waspaloy
a modified waspaloy composition for such shafts and disks is described in us 5 120 373 .
waspaloy - nickel alloy precipitation hardened by gamma prime with high strength and oxidation resistance to 1600°f. applications are gas turbine components including shafts and fasteners .
waspaloy is a precipitation hardening, nickel - based alloy which has been used in elevated temperature applications. the alloy has been used for gas turbine engine parts which require considerable strength and corrosion resistance at temperatures up to 1600°f (871°c). waspaloy is usually vacuum - induction plus consumable electrode remelted .
waspaloy has excellent resistance to corrosion by combustion products, encountered in gas turbines and aircraft jet engines, at temperatures up to 1600°f. intergranular oxidation occurs at temperatures above 1600°f .
an as - cast - and - wrought embodiment of the present invention has been reduced to practice and comparatively evaluated with alloy 718 and waspaloy, the closest competitive alloys. as discussed earlier, alloy 718 has excellent castability and weldability, but insufficient mechanical properties above about 1150°f. waspaloy has good mechanical properties up to about 1300°f, but is castable and weldable only with difficulty .
the preferred composition can be viewed as a derivative of the commercial alloy known as waspaloy (nominal composition 19. 5% cr, 13. 5% co, 4. 2% mo, 3. 0% ti, 1. 4% al, 0. 05% c, 0. 007% b, 0. 07% zr, 0 - 2% fe, balance ni). waspaloy is the most widely used superalloy and it is a significant economic advantage that the present invention preferred composition can be produced using a large quantity of waspaloy scrap or revert material .
this page has links to all data sheets in matweb for the tradename waspaloy. we have several search tools, listed above, that give you more efficient methods to reach the information that you need .
waspaloy® ams 5706 bar is difficult to machine, even in the solution treated condition. rigid set - up, plenty of power, sharp tools and positive cuts are important. use of carbide or ceramic tools is required .
in casting and weldability trials, the wrought alloy 991 and the alloy 718 had excellent castability and weldability, evaluated qualitatively. the waspaloy baseline alloy was difficult to cast and weld, and showed extensive surface cracking during casting .
waspaloy® round bar - ams 5708 (type 2 is capable of ams 5709) is a nickel - based alloy containing chromium and cobalt typically used in aircraft fasteners where high strength up to 1500° f and oxidation resistance up to 1750° f is required. waspaloy® round bar is multiple melted, usually with either a vacuum induction melt (vim) followed by a vacuum arc remelt (var), or a vacuum induction melt (vim) followed by an electroslag remelt (esr) .
waspaloy is an austenitic super alloy that is based in nickel. it is age - hardening and was created by the united technologies corp. this alloy is often used in severe conditions for shafts, rings, seals, turbine disks, and gas turbine blades .
non - magnetic. waspaloy® bar - ams 5706 maintains high strength, toughness, and excellent rupture properties to 1400ºf (760˚c). this alloy has good resistance to oxidation and sulfidation to 1600ºf (871˚c) due to its high chromium content. waspaloy® bar - ams 5706 displays excellent resistance to corrosion by combustion products encountered in gas turbines and aircraft jet engines at temperatures up to 1600ºf (871ºc). intergranular oxidation occurs at temperatures above 1600ºf (871ºc). this alloy has excellent resistance to stress corrosion cracking and adequate hot corrosion resistance .
another advantage is that this material in astm 10 and finer grain size can be electron beam welded without difficulty. in contrast, conventional (coarse grain) waspaloy is marginally e. b. weldable at best, even though it contains less gamma prime and is weaker .
abdul - latif aa, ferney vv, saanouni kk. fatigue damage initiation in waspaloy under complex cyclic loading. asme. j. eng. mater. technol. 1999; 121 (3): 278 - 285. doi: 10. 1115 / 1. 2812376 .
related compositions are known in the art including those superalloy materials known as waspaloy, udimet 720, astroloy and rene 88 which are described in patents including u. s. pat. nos. 2, 977, 222, 4, 083, 734, and 4, 957, 567 .
the major difference between waspaloy and the preferred composition is that the preferred composition contains larger amounts of gamma prime formers (al and ti) and therefore contains about 1. 3 times more gamma prime (about 40% by volume) than does waspaloy. the increased gamma prime levels produce increased strength properties. the material also has an increased gamma prime solvus temperature, this permits the material to be processed below the gamma prime solvus, but at a high enough temperature so that the capacities of forging equipment is not exceeded. the preferred material possesses, to our knowledge, the best resistance to crack growth for this level of gamma prime and strength .
the alloys were tested in creep at 1200°f and 98, 000 pounds per square inch load. the accepted measure of performance is the time to creep to 0. 2 percent strain, with longer times being better. the alloy 718 had creep times ranging from 40 to 105 hours. the alloy 991 had creep times ranging from 155 to more than 210 hours (testing was terminated at 210 hours). the waspaloy had creep times ranging from 155 to more than 215 hours (testing was terminated at 215 hours). the alloy 718 is not suitable for service at this temperature, while the alloy 991 had properties comparable with those of waspaloy .
