EP0533914B1 - Superalloy forging process and related composition - Google Patents
Superalloy forging process and related composition Download PDFInfo
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- EP0533914B1 EP0533914B1 EP92911977A EP92911977A EP0533914B1 EP 0533914 B1 EP0533914 B1 EP 0533914B1 EP 92911977 A EP92911977 A EP 92911977A EP 92911977 A EP92911977 A EP 92911977A EP 0533914 B1 EP0533914 B1 EP 0533914B1
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- gamma prime
- temperature
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C19/00—Alloys based on nickel or cobalt
- C22C19/03—Alloys based on nickel or cobalt based on nickel
- C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
- C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
- C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
Definitions
- the present invention concerns a process for producing an article having a fine grain size and good mechanical properties.
- 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.
- 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.
- US-A 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.
- US-A 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.
- US-A 4,579,602 deals with a superalloy forging sequence which involves an overage heat treatment.
- US-A 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.
- US-A 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.
- 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 US-A 2,977,222, 4,083,734, and 4,957,567.
- 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, .05% C, .007% B, .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.
- 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.
- Figure 1 is a block diagram which broadly sets out the invention process.
- the process starts with a casting of the desired composition which preferably has a relatively fine grain size.
- the cast material may be processed according to two primary schemes or combinations thereof. According to one scheme, the left branch of the Figure 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.
- 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 .5 and preferably at least .9 cumulative true strain.
- This cumulative true strain may be obtained from combined hot deformation operations including upsetting and drawing.
- upsetting an average strain rate of at least 0.1 cm/cm/min (0.1 in/in/min) is preferred.
- drawing an average strain rate of at least 0.5 cm/cm/min (0.5 in/in/min) is preferred.
- the material may alternately be hot worked at a temperature above the gamma prime solvus.
- the overaging process is similar to that described in US-A 4,574,015 and consists of cooling the material at a rate of less than 55°C (100°F) and preferably 28°C (50°F) per hour, (and most preferably less than 11°C (20°) per hour) through the gamma prime solvus.
- the resultant coarsened gamma prime particle size will be in excess of 1 ⁇ m (1 micron) and preferably in excess of 2 ⁇ m (2 microns).
- This overaged material is then further hot deformed an amount in excess of that required to produce a cumulative true strain of .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 0.1 cm/cm/bin (0.1 in/in/min) is employed. This further deformation is accomplished below the gamma prime solvus (but within 110°C (200°F) and without intermediate anneals. Intermediate reheats may be performed at temperatures below but within 110°C (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 ASTM Avg. Grain 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 650°C (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.
- This exceptionally fine grained superalloy material is adapted to be used at temperatures up to 650°C (1200°F).
- This fine grained material is also suitable to be isothermally or hot die forged to produce complex articles according to the teachings of US-A 3,519,503.
- the processing steps described heretofore in this application provide a material which is "conditioned” as described in US-A- 3,519,503 and which may be forged according to the teachings of that patent.
- FIG. 1 is a block diagram showing the essential steps of the invention process.
- Figure 2 is a block diagram showing the steps of a preferred embodiment of the invention.
- Figure 3 is a plot of yield strength versus temperature for the invention material and several prior art materials.
- Figure 4 is a bar graph of flow stress versus temperature for the invention material in the fine grain condition.
- Figure 5 is a bar graph of elongation versus temperature for the invention material in the fine grain condition.
- Figure 2 is a block diagram of a process particularly adapted to produce disk preforms and shafts for gas turbine engines.
- vacuum induction material material whose composition falls within the scope of Table I is first vacuum induction melted.
- vacuum induction material was produced as a 54 cm (21 inch) diamter cylinder. This material is then vacuum arc remelted to Droduce a cylindrical casting having a 61cm (24inch) diameter and a grain size on the order of 1.59 to 3.18 mn (1/16 to 1/8 inch).
- the preferred compositions are essentially free from the heavier refractory metals such as tungsten and tantalum which can interfere with the production of fine grain sized unsegregated material.
- this 61cm (24 inch) diameter vacuum arc remelted material was then coated with a glass ceramic coating (Ceramguard 11, a product of A.D. Smith Co. of Florence, Kentucky).
- This coated casting was soaked at 1190°C (2175°F) for 72 hours and was encased in a mild steel can having a 6.4 mm (1/4 inch) thickness.
- the glass ceramic coating serves as a lubricant and prevents the steel can from interacting with the superalloy material.
- the steel can reduces cracking during initial hot deformation in part because it reduces chilling of the workpiece surface by the die.
- the order of the coating, homogenization and canning operations is not critical except that coating must precede canning, and if mild steel is used for the canning material, homogenization must precede canning because the canning material will not survive the homogenization conditions.
- the casting was then upset, in the axial direction, between flat dies at a temperature of 1190°C (2175°F) to reduce the length of the cylinder and increase the diameter of the cylinder from 61cm (24inches)to 81 cm (32 inches) in diameter at a strain rate of 0.5cm/cm/min (0.5 in/in/min). This results in a true strain of -.58.
