-limiting embodiments according to the present disclosure, the 718 nickel-base alloy is selected from foils, honeycomb cores, faceplates, and honeycomb panels by methods including method embodiments disclosed herein. Processed into manufactured articles. As used herein, the term “foil” refers to a sheet having a thickness of less than 0.006 inches (0.15 mm) and of any width and length. As a practical matter, the width of the foil is limited by the capacity of the cold rolling equipment used to wind the alloy. In certain non-limiting embodiments of the method according to the present disclosure, alloys fabricated according to the method embodiments of the present disclosure can be up to 18 inches (0.46 m), up to 24 inches (0.61 m), or up to 36 inches. It can be processed into a foil having a width of (0.91 m).

  For applications where the maximum operating temperature to which the alloy is exposed is known and is less than about 1700 ° F. (926.7 ° C.), a non-limiting embodiment of the method according to the present disclosure cools the nickel-base alloy from the heat treatment temperature. It may further comprise stabilizing the heat treatment after the step. In a non-limiting embodiment according to the present disclosure, stabilizing the heat treatment comprises heating the nickel-based alloy to a heat treatment stabilization temperature, and heating the alloy for at least 2 hours, or at least 2 hours up to 4 hours at that temperature. To hold on. In a non-limiting embodiment, the heat treatment stabilization temperature is the maximum practical temperature to which the alloy is exposed and is in the range of 1700 ° F. (926.7 ° C.) or less, or from 1700 ° F. (926.7 ° C.) to Within the range of 1450 ° F. (787.8 ° C.). As used herein, the term “maximum operating temperature” refers to the maximum temperature that a particular nickel-base alloy is expected to experience when the alloy or an article containing the alloy is used for its intended purpose. . After stabilization of the heat treatment according to the present disclosure, the nickel-base alloy is air cooled from the heat treatment stabilization temperature to ambient temperature. In another non-limiting embodiment, the nickel-base alloy is cooled at a cooling rate that does not exceed 1 ° F. per minute (0.56 ° C. per minute) from the heat treatment stabilization temperature to ambient temperature.

  It will be appreciated that the non-limiting embodiments of δ phase heat treatment and δ phase aging according to the present disclosure can be used with any form and shape of a nickel-base alloy or a 718 type nickel-base alloy. Various forms include, but are not limited to, commercially available stretch materials such as rods, rods, plates, sheets, pieces, and extrudates. Non-limiting embodiments of δ-phase heat treatment and δ-phase aging according to the present disclosure may be used for manufactured articles such as, but not limited to, nickel-base alloys or 718-type nickel-base alloys, joints, and the like. Recognize further.

  In a non-limiting embodiment of a method for heat treating a nickel-based alloy according to the present disclosure, the nickel-based alloy is, by weight percent, 17.00-21.00 chromium, 2.50-3.10 molybdenum, 5. 20 to 5.80 niobium, 0.50 to 1.00 titanium, 1.20 to 1.70 aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 008 to 1.40 tungsten, 0.003 to 0.008 boron, 0.01 to 0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004 to 0.020 Contains or consists of phosphorus, up to 0.025 sulfur, nickel, and inevitable impurities. Such non-limiting embodiments include heat treating the nickel base alloy to a heat treatment temperature in the range of 1700 ° F. (926.7 ° C.) to 1725 ° F. (940.6 ° C.), within the nickel base alloy. A heat treatment time in the range of 30 minutes to 300 minutes sufficient to form an equilibrium concentration or near-equilibrium concentration of δ phase grain boundary precipitates and a total of up to 25 weight percent γ ′ and γ ″ phases in the alloy; In the non-limiting embodiment, the nickel-based alloy comprises a foil, a honeycomb core, a face plate, and a honeycomb panel. One of these.

  A non-limiting aspect according to the present disclosure is directed to a type 718 nickel-base alloy, the term of which is defined herein, which includes an austenitic matrix containing grain boundaries. Equilibrium concentration or near-equilibrium concentration δ phase precipitates are present at grain boundaries, and a total of up to 25 weight percent γ 'and γ "phases are present in the alloy.