abstract of the disclosure weldable cast nickel base superalloy nickel base superalloys of the type referred to as waspaloy are rendered weldable by limiting the iron content to about one twentieth of that which is commonly present, adding small amounts of manganese to the alloy and removing the zirconium which is commonly present. in addition, the sulfur, bismuth and lead levels are held to the lowest possible limits, and preferably the aluminum and molybdenum are maintained in the lower half of their normal range. by implementing these alloying strategies, the weldability of the cast material is dramatically improved and for the first time castings of the waspaloy materials are rendered consistently weldable on a commercial scale .
the low - cycle fatigue damage initiation in waspaloy under complex cyclic loading (out - of - phase) is studied from experimental and theoretical viewpoints. special emphasis is put on the transgranular damage development and results are compared to those reproduced in the literature. a physico - phenomenological model based on slip theory is used to predict the damage initiation lives as well as the directional aspect of the damage distribution. in this model, the micro - damage is supposed to initiate and then evolve on the activated crystallographic slip systems. the theoretical results are compared to both the experimental ones concerning the same material (waspaloy) as well as other experimental results extracted from the literature .
alternatively, an alloy of desired composition may be conventionally processed to have a coarser grain structure, for example, of approximately astm 3 - 7 such as that employed for the commercial alloy known as waspaloy (nominal composition, in weight percent, of 19. 5cr, 13. 5co, 4. 2mo, 3. 0ti, 1. 4al, 0. 05c, 0. 007b, 0. 05 zr, bal ni) .
hardness of aerodyne alloys stock is typically 230 bhn. supplied in the solution treated condition – 1825 - 1900ºf (996 - 1038˚c) for 1 hour. waspaloy® bar - ams 5706 exhibits best machinability in this condition. after machining, parts are normally stabilized at 1550ºf (843˚c) for 4 hours, air cooled, followed by precipitation aging at 1400ºf (760˚c) for 16 hours, air cooled. the hardness of this alloy in the fully heat treated condition ranges from 34 to 44 rockwell c .
annealing hardening and strength properties are developed by precipitation of gamma prime (ni 3 tial). the solution temperature for gamma prime in waspaloy is normally 1860 / 1880°f. this is also the temperature range at which grain growth begins. annealed, or low hardness can be obtained only by cooling very rapidly from temperatures above the gamma prime solvus. water quenching will result in hardnesses as low as rockwell b 90, while air cooling will result in rockwell c 28 / 30. uniform low hardness cannot be obtained on sections having condiderable mass. air cooling is desirable for large sections .
the waspaloy baseline material had a nominal composition, in weight percent, of about 19. 02 percent chromium, about 13. 13 percent cobalt, about 0. 55 percent iron, about 4. 18 percent molybdenum, about 0. 01 percent niobium, about 0. 02 percent tantalum, less than about 0. 01 percent tungsten, less than about 0. 01 percent copper, about 0. 01 percent manganese, about 0. 01 percent vanadium, less than about 0. 01 percent silicon, about 2. 98 percent titanium, about 1. 41 percent aluminum, about 0. 03 percent carbon, less than about 0. 06 percent zirconium, balance nickel and impurities .
waspaloy is one of the original nickel based superalloys. this material uses precipitation hardening forming two phases within one grain of material. the ni, ti and al form the basis of the γ and γ’ phases which make it a superalloy. to stop this material from corroding, we add cr to help out the al. although this material uses precipitates to prevent movement of holes / dislocations in the material, it also uses solid solution strengthening. by adding cr, co and mo, this introduces atomic arrangements and bonds that also make it difficult for dislocations / holes to form, join together and move about. this material is capable of handling temperatures up to 650°c when the part is rotating at high speeds .
welding waspaloy should always be in the annealed or solution treated condition before attempting welding. good fit up and careful control of arc length and current input will minimize weld restraint. a clean surface is important - - chemical descaling, cleaning solvents, vapor blasting (not sand blasting), and emery cleaning are recommended. any molten weld metal should be protected from atmospheric contamination. argon is recommended for both sides of butt joints. rapid cooling of the weld area is best practice. copper back - up bars and / or water - cooled fixtures or sprays are recommended. all welded parts should be re - solution treated .
strain - age
cracking can be minimized by heating welded parts through the aging temperature as rapidly as possible .
this is another precipitation hardened nickel based superalloy. when we compare it to waspaloy we see it has more ti and al, meaning it is lighter. it also means we can form more γ’ phase which makes the material less sensitive to changes in temperature. the cr and al once again provide corrosion resistance. solid solution strengthening is also achieved by adding cr, co and mo. inconel 100 also can have 0. 18% c. this carbon with the help of cr and mo form carbides which is different phase, that sits on the grain boundaries. by having these carbides on the grain boundaries it can also thwart holes / dislocations from causing damage. this is how this material is capable of dealing with temperatures just over 1000°c .
figure 1 is a sectional view of a cast article of manufacture, illustrated as a static structure 20 in the high - pressure turbine of a gas turbine engine. the use of the present invention is not limited to this cast article of manufacture, which is presented by way of illustration and not limitation. the static structure 20 is a relatively thin - walled cast article. the static structure 20 experiences a maximum service temperature of about 1300°f, which is too high a temperature to use alloy 718 as its material of construction. under conventional practice the static structure 20 would be cast of a higher - temperature alloy such as waspaloy or rene™ 220c. however, these latter higher - temperature alloys are difficult and expensive to cast and weld, leading to excessive cost for the static structure 20 .