  One specific, non-limiting embodiment of a 718 type nickel-based alloy according to the present disclosure includes an austenitic matrix including grain boundaries, a δ phase precipitate at or near equilibrium concentration at the grain boundaries, up to a total of 25 weight percent Γ ′ and γ ″ phase precipitates, and up to 14 weight percent iron. Another non-limiting example of a 718 type nickel-based alloy according to the present disclosure includes an austenitic matrix including grain boundaries, grain boundaries Contains δ phase precipitates at or near equilibrium concentration, up to a total of 25 weight percent γ ′ and γ ″ phase precipitates, and from 6 weight percent up to 14 weight percent iron.

  Another specific, non-limiting example of a 718 type nickel-based alloy according to the present disclosure includes an austenite matrix that includes grain boundaries, a near-equilibrium concentration δ phase precipitate at the grain boundaries, and a total of up to 25 weight percent γ ′ phase. And γ ″ phase precipitates. The alloy is, by weight percent, 0.1 carbon, 12-20 chromium, up to 4 molybdenum, up to 6 tungsten, 5-12 cobalt, 6-14 iron, 4-8 niobium, 0.6-2.6 aluminum, 0.4-1.4 titanium, 0.003-0.03 phosphorus, 0.003-0.015 boron, nickel, and inevitable Further comprising or consisting of impurities, the sum of the weight percent of molybdenum and the weight percent of tungsten is at least 2 and does not exceed 8, and the atomic percent of aluminum and the The sum of atomic percent of titanium is 2-6, the ratio of atomic percent of aluminum to atomic percent of titanium is at least 1.5, and the sum of atomic percent of aluminum and atomic percent of titanium is the niobium Divided by atomic percent of 0.8 to 1.3.

  Yet another specific, non-limiting example of a 718 type nickel-based alloy according to the present disclosure includes an austenitic matrix including grain boundaries, a near-equilibrium concentration δ phase precipitate at the grain boundaries, and a total of up to 25 weight percent γ ′. Phase and γ ″ phase precipitates. The alloy has, in weight percent, 0 to about 0.08 carbon, 0 to about 0.35 manganese, about 0.003 to about 0.03 phosphorous acid, 0 About 0.015 sulfur, 0 to about 0.35 silicon, about 17 to about 21 chromium, about 50 to about 55 nickel, about 2.8 to up to about 3.3 molybdenum, about 4.7 Percent to about 5.5 niobium, 0 to about 1 cobalt, about 0.003 to about 0.015 boron, 0 to about 0.3 copper, and residual iron (typically about 12 to about 20 Percent), aluminum, titanium, and inevitable impurities Or the sum of atomic percent of aluminum and atomic percent of titanium is about 2 to about 6 percent, and the ratio of atomic percent of aluminum to atomic percent of titanium is at least about 1.5 The sum of the atomic percent of aluminum + titanium divided by the atomic percent of niobium is equal to about 0.8 to about 1.3.

  Further specific, non-limiting examples of Type 718 nickel-base alloys according to the present disclosure include an austenitic matrix including grain boundaries, a near-equilibrium concentration δ phase precipitate at the grain boundaries, and a total of up to 25 weight percent γ ′ phase and γ ″ phase precipitates are included. Alloys are in weight percent from 0.01 to 0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004 to 0.020 phosphorus, up to 0.025 sulfur, 17.00-21.00 chromium, 2.50-3.10 molybdenum, 5.20-5.80 niobium, 0.50-1.00 titanium, 1.20 1.70 aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003 to 0.008 boron, nickel, and inevitable Impurities Or included in, or consists thereof.

  Still further non-limiting examples of type 718 nickel-base alloys according to the present disclosure include an austenitic matrix including grain boundaries, a near-equilibrium concentration of delta phase precipitates at the grain boundaries, and a total of up to 25 weight percent γ ′ and γ "Including phase precipitates. Alloys in weight percent are 50.0-55.0 nickel, 17-21.0 chromium, up to 0.08 carbon, up to 0.35 manganese, up to 0.35. Silicon, 2.8 to 3.3 molybdenum, greater than 0 to 5.5 niobium and tantalum (total of niobium and tantalum is 4.75 to 5.5), 0.65 to 1.15 It further comprises or consists of titanium, 0.20 to 0.8 aluminum, up to 0.006 boron, iron, and inevitable impurities.

  Aspects of the present disclosure include articles of manufacture made by the methods of the present disclosure and / or including alloys according to the present disclosure. Non-limiting examples of articles of manufacture according to the present disclosure include supersonic or spacecraft TPS faceplates, honeycomb cores, and honeycomb panels.

  The following examples are intended to further illustrate certain non-limiting embodiments without limiting the scope of the invention. Those skilled in the art will appreciate that variations of the following examples are possible within the scope of the invention, which is defined only by the claims.

[Example 1]
The two alloys were heated to 1725 ° F. (940.6 ° C.) and held at that temperature for 3 hours to produce a 0.080 inch (2.03 mm) thick ATI 718Plus® alloy sheet and A 0.4 inch (10.2 mm) diameter alloy 718 rod was heat treated in accordance with a non-limiting embodiment of the present disclosure. Thereafter, the sample was air-cooled.

  For comparison purposes, a sample of the same alloy was heat treated by the following standard γ '/ γ "aging heat treatment.

  A 0.080 inch (2.03 mm) thick sheet of ATI 718Plus® alloy was heated to 1750 ° F. (954.4 ° C.), held at that temperature for 45 minutes, and air cooled. After cooling, the sample was aged at 1450 ° F. (787.8 ° C.) for 8 hours. The sample was cooled to 1300 ° F. (704.4 ° C.) at 100 ° F./hour (55.6 ° C./hour) and held at 1300 ° F. (704.4 ° C.) for 8 hours. After aging, the ATI 718Plus® alloy sample was air cooled.

  In addition, a 0.4 inch (10.2 mm) diameter alloy 718 rod was heated to 1750 ° F. (954.4 ° C.), held at that temperature for 45 minutes, and air cooled. After cooling, the alloy 718 sample was aged at 1325 ° F. (718.3 ° C.) for 8 hours. The sample was cooled to 1150 ° F. (621.1 ° C.) at 100 ° F./hour (55.6 ° C./hour) and held at 1150 ° F. (621.1 ° C.) for 8 hours. After aging, the sample was air-cooled.

[Example 2]
The heat treated sample from Example 1 was exposed to thermal cycling. ATI 718Plus® alloy samples were circulated from ambient temperature to either 1650 ° F. (898.9 °) or 1550 ° F. (843.3 ° C.). An alloy 718 sample was cycled from ambient temperature to 1650 ° F. (898.9 °). FIG. 7 is a schematic depiction of the thermal cycle used, the temperature shown being that of the alloy sample, not the furnace temperature. The top plot, contained in FIG. 7, reflects the slow cooling rate (approximately 10 ° F./min (5.6 ° C./min)) and shows the general behavior of the thick sample. The lower plot reflects the fast cooling rate (about 1500 ° F./min (833 ° C./min)) and shows the general behavior of the thin sample. The cooling rate shown in FIG. 7 is an estimate, but the peak temperature and holding time in FIG. 7 accurately represent what the alloy has received.

[Example 3]
After exposure to thermal cycling, the samples were tensile tested at room temperature according to standard test procedures described in ASTM E8-09 / E8M-09. A sample when heat treated and a plot of ultimate tensile strength after 1 and 5 thermal cycles is provided in FIG. The left plot of FIG. 8 shows the ultimate tensile strength as a function of the number of heat treatment cycles of the ATI 718Plus® alloy sample cooled at the slow cooling rate described in Example 2. The plot on the right side of FIG. 8 shows the ultimate tensile strength as a function of the number of heat treatment cycles of the ATI 718Plus® alloy cooled at the fast cooling rate described in Example 2. The top of the plot of FIG. 8 shows ATI 718 Plus (ATI 718 Plus, heat-treated according to embodiments of the present disclosure as described in Example 1, thermally cycled to a peak sample temperature of 1650 ° F. (898.9 ° C.). (Registered trademark) alloy. The bottom of the plot of FIG. 8 shows ATI 718 Plus (FIG. 8) heat-treated according to embodiments of the present disclosure as described in Example 1, thermally cycled to a peak sample temperature of 1550 ° F. (843.3 ° C.). (Registered trademark) alloy.