3, 625, 678; 3, 723, 107; 3, 850, 624; 4, 110, 110; 4, 213, 026 and 4, 456, 481. 128 ~; 9 ~ in view of the substantial number of issued u. s. patents in this limited alloy area, it is not surprising that many elements have been added to and / or removed from the basic composition to achieve various purposes. in particular, u. s. patent no. 3, 166, 412 deals with a casting made from a waspaloy type composition and states, in part, that iron is an undesirable element in the alloy and it should not be present in amounts exceeding 0. 5% and preferably not greater than 0. 25% the nature of the problems resulting from the presence of iron and / or the benefits achieved by limiting iron to these ranges is not set forth. the patent makes no reference to welding or weldability. similarly, certain patents teach the addition of manganese in superalloys for purposes relating to improving weldability, for example, u. s. patent no .
the thermodynamic stability of the alloys at the required service temperatures is an important consideration. to evaluate the thermodynamic stability, specimens were subjected to creep loading at 1200°f for 212 hours at a loading of 98, 000 pounds per square inch, and thereafter exposed to a temperature of 1400°f for 100 hours. the specimens were thereafter tensile tested at 1300°f. comparison specimens were not subjected to the creep testing and exposure at 1400°f, but were tensile tested at 1300°f. in each case, the uts ratio is the ratio of the ultimate tensile strength of the exposed specimens to the ultimate tensile strength of the unexposed specimens. the ys ratio is the ratio of the 0. 2 percent yield strength of the exposed specimens to the 0. 2 percent yield strength of the unexposed specimens. a ratio of close to 1 is desirable in each case. for the alloy 718, the uts ratio is about 0. 8, and the ys ratio is about 0. 66. for the alloy 991, the uts ratio is about 0. 91, and the ys ratio is about 0. 87. for the waspalloy, the uts ratio is about 1. 05, and the ys ratio is about 1. 04. alloy 718 has significant degradation of properties in this test, alloy 991 has moderate but acceptable degradation of properties, and waspaloy actually has an improvement in properties .
ra330® - the workhorse of austenitic heat resistant alloys. good strength, carburization and oxidation resistance up to 2100°f .
ra333® - a nickel base superalloy with excellent carburization, oxidation, and hot corrosion resistance. it has high creep rupture strength with exceptional ability to withstand repeated thermal shock ...
ra 602 ca® - one of the most oxidation resistant high strength, heat resistant nickel alloys available. useful through 2200°f .
inconel 600 - a nickel - chromium alloy with good carburization and oxidation resistance through 2000°f .
601 is a nickel - base alloy with high chromium and an aluminum addition. outstanding oxidation resistance to 2200°f, good strength and carburization resistance .
625 alloy is high creep - rupture strength, oxidation resistant to 1800°f (982°c). excellent resistance to hot seawater, scrubber environments and reducing acids .
inconel 718 - nickel alloy precipitation hardened by gamma prime and double prime. readily fabricated, weldable even in the hardened condition. used for gas turbine components to 1200°f, as well as ...
alloy x - good strength and ease of fabrication, with excellent oxidation resistance through 2000°f. widely used for aircraft, marine and industrial gas turbine combustors .
invar 36 is a nickel - iron, low - expansion alloy containing 36% nickel. used for molds and dies to form composites .
al - 6xn® alloy (uns n08367) is a low carbon, high purity, nitrogen - bearing
super - austenitic
stainless alloy. the al6xn alloy was designed to be a seawater resistant material and has since been demonstrated ...
alloy x - 750 is a nickel chromium alloy similar to alloy 600 but made precipitation hardenable by additions of aluminum and titanium .
800 h / at - high strength austenitic heat resistant alloy for asme code applications to 1650°f .
alloy 20 - the alloy designated specifically to withstand sulfuric acid. practical immunity to chloride stress corrosion cracking. stabilized to prevent intergranular corrosion as welded. resistant to ...
zeron 100 - a highly alloyed super duplex stainless steel for use in seawater desalination and many aggressive environments. minimum pren of 40 .
ldx 2101 - a lean duplex stainless steel offering excellent strength, scc resistance and economy .
ra 253 ma® - an advanced micro - alloyed austenitic heat resistant alloy. high creep - rupture strength and outstanding oxidation resistance through 2000°f .
309 stainless steel - austenitic, oxidation resistant to 1900°f, moderate strength. useful in reducing sulfidizing atmospheres .
310 stainless steel - austenitic heat resistant grade with higher chromium and nickel for oxidation resistance beyond 2000°f. good sulfidation and hot corrosion resistance .
stainless 440c is a high - carbon martensitic stainless steel. as a martensitic stainless steel, 440c is magnetic and can be hardened by heat treatment .
321 stainless steel - a titanium stabilized austenitic stainless commonly used for service in the 1000 - 1600°f range .
17 - 4 is an age - hardening martensitic stainless steel. good strength and corrosion resistance. simple heat treatment .
a286 - precipitation hardenable iron base alloy for continuous use from - 320 to 1000°f. aqueous corrosion resistance similar to 316l stainless. used for jet engine components, high temperature fasteners ...
304h is an 18 - 8 stainless with elevated carbon and coarser grain structure to increase high temperature strength. useful up to 1500°f .
304 / 304l is an austenitic stainless steel; low carbon for as - welded corrosion resistance .
316 / l, 316 stainless steel - molybdenum alloyed austenitic stainless. most popular chemical process grade .
416 stainless steel is a free - machining martensitic stainless steel with 12 - 13% chromium that can be hardened by heat treatment to higher strength and hardness levels. in the annealed condition, it has ...
446 stainless steel is a high chromium ferritic alloy with excellent oxidation and sulfidation resistance. low strength .
317l / 317 stainless steel - an austenitic stainless steel with increased molybdenum content for improved pitting resistance .
303 is an
18 - 8
chromium - nickel stainless steel modified by the addition of selenium or sulphur, as well as phosphorus, to improve machinability and non - seizing properties. .
prodec® 303 - rolled alloys machining grade of 303 stainless steel is a fully resulfurized free - machining austenitic stainless steel melted and processed to maximize machinability. .
prodec® 304l - rolled alloys machining grade of 304 / l stainless steel for improved machinability and outstanding uniformity. .
prodec® 316 / 316l - rolled alloys machining grade of 316 / l stainless steel for improved machinability and outstanding uniformity. .
prodec® 17 - 4 is an enhanced machining version of 17 - 4 stainless ph. trials have shown prodec 17 - 4 to provide up to 30% faster machining speeds without sacrificing tool life when compared to standard ...
rolled alloys offers 13 - 8 round bar in stock and available online. martensitic ph stainless with high strength, hardness, superior toughness and good corrosion resistance .
nitronic® 50 / n50 - high strength and good corrosion resistance. nearly 2x strength of 304 & 316 with better corrosion resistance than 317l .
nitronic® 60 / n60 - excellent galling resistance at high temperatures. used for fasteners and pins .
6 - 4 titanium - most widely used of all of the alpha - beta titanium alloys. used through 750°f .
6al - 4v eli - extra low interstitial version of 6 - 4 grade to maximize toughness. commonly used for medical implants .
ti 6al - 4v sta (solution treated and aged) is a modified version of ti 6al - 4v. it is heat treated for high strength in sections under 4
thick .
188 - cobalt base with high strength and oxidation resistance to 2000°f, used for gas turbine combustor cans .
alloy c263 is an aluminum - titanium age hardening nickel base superalloy welding wire. gas tungsten arc welding is normally carried out using argon shielding gas .
rené 41 - precipitation hardened nickel alloy with excellent strength through 1600°f. used for gas turbine and missile hot components, including bolting and springs .
tribaloy® t - 800® is a cobalt - chromium - molybdenum alloy which inhibits galling between sliding surfaces where lubrication is difficult. anti - galling hardfacing weld wire. low coefficient of friction .
694 (cm - 64) - hardfacing weld wire for turbine blade interlock surfaces. resists wear, thermal fatigue and oxidation .
alloy l605 (also referenced as haynes® 25) is the strongest of the fabricable cobalt alloys, useful for continuous service to 1800°f .
predominantly produced by vim - var melt method. solution treated, centerless ground or rough turned .
the technical data provided is for information only and not for design purposes. it is not warranted or guaranteed .
typical stock removal rate: 30 - 50 surface feet / minute with carbide tooling .
specific gravity... ...... ...... ...... ...... ...... .... 8. 25 density lb / cubic in... ...... ...... ...... ...... ...... ...... ... 0. 294 kg / cubic meter... ...... ...... ...... ...... ...... .. 8138
solution treated 4 hrs. 1975°f (1080°c), ac stabilization aged 24 hrs. 1550°f (843°c), ac precipitation aged 16 hrs. 1400°f (760°c), ac
hot working hot working is usually conducted in the temperature range 1850 / 2150°f. the recommended furnace temperature is 2150°f. finishing should be discontinued at a temperature not lower than 1850°f (optical). whether possible, the hot working should proceed at a rate designed to maintain the proper hot - working temperature through internal
frictional heat .
if deformation is too rapid, the temperature of the workpiece can
build up
and exceed the recommended 2150°f temperature and
hot short
tears will result. the alloy is normally air cooled from the hot - work operation .