  The verification of FIG. 8 shows that the δ phase aging treatment of the present invention can provide a lower initial strength than the conventional γ ′ / γ ”aging treatment, but the variation in ultimate tensile strength during thermal cycling is significantly less. Represents the data of Figure 8, but the y-axis is more prominent in Figure 9 which represents the ratio between the ultimate tensile strength after the sample has undergone thermal cycling and the ultimate tensile strength when heat treated. It is clearly shown that the δ phase heat treatment embodiment according to the present disclosure produced an alloy exhibiting significantly more stable ultimate tensile strength after at least 5 thermal cycles of thermal cycling.

  FIG. 10 includes a plot of the yield strength of the sample included in FIG. The plot of FIG. 10 is in the same orientation as FIG. 8 with respect to cooling rate and peak sample temperature. Considering what is shown in FIG. 10, the δ-phase aging treatment of the present invention may provide a lower initial yield strength than the conventional γ ′ / γ ”aging treatment, but the δ-phase heat treatment during thermal cycling was performed. It can be seen that the variation in the yield strength of the alloy is significantly less, which represents the data in Figure 10, where the y-axis represents the ratio between the yield strength after the sample has undergone thermal cycling and the yield strength when heat treated. Represented more clearly in Figure 11. Figure 11 clearly shows that the δ phase heat treatment embodiment according to the present disclosure produced an alloy exhibiting significantly more stable yield strength after thermal cycling of at least 5 thermal cycles. .

  FIG. 12 includes a plot of the percent elongation of the sample included in FIG. The plot of FIG. 12 is in the same orientation as FIG. 8 with respect to cooling rate and peak sample temperature. Considering what is shown in FIG. 12, the δ phase aging treatment of the present invention may provide a higher elongation than the conventional γ ′ / γ ”aging treatment, but the δ phase heat treated alloy during thermal cycling It can be seen that the variation in the elongation of the sample is remarkably small, which represents the data in Figure 12, where the y-axis represents the ratio between the elongation after the sample is subjected to thermal cycling and the elongation when it is heat treated. Figure 13 clearly shows that the δ phase heat treatment embodiment according to the present disclosure produced an alloy that exhibited significantly more stable elongation after thermal cycling of at least five thermal cycles.

  Samples of alloy 718 when heat treated in Example 1 and thermally cycled to 1650 ° F. (898.9 °) in Example 2 are described in ASTM E8-09 / E8M-09. Tensile tests were performed at room temperature according to standard test procedures. A sample of the heat treated and the ultimate tensile strength plot after 1 and 5 thermal cycles is provided in FIG. The left plot of FIG. 14 shows the ultimate tensile strength as a function of the number of heat treatment cycles of alloy 718 thermally cycled using the slow cooling rate described in Example 2, the right plot It was thermally circulated using the fast cooling rate described in Example 2.

  The verification of FIG. 14 provides an alloy in which the δ phase aging treatment of the present invention exhibits a lower initial strength than the conventional γ ′ / γ ”aging treatment, but also exhibits significantly less variation in ultimate tensile strength when subjected to thermal cycling. This represents the data of Figure 14, but the y-axis represents the ratio between the ultimate tensile strength after the sample has undergone thermal cycling and the ultimate tensile strength when heat treated, and more in FIG. Figure 15 clearly shows that the δ phase heat treatment embodiment according to the present disclosure produced an alloy exhibiting significantly more stable ultimate tensile strength after at least 5 thermal cycles of thermal cycling.