* aging: 1550°f (843°c) / 4 hours / a. c. + 1400 (760°c) / 16 hrs / a. c .
* aging: 1550°f (843°c) / 4 hours / a. c + 1400 (760°c) / 16 hrs / a. c .
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this age hardenable nickel base super alloy has very good strength in temperatures up to about 980 o c (1800 o f). it’s strength is generally comparable to that of rene 41 and is generally superior to that of alloy 718 at temperatures exceeding 650 – 705 o c (1200 – 1300 o f) .
the above tensile strength ranges are typical. if you require different please ask .
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the invention relates to nickel base superalloy articles having machined surfaces. the superalloy articles possess superior low cycle fatigue strength and are particularly suited for gas turbine engine components such as shafts, disks, spacers and seals .
nickel base superalloys are commonly employed for gas turbine engine components such as shafts and disks. as a result of the demand for improved performance and efficiency, the components of a modem gas turbine engine operate near the limit of their properties with respect to temperature, stress, and oxidation / corrosion. due to these aggressive operating environments, the superalloy materials from which the components are made must possess a combination of exceptional properties including high strength capability at elevated temperatures and rotational speeds .
in particular, nickel base superalloy articles suitable for components such as shafts and disks must possess superior low cycle fatigue strength because repeated cycling between full engine power and idle induces a cycle of thermomechanical stress within the engine. such superalloy articles must possess superior low cycle fatigue strength in order to withstand such conditions .
superalloy articles for components such as disks are typically machined to bring them to finished geometry. for example, billet material or a forged component may be inserted into a lathe wherein a tool insert removes layers of superalloy material, while the component spins, until the correct geometry or diameter is achieved .
a problem, however, with some prior art machined disks, particularly lathe turned disks using tungsten carbide tool inserts, is that they display low cycle fatigue failures at relatively low lives, under testing conditions .
accordingly, there exists a need for machined nickel base superalloy articles having superior low cycle fatigue strength .
it is also know from q. huang and jing xin ren :
surface integrity and its effects on the fatigue life of nickel based superalloy gtt 33a
, internat. journal fatigue, july 1991, pages 322 to 3. that machining surface irregularities have an effect on low cycle fatigue strength .
it has been found that the low cycle fatigue strength of tungsten carbide turned nickel base superalloy materials suitable for components such as disks (i. e. cast / wrought superalloys) is limited by microstructural damage to the surface and near surface of the superalloy article which occurs during the machining process. for example, during the lathe turning process, the carbide tool insert damages the primary mc carbides thereby resulting in microstructural and residual stress damage to the surface and near surface of the article. testing has shown that this microstructural damage is responsible for initiating low cycle fatigue failures at relatively low lives .
mc carbides typically form in the melt when the material is between its solidus and liquidus temperature range. the m stands for one or more types of metal atoms, including but not limited to, titanium and molybdenum; c represents the carbon present in the carbide. the presence of refractory elements such as molybdenum and titanium in combination with carbon lead to the natural occurrence of mc carbides in cast / wrought superalloys. due to the high temperature of mc carbide formation, these carbides cannot be eliminated or modified through heat treatment practices. a characteristic of the mc carbides is their tendency to be present in linear arrays of individual carbide particles known as carbide stringers after forging. carbide stringers act to increase the effective size of the individual particles which in turn has a negative impact on low cycle fatigue life properties .
in accordance with the invention, a machined surface of a hot deformed nickel base superalloy article possessing an exceptional combination of properties, particularly low cycle fatigue strength is disclosed. the composition of the nickel base superalloy article is, in weight percent, 2. 2al, 4. 6ti, 15. 5cr, 3. 0mo, 13. 5co, 0. 015c, 0. 015b, 0. 04zr, 0. 001 - 0. 005mg, balance ni and unavoidable impurities. the nickel base superalloy further comprises a plurality of discrete mc carbides where m is predominantly titanium and c is carbon, free from. molybdenum for increased fatigue strength. the superalloy is also free of carbide stringers. the machined surface of the nickel base superalloy article is further characterized by the presence of minimal damage during conventional tungsten carbide lathe turning .
providing a nickel base superalloy composition, said composition comprising, in weight percent, 2. 2al, 4. 6ti, 15. 5cr, 13. 5co, 0. 015c, 0. 015b, 0. 04zr, 0. 001 - 0. 005mg, balance ni and unavoidable impurities ;
adding, in weight percent, 3. 0mo, thereby forming a final composition ;
machining the surface of the article, said article being characterised by being free of carbide stringers and by the presence of a plurality of discrete mc carbides, where m is predominantly titanium and c is carbon, which are free from molybdenum for increased fatigue strength .