  FIG. 16 includes a plot of the yield strength of the sample included in FIG. The plot of FIG. 16 is in the same orientation as FIG. 14 with respect to cooling rate and peak sample temperature. Considering what is shown in FIG. 16, the δ phase aging treatment of the present invention may provide a lower initial yield strength than the conventional γ ′ / γ ”aging treatment, but the δ phase heat treatment during thermal cycling was performed. It can be seen that the variation in the yield strength of the alloy is remarkably small, which represents the data in Figure 16, where the y-axis shows the ratio between the yield strength after the sample has undergone thermal cycling and the yield strength when heat-treated. It is more pronounced in Fig. 17. Fig. 17 clearly shows that the δ phase heat treatment embodiment according to the present disclosure produced an alloy that exhibited significantly more stable yield strength after thermal cycling of at least 5 thermal cycles. .

  FIG. 18 includes a plot of the percent elongation of the sample included in FIG. The plot of FIG. 18 is in the same orientation as FIG. 14 with respect to cooling rate and peak sample temperature. Considering what is shown in FIG. 18, the δ-phase aging treatment of the present invention may provide a higher elongation than the conventional γ ′ / γ ”aging treatment, but the δ-phase heat-treated alloy during thermal circulation It can be seen that the variation in the elongation of the sample is remarkably small, which represents the data in Figure 18, where the y-axis represents the ratio between the elongation after the sample is subjected to thermal cycling and the elongation when it is heat treated. Figure 19 clearly shows that the δ-phase heat treatment embodiment according to the present disclosure produced an alloy that exhibited significantly more stable elongation after thermal cycling of at least 5 thermal cycles.

[Example 4]
The surface area of the sample tensile tested in Example 3 was verified using a dark field optical microscope. 20A is a photomicrograph of the surface area of a δ-phase heat treated ATI 718Plus® alloy sample described in Example 1. FIG. In FIG. 20A, the thick white plate-like crystals arranged mainly at the grain boundaries are δ-phase plate-like crystals generated by the δ-phase heat treatment according to the non-limiting embodiment of the present disclosure. FIG. 20B is a photomicrograph of the surface area of the same ATI 718Plus® alloy sample after 5 thermal cycles to a peak sample temperature of 1650 ° F. (898.9 °). It may be seen that there is little difference, if any, in the amount of δ phase plate crystals in the sample after 5 thermal cycles to a peak sample temperature of 1650 ° F. (898.9 °). This correlates well with the tensile test of Example 3 showing that the δ-phase heat treated ATI 718Plus® alloy sample described in Example 1 exhibited tensile properties with low variation with respect to thermal cycling. To do.

  20C is a photomicrograph of the surface area of an ATI 718Plus® alloy sample heat treated by the conventional γ ′ / γ ″ heat treatment described in Example 1. As seen in FIG. 20A, the microstructure Is observed to contain a small amount of δ phase intergranular precipitates, which amount is less than that of the sample that has undergone the δ phase heat treatment, however, in Figure 20D, 5 to 1650 ° F (898.9 °). It can be seen that after a number of thermal cycles, the microstructure has clearly changed to include a significant amount of δ phase at the grain boundaries, and this change in the microstructure caused by thermal cycling is the γ ′ shown in Example 3. / Γ "heat treatment and reflected in the degradation of the tensile properties of the thermally circulated nickel base superalloy sample.

  21A is a photomicrograph of the surface area of a δ-phase heat treated ATI 718Plus® alloy sample described in Example 1. FIG. The thick white plate crystals mainly on the grain boundaries are the δ phase plate crystals produced by the δ phase heat treatment according to a non-limiting embodiment of the present disclosure. FIG. 21B is a photomicrograph of the surface area of the same sample after 5 thermal cycles to a peak sample temperature of 1550 ° F. (843.3 ° C.). It may be observed that there is little difference, if any, in the amount of δ phase plate crystals after 5 thermal cycles to a peak sample temperature of 1550 ° F. (843.3 ° C.). This correlates well with the tensile test of Example 3 showing that the δ-phase heat treated ATI 718Plus® alloy sample described in Example 1 exhibited tensile properties with low variation with respect to thermal cycling. To do.

  21C is a photomicrograph of the surface area of an ATI 718Plus® alloy sample heat treated by the conventional γ ′ / γ ”heat treatment described in Example 1. As seen in FIG. 21A, the microstructure May contain a small amount of δ phase intergranular precipitates, which is observed to be less than the samples that have undergone the δ phase heat treatment, however, in Figure 21D, to 1550 ° F (843.3 ° C). After 5 thermal cycles, it can be seen that the microstructure has clearly changed to include a significant amount of δ phase at the grain boundaries, and this change in the microstructure caused by thermal cycling is the γ shown in Example 3. This is reflected in the deterioration of the tensile properties of the '/ γ' heat treated and thermally circulated nickel base superalloy sample.

  22A is a photomicrograph of the surface area of the 718-phase heat treated alloy 718 sample described in Example 1. FIG. The thick white plate crystals mainly on the grain boundaries are the δ phase plate crystals produced by the δ phase heat treatment according to a non-limiting embodiment of the present disclosure. FIG. 22B is a photomicrograph of the surface area of the same sample after five thermal cycles to a peak sample temperature of 1650 ° F. (898.9 °). It is observed that there is little difference, if any, in the amount of δ phase plate crystals after 5 thermal cycles to a peak sample temperature of 1650 ° F. (898.9 °). This correlates well with the tensile test of Example 3 which shows that the 718 phase heat treated alloy 718 sample described in Example 1 exhibited tensile properties with low variation with respect to thermal cycling.

  22C is a photomicrograph of the surface area of an alloy 718 sample heat treated by the conventional γ ′ / γ ″ heat treatment described in Example 1. As seen in FIG. 22A, the microstructure is a small amount of δ phase. It can be observed that the grain boundary precipitates may be present in an amount that is less than that of the sample that had undergone the δ phase heat treatment, however, in Figure 22D, five thermal cycles to 1650 ° F (898.9 °). Later, it can be seen that the microstructure has clearly changed to include a significant amount of δ phase at the grain boundaries. This change in the microstructure caused by thermal cycling is due to the γ ′ / γ ″ heat treatment shown in Example 3. And reflected in the deterioration of the tensile properties of the thermally circulated nickel-base superalloy.

  The present disclosure has been described with reference to various examples, illustrations, and non-limiting embodiments. Those skilled in the art can make various substitutions, modifications, or combinations of any of the disclosed embodiments (or portions thereof) without departing from the scope of the invention, which is defined only by the claims. Recognize Accordingly, the present disclosure is assumed and understood to include additional embodiments not explicitly described herein. The present disclosure is not limited by the various examples, illustrations, and descriptions of non-limiting embodiments, but only by the claims. Thus, it is understood that the claims may be modified to add features to the claimed invention as variously described herein while filing this patent application.

Claims (26)