the subject invention is based in part on the following findings and observations: eliminating molybdenum from the carbides of the above superalloy results in significant improvements in low cycle fatigue life because during machining of the superalloy article, particularly during tungsten carbide lathe turning, such molybdenum - free carbides are not excessively damaged and do not cause premature low cycle fatigue failure of the article. molybdenum' s adverse effect on low cycle fatigue strength based on its presence in carbides of wrought superalloys has never before been known or appreciated. this is a significant finding
an advantage of the invention is that superalloy articles made therefrom possess excellent low cycle fatigue strength .
yet another advantage of the invention is that ingots made from the superalloy material of the invention can be fabricated in various size diameters such as diameters greater than or equal to 24 inches (0. 61m) thus allowing for the production of large size gas turbine engine hardware such as disks. this is a significant advantage because ingots fabricated from some prior art wrought superalloy materials have a maximum diameter of 20 inches (0. 51m) before casting defects occur and thus they cannot be employed for production of large size gas turbine engine hardware .
figure 1 is a weibull chart depicting the low cycle fatigue strength of the present invention compared to the low cycle fatigue strength of a prior art alloy .
in accordance with the invention, a nickel base superalloy article is disclosed. the article possesses an exceptional combination of properties and has a machined surface. the terms
machined surface
herein refer to a surface of an article which has been processed to, for example, a desired shape or geometry; mechanical processing may be employed. machining processes include, but are not limited to, lathe turning, milling and broaching .
the compositional range of the nickel base superalloy article, in weight percent, is 2. 2al, 4. 6ti, 15. 5cr, 3. 0mo, 13. 5co, 0. 015c, 0. 015b, 0. 04zr, 0. 001 - 0. 005mg, balance ni and unavoidable impurities .
superalloy articles of the invention may be conventionally fabricated. preferably, the articles are fabricated as follows: a casting of the desired composition is made by vacuum induction melting followed by vacuum arc remelting. the cast material is then preferably processed in accordance with one of two primary schemes or combination thereof, as described in u. s. patent 5, 120, 373 .
as also described in u. s. patent 5, 120, 373, the material may alternately be hot worked at a temperature above the gamma prime solvus. it is also possible to accomplish this initial hot working operation using a combination of steps above and below the gamma prime solvus in conjunction with appropriate combinations of intermediate hypersolvus or supersolvus treatments .
after the material has been deformed an amount in excess of 0. 5 cumulative true strain, it is given an overage treatment to produce a significantly enlarged gamma prime particle size over that which would normally be present. the resultant microstructure is termed
overaged .
the overaging process is similar to that which is described in u. s. patent 4, 574, 015. the overaging process consists of cooling the material at a rate of less than about 100°f (56°c) and preferably 50°f (28°c) per hour, (and most preferably less than 20°f (11°c) per hour) through the gamma prime solvus. the resultant coarsened gamma prime particle size will be in excess of 1µm and preferably in excess of 2µm .
this overaged material is then further hot deformed an amount in excess of that required to produce a cumulative true strain of 0. 9, and preferably a true cumulative strain of at least 1. 6. this strain does not include that undergone before the overage treatment. a strain rate of at least about 0. 1 in / in / min (1. 6x10 - 3 s - 1) is employed. this further deformation is accomplished below the gamma prime solvus (but within 200°f (111°c) ) and without intermediate anneals. intermediate anneals may be performed at temperatures below but within 200°f (111°c) of the gamma prime solvus temperature .
the resultant material, as processed in accordance with the above description, will have an exceptionally fine grain size, predominately finer than astm grain size 10 and preferably on the order of astm 12 or finer .
the volume fraction of gamma prime present in the alloy of the present invention is between 35 - 45 percent, depending upon the amount of aluminium and titanium employed in the composition .
the inventive material also includes a plurality of discrete mc carbides. the diameter of the discrete carbides may be between about 0. 0005 inches (12. 7µm) and about 0. 0025 inches (63. 5µm). diameters on the order of between about 0. 0006 inches (15. 2µm) and about 0. 0007 inches (17. 8µm) may often be present. the resultant material is further characterized by an absence of carbide stringers .
applicant has also determined that in addition to controlling the amount of molybdenum present in the mc carbides, the amount of carbon must also be controlled such that discrete carbides form, as opposed to detrimental carbide stringers. this is possible by controlling the amount of carbon in the superalloy composition to 0. 015 weight percent. as a result of the invention, discrete carbides of carbon and predominantly titanium result .
a nickel base superalloy material known as pwa 1113 (nominal composition, in weight percent, of 2. 2al, 4. 6ti, 16. 3cr, 4. 2mo, 13. 5co, 0. 032c, 0. 006b, 0. 07zr, 0. 0025mg balance ni) and regarded as among the best prior art high strength, nickel base superalloys used for components such as shafts, seals and disks was processed in accordance with the teachings of u. s. patent no. 5, 120, 373. the superalloy material of the invention (2. 2al, 4. 6ti, 15. 5cr, 3mo, 13. 5co, 0. 015c, 0. 015b, 0. 04zr, 0. 0025mg, bal ni) was also processed by method disclosed therein .