A method of heat-treating a nickel-base alloy,
Heating the 718 nickel-base alloy to a heat treatment temperature within a heat treatment temperature range;
During a heat treatment time sufficient to form an equilibrium concentration or near equilibrium concentration of δ phase precipitates at grain boundaries of the alloy, and a total of up to 25 weight percent γ ′ and γ ″ phases within the alloy. Holding the alloy within a heat treatment temperature range, and cooling the nickel-based alloy.   The heat treatment temperature range is in the range of a temperature 20 ° F (11 ° C) higher than the nose of the TTT diagram of the δ phase precipitate to a temperature 100 ° F (55.6 ° C) lower than the nose of the TTT diagram. The method according to 1.   The method of claim 1, wherein the heat treatment time is in the range of 30 minutes to 300 minutes.   The method of claim 1, wherein cooling the nickel-based alloy comprises air cooling.   The method of claim 1, wherein cooling the nickel-based alloy comprises cooling the alloy at a cooling rate that does not exceed about 1 ° F. per minute (0.56 ° C. per minute).   The method of claim 1, wherein the 718-type nickel-base alloy includes nickel, chromium, and iron, is strengthened by niobium, and optionally includes one or more alloying elements of aluminum and titanium.   The 718-type nickel base alloy is, by weight percent, up to 0.1 carbon, 12-20 chromium, up to 4 molybdenum, up to 6 tungsten, 5-12 cobalt, 6-14 iron, 4-8 Niobium, 0.6-2.6 aluminum, 0.4-1.4 titanium, 0.003-0.03 phosphorus, 0.003-0.015 boron, nickel, and inevitable impurities The sum of the weight percent of molybdenum and the weight percent of tungsten is at least 2 and does not exceed 8, the sum of the atomic percent of aluminum and the atomic percent of titanium is 2-6, and the atomic percent of aluminum And the atomic percent of titanium is at least 1.5 and the sum of the atomic percent of aluminum and the atomic percent of titanium is the niobium Divided by atomic percent, it is 0.8 to 1.3 The method of claim 1.   The 718-type nickel-base alloy is, by weight percent, 0 to about 0.08 carbon, 0 to about 0.35 manganese, about 0.003 to about 0.03 phosphorous acid, 0 to about 0.015. Sulfur, 0 to about 0.35 silicon, about 17 to about 21 chromium, about 50 to about 55 nickel, about 2.8 to about 3.3 molybdenum, about 4.7 percent to about 5.5. Of niobium, 0 to about 1 cobalt, about 0.003 to about 0.015 boron, 0 to about 0.3 copper, 12 to 20 iron, aluminum, titanium, and unavoidable impurities The sum of the percent and the atomic percent of titanium is about 2 to about 6 percent, the ratio of the atomic percent of aluminum to the atomic percent of titanium is at least about 1.5, and the atomic percent of aluminum + titanium of Which the serial sum divided by atomic percent niobium is equal to about 0.8 to about 1.3 The method of claim 1.   The 718-type nickel-base alloy is, by weight percent, 0.01-0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004-0.020 phosphorus, up to 0.025. Of sulfur, 17.00 to 21.00 chromium, 2.50 to 3.10 molybdenum, 5.20 to 5.80 niobium, 0.50 to 1.00 titanium, 1.20 to 1.70 Aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003 to 0.008 boron, nickel, and inevitable impurities The method of claim 1.   The 718-type nickel-base alloy is 50.0-55.0 nickel, 17-21.0 chromium, up to 0.08 carbon, up to 0.35 manganese, up to 0.35 silicon by weight percent. 2.8 to 3.3 molybdenum, greater than 0 to 5.5 niobium and tantalum (total of niobium and tantalum is 4.75 to 5.5), 0.65 to 1.15 titanium, The method of claim 1 comprising 0.20 to 0.8 aluminum, up to 0.006 boron, iron, and inevitable impurities.   The method of claim 1, wherein the 718-type nickel-base alloy comprises at least one of a foil, a honeycomb core, and a honeycomb panel. Further comprising stabilizing the heat treatment of the alloy after cooling of the alloy;
Stabilizing the heat treatment
Heating the 718-type nickel-based alloy to a heat treatment stabilization temperature of 1700 ° F. (926.7 ° C.) or less, wherein the heat treatment temperature is equal to a predicted maximum practical temperature of an article comprising the alloy; and The method of claim 1, comprising cooling the alloy from the heat treatment stabilization temperature.   The method of claim 12, wherein cooling the alloy from the heat treatment stabilization temperature comprises air cooling.   The method of claim 12, wherein cooling the alloy from the heat treatment stabilization temperature comprises cooling at a cooling rate not exceeding about 1 ° F. per minute (0.56 ° C. per minute). A method of heat-treating a nickel-base alloy,