an advantage of the invention is that the operating stress on components fabricated from the invention can be raised approximately five percent while maintaining the same cyclic fatigue life as the prior art alloy. a corresponding reduction in component weight may then also be achieved .
the superalloy material of the invention, as described in example 1, was subjected to conventional ultimate tensile strength testing at various temperatures. this material exhibited high strength, as detailed in table 1 below .
an advantage of the invention is that superalloy articles of the invention comprise a plurality of discrete carbides essentially free from molybdenum for increased fatigue strength. applicant has discovered that a significant improvement in low cycle fatigue strength can be obtained if molybdenum is essentially eliminated from the carbides. molybdenum' s adverse effect on low cycle fatigue strength in machined articles has never before been appreciated or understood .
thus, the present invention provides a machined surface of a nickel base superalloy article which is suitable for hot deformed gas turbine engine components such as shafts and disks, wherein the machined surface is not damaged during conventional tungsten carbide lathe turning such that the article of finished geometry possesses superior low cycle fatigue strength .
a hot deformed nickel base superalloy article having a machined surface, said superalloy article comprising a composition, in weight percent, of 2. 2al, 4. 6ti, 15. 5cr, 3. 0mo, 13. 5co, 0. 015c, 0. 015b, 0. 04zr, 0. 001 - 0. 005mg, balance ni and unavoidable impurities, said superalloy article being free of carbide stringers and further comprising a plurality of discrete mc carbides, where m is predominantly titanium and c is carbon, which are free from molybdenum for increased fatigue strength .
e. f. bradley
superalloys - a technical guide
, p. 9 asm international ohio, usa, november 1989, isbn 0 - 87170327
r. t. holt and w. wallace :
impurities and trace elements in nickel - base superalloys
international metals reviews, review 203, march 1976, pages 1 - 24
lapsed in a contracting state announced via postgrant inform. from nat. office to epo
a process for producing a fine grain forged superalloy article having a high yield strength at intermediate temperatures. a preferred starting composition comprises, by weight, 15% cr, 13. 6% co, 4. 1% mo, 4. 6% ti, 2. 2% al, 0. 01% c, 0. 007% b, 0. 07% zr, balance ni. this material is forged at a temperature above the gamma prime solvus and at a true strain of at least 0. 5. alternately, the material may be forged below the gamma prime solvus temperature with intermediate super solvus anneals. the overaged material is then worked at a temperature below the gamma prime solvus. the resultant fine grain material is then heat treated or can be further isothermally forged prior to heat treatment to produce complex shapes .
this application is a continuation of application ser. no. 07 / 991, 084, filed dec. 14, 1992, now abandoned, which is a continuation of application ser. no. 07 / 685, 581, filed apr. 15, 1991, and now abandoned .
the present invention relates to a process for forging superalloys within a particular composition range. the resultant material is fine grained and has good intermediate temperature mechanical properties. the fine grain material may also be further processed by isothermal forging .
nickel base superalloys are widely used in gas turbine engines and have evolved greatly over the last 50 years. as used herein the term superalloy will mean a nickel base superalloy containing a substantial amount of the gamma prime (ni 3 al) strengthening phase, preferably from about 30 to about 50 volume percent of the gamma prime phase .
processing techniques for superalloys have also evolved and many of the newer processes are quite costly .
u. s. pat. no. 3, 519, 503 describes an isothermal forging process for producing complex superalloy shapes. this process is currently widely used, and as currently practiced requires that the starting material be produced by powder metallurgy techniques. the reliance on powder metallurgy techniques makes this process expensive .
u. s. pat. no. 4, 574, 015 deals with a method for improving the forgeability of superalloys by producing overaged microstructures in such alloys. the gamma prime phase particle size is greatly increased over that which would normally be observed .
u. s. pat. no. 4, 579, 602 deals with a superalloy forging sequence which involves an overage heat treatment .
u. s. pat. no. 4, 769, 087 describes another forging sequence for superalloys which includes an overage step .
u. s. pat. no. 4, 612, 062 describes a forging sequence for producing a fine grained article from a nickel base superalloy. the process includes a first deformation step at a temperature above the gamma prime solvus and a second deformation step at a temperature below the gamma prime solvus with specified strain rates and deformation amounts .
u. s. pat. no. 4, 453, 985 describes an isothermal forging process which produces a fine grain product .
u. s. pat. no. 2, 977, 222 describes a class of superalloys which are similar to those to which the invention process has particular applicability .
the present invention provides a process for producing a fine grained article and is especially appropriate for use with a specified range of alloy compositions. the resultant fine grained material may be used in its fine grained condition for articles which require high strength, particularly high yield strength at intermediate temperatures, or this fine grained material may be used as a forging preform for conversion by isothermal or hot die forging into complex shapes. table i lists broad, intermediate and preferred composition ranges .