Heating the nickel-based alloy to a heat treatment temperature in the range of 1700 ° F. (926.7 ° C.) to 1725 ° F. (940.6 ° C.);
Holding the alloy at the heat treatment temperature for a heat treatment time within a range of 30 minutes to 300 minutes, and air cooling the nickel-base alloy,
The alloy is, by weight, 17.00-21.00 chromium, 2.50-3.10 molybdenum, 5.20-5.80 niobium, 0.50-1.00 titanium, 1. 20 to 1.70 aluminum, 8.00 to 10.00 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003 to 0.008 boron, The method comprising: 01-0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004-0.020 phosphorus, up to 0.025 sulfur, nickel, and inevitable impurities. Further comprising stabilizing a heat treatment of the nickel-based alloy after cooling the nickel-based alloy;
Stabilizing the heat treatment
Heating the nickel-based alloy to a heat treatment stabilization temperature that is a predicted maximum practical temperature of an article comprising the nickel-based alloy and not greater than about 1700 ° F. (926.7 ° C.); and 16. The method of claim 15, comprising air cooling.   The method of claim 15, wherein the nickel-based alloy comprises at least one of a foil, a honeycomb core, and a honeycomb panel. 718 type nickel base alloy,
An austenite matrix including grain boundaries;
Δ phase precipitates at or near equilibrium at the grain boundaries;
A total of up to 25 weight percent of γ ′ and γ ″ phase precipitates,
The 718-type nickel-base alloy, wherein the 718-type nickel-base alloy includes nickel, chromium, and iron, is strengthened by niobium, and includes one or more alloying elements of any aluminum and titanium. In weight percent, up to 0.1 carbon, 12-20 chromium, up to 4 molybdenum, up to 6 tungsten, 5-12 cobalt, 6 up to 14 iron, 4-8 niobium, 0.6- 2.6 aluminum, 0.4-1.4 titanium, 0.003-0.03 phosphorus, 0.003-0.015 boron, nickel, and inevitable impurities,
The sum of the weight percent of molybdenum and the weight percent of tungsten is at least 2 and does not exceed 8;
The sum of atomic percent of aluminum and atomic percent of titanium is 2-6,
The ratio of atomic percent of aluminum to atomic percent of titanium is at least 1.5;
The 718-type nickel-base alloy of claim 18, wherein the sum of the atomic percent of aluminum and the atomic percent of titanium divided by the atomic percent of niobium is 0.8 to 1.3.   In weight percent, 0 to about 0.08 carbon, 0 to about 0.35 manganese, about 0.003 to about 0.03 phosphorous acid, 0 to about 0.015 sulfur, 0 to about 0.0. 35 silicon, about 17 to about 21 chromium, about 50 to about 55 nickel, about 2.8 up to about 3.3 molybdenum, about 4.7 percent to about 5.5 niobium, 0 to about 1 Cobalt, about 0.003 to about 0.015 boron, 0 to about 0.3 copper, 12 to 20 iron, aluminum, titanium, and unavoidable impurities, including atomic percent of aluminum and atomic percent of titanium The sum of atomic percent of aluminum and atomic percent of titanium is at least about 1.5 and the sum of atomic percent of aluminum + titanium is the niobium atom. Par Divided by cement is equal to about 0.8 to about 1.3, 718-type nickel-base alloy according to claim 18.   0.01 to 0.05 carbon, up to 0.35 manganese, up to 0.035 silicon, 0.004 to 0.020 phosphorus, up to 0.025 sulfur, 17.00 to 21 by weight percent 0.000 chromium, 2.50-3.10 molybdenum, 5.20-5.80 niobium, 0.50-1.00 titanium, 1.20-1.70 aluminum, 8.00-10 718 of claim 18 comprising 0.000 cobalt, 8.00 to 10.00 iron, 0.008 to 1.40 tungsten, 0.003 to 0.008 boron, nickel, and inevitable impurities. Type nickel base alloy.   In weight percent, 50.0-55.0 nickel, 17-21.0 chromium, up to 0.08 carbon, up to 0.35 manganese, up to 0.35 silicon, 2.8-3.3. Molybdenum, greater than 0 to 5.5 niobium and tantalum (total of niobium and tantalum is 4.75 to 5.5), 0.65 to 1.15 titanium, 0.20 to 0.8 19. The 718 nickel-base alloy of claim 18 comprising aluminum, up to 0.006 boron, iron, and inevitable impurities.   An article of manufacture made by a process comprising the method of claim 1.   24. The article of manufacture of claim 23, wherein the article of manufacture comprises at least one of a supersonic vehicle or spacecraft thermal protection system faceplate, honeycomb core, and honeycomb panel.   An article of manufacture comprising the alloy of claim 12.   26. The article of manufacture of claim 25, wherein the article of manufacture comprises one of a thermal protection system faceplate for a supersonic aircraft, a honeycomb core, and a honeycomb panel.