table i _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ compositional ranges (by weight percent) broad intermediate preferred _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ cr 12 - 20 12 - 20 13 - 18co 10 - 20 10 - 20 10 - 15mo 2 - 5. 5 2 - 5. 5 3 - 5ti 3 - 7 3. 5 - 7 3. 6 - 5. 6al 1. 2 - 3. 5 1. 2 - 3. 5 1. 7 - 2. 7c. 005 -. 25. sup. (1). 005 -. 15. sup. (1). 01 -. 13. sup. (1) b. 005 -. 05. 005 -. 05. 005 -. 05zr. 01 -. 1. 01 -. 1. 01 -. 1ta 0 - 1 - - - - w 0 - 4. 5 0 - 2. 5 - - nb 0 - 1 - - - - fe 0 - 2. 0 0 - 2. 0 0 -. 5hf 0 -. 3 - - - - y 0 -. 02 - - - - v 0 -. 1 - - - - re 0 - 1. 0 - - - - ni bal bal bal _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (1) an upper c limit of about. 013% is preferred for applications where fatigue resistance is critical
fig. 1 is a block diagram which broadly sets out the invention process. as can be seen in fig. 1, the process starts with a casting of the desired composition which preferably has a relatively fine grain size. after homogenization, the cast material may be processed according to two primary schemes or combinations thereof. according to one scheme, the left branch of the fig. 1 diagram, the cast material is deformed at elevated temperatures but below the gamma prime solvus so that gamma prime phase dissolution is minimized or even eliminated. subsolvus anneals or reheat treatments may be employed to maintain billet temperature, affect recrystallization, while avoiding or minimizing gamma prime phase dissolution. in additional, super - solvus anneals or reheat treatments may be employed to produce extensive or complete gamma prime phase dissolution in conjunction with extensive or complete recrystallization. the total amount of work required will be equivalent to that required to produce at least 0. 5 and preferably at least 0. 9 cumulative true strain. this cumulative true strain may be obtained from combined hot deformation operations including upsetting and drawing. during upsetting an average strain rate of at least about 0. 1 in / in / min. is preferred. during drawing an average strain rate of at least about 0. 5 in / in / min is preferred. to perform this amount of work on a cast superalloy material at a temperature below the gamma prime solvus, it will undoubtedly be necessary to use multiple deformation steps with intermediate anneals above the gamma prime solvus, to prevent cracking .
according to the right branch of fig. 1, the material may alternately be hot worked at a temperature above the gamma prime solvus .
it is also, of course, possible to accomplish this initial hot working operation using a combination of steps above and below the gamma prime solvus in conjunction with appropriate combinations of intermediate hypersolvus or subsolvus treatments .
after the material has been deformed an amount in excess of 0. 5 cumulative true strain, it is given an overage treatment to produce a significantly enlarged gamma prime particle size over that which would normally be present. the resultant microstructure is termed
overaged
. the overaging process is similar to that described in u. s. pat. no. 4, 574, 015 and consists of cooling the material at a rate of less than about 100° f. and preferably 50° f. per hour, (and most preferably less than 20° f. per hour) through the gamma prime solvus. the resultant coarsened gamma prime particle size will be in excess of 1 micron and preferably in excess of 2 microns .
this overaged material is then further hot deformed an amount in excess of that required to produce a cumulative true strain of 0. 9, and preferably a true cumulative strain of 1. 6. this strain does not include that undergone before the overage treatment. a strain rate of at least about 0. 1 in / in / min is employed. this further deformation is accomplished below the gamma prime solvus (but within 200° f .) and without intermediate anneals. intermediate reheats may be performed at temperatures below but within 200° f. of the gamma prime solvus temperature. the resultant material will have an exceptionally fine grain size, predominately finer than astm grain size 10 and usually on the order of astm 14 or finer. astm grain sizes are listed in table ii .
table ii _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ avg. grain astm dia. / mm _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2. 18 4. 091 6. 044 8. 022 10. 011 12. 006 14. 003 16. 0015 18. 0007 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
depending on the size and contour of the article, some larger unrecrystallized grains may remain at the very center of the article where the effective amount of deformation was insufficient to promote full recrystallization. such unrecrystallized regions usually comprise less than 10% by volume of the material .
the combination of the invention process and the preferred composition reliability results in material with an astm 12 - 18 grain size, the finest grain size we have ever observed in production superalloys. the fine grain size contributes to increased strength, ductility and toughness at temperatures up to at least 1200° f. the fine grain size also provides a significant enhancement in ultrasonic nondestructive testing sensitivity. small defects can be detected at increased depths relative to coarse grained material.
waspaloy is a registered trademark of united technologies corp that refers to an age hardening austenitic ( face-centred cubic ) nickel-based superalloy . waspaloy alloy is typically used in high temperature applications , particularly in gas turbines . 
waspaloy is a registered trademark of united technologies corp that refers to an age hardening austenitic (face-centred cubic) nickel-based superalloy. waspaloy alloy is typically used in high temperature applications, particularly in gas turbines.
waspaloy is a registered trademark of united technologies corp that refers to an age hardening austenitic (face-centred cubic) nickel-based superalloy. waspaloy alloy is typically used in high temperature applications, particularly in gas turbines.