- the gamma prime solvus for the material used was between 1110°C and 1121°C (2030°F and 2050°F) the soaking and upset operations were performed above the gamma prime solvus temperature.
- the 81 cm (32inch) diameter material was then press forged radially between flat dies at a temperature of 1093°C (2000°F) below the gamma prime solvus temperature) to reduce the diameter from 81cm (32inches) to 61cm (24 inches) at a rate of 0.5 cm/cm/min (0.5 in/in/min). Note that the diameter at this point was the same as the starting diameter but the material had been subjected to a total cumulative true strain of about 1.16.
- the absolute values of strains are added since redundant strain is useful in achieving the necessary microstructure.
- the material was then heated to 1177°C (2150°F) (above the gamma prime solvus temperature) and was soaked at this temperature for 4 hours.
- the hot forging was then immediately transferred to another furnace at a temperature of 1080°C (1975°F) and held in that furnace for a period of six hours.
- the material (which started as a single phase material with no gamma prime phase), gradually passed through the gamma prime solvus temperature at a rate of 11°C (20°F) per hour gamma prime particles were precipitated.
- the precipitated gamma prime particles coarsened to a size predominantly in excess of 1 um (1 micron).
- the resultant structure was greatly overaged, meaning that the gamma prime particle size and spacing were much in excess of that which provides optimum mechanical properties. While two different temperature furnaces were used, it is apparent that a programmable furnace could also be utilized or that the furnace temperature could be manually reduced to produce the same result.
- the 61 cm (24 inch)diameter overaged forging was then press forged, using flat dies, at a temperature of 1080°C (1975°F) to a diameter of 41cm (16inches), producing a true strain of .81 at a strain rate of 0.5cm/cm/min (0.5 in/in/min).
- the material was then reheated at a temperature of 1080°C (1975°F) and rotary forged with intermediate 1080°C (1975°F) reheats to a final diameter of 18cm (7inches).
- Rotary forging was performed in a GFM machine, by a rotary forging or swaging machine which is the product of GFM Holdings of Steyr, Austria and is described in US-A 4,430,881, 3,889,514, and 3,871,223. Pairs of diametrically opposed hammers strike the workpiece repeatedly, as the workpiece is rotated. Other deformation techniques could have been employed.
- the true strain which results from converting the ingot from 41cm (16inches) diameter to 18cm (7 inches) diameter is about 1.65 and the strain rate is at least 3cm/cm/min (3 in/in/min).
- the 18cm (7 inch) diameter billet had a grain size of about ASTM 12-14, except for the central 5.0-7.6 cm (2-3 inches)which showed about 10% larger unrecrystallized grains.
- the resultant material with a diameter of 18 cm (7 inches)was ideally suited (after further machining and heat treatment) for use as a hollow shaft in a high thrust gas turbine engine application.
- Such shafts are used to transmit power from the turbine section forward to the compressor section and are required to have a high torque transmission capability.
- Figure 3 shows yield strength as a function of temperature for several nickel base superalloys and for a high strength steel material (17-22A) which is conventionally used for gas turbine engine shafts.
- the invention process material has the highest yield strength up to about 538°C (1000°F) of any of the materials tested.
- the material listed as IN 100 has a nominal composition of 12% Cr, 18% Co, 3.2% Mo, 4.3% Ti, 5.0% Al, .8% V, 0.07% C, 0.02% B, 0.06% Zr, balance Ni, and is one of the highest strength superalloys in common use.
- IN 100 has a gamma prime fraction of about 65% and is not reliably processable by the present invention, but instead must be processed using more costly powder metallurgical processing techniques.
- the material listed as Inconel 718 has a nominal composition of 19% Cr, 3.1% Mo, 5.3% (Cb+Ta), 0.9% Ti, 0.6% Al, 19% Fe, balance Ni, and a grain size of about ASTM 6, and it can be seen to have a yield strength which is 138 MPa (20ksi) less than that of the invention processed material with the debit in yield strength increasing with increasing temperature.
- the material labeled as coarse grained Waspaloy has a nominal composition of 19.5% Cr, 13.5% Co, 4.2% Mo, 3.0% Ti, 1.4% Al, 0.05% C, 0.006% B, 0.007% Zr, balance Ni, and grain size of approximately ASTM 4 and it has a yield strength which is approximately 207 MPa (30 ksi) less than that of the invention processed material, with the debit in yield strength diminishing with increasing temperature.
- the material listed as steel has a nominal composition of .45% C, .55% Mn, .28% Si, .95% Cr, .55% Mo, .3% V, balance Fe, and was tested in the normalized and tempered (N+T) condition and the quenched and tempered (Q+T) condition.
- the normalized and tempered material can be seen to have a yield strength which is 414-483 MPa (60-70 ksi) less than that of the invention material, and to have a yield strength which drops sharply at temperatures above 316°C (600°F).
- the quenched and tempered material strength drops sharply above 204°C (400°F). Accordingly it can be seen that of these candidate materials, the present invention material displays a superior yield strength over a wide range of temperatures and is useful at temperatures up to at least 649°C (1200°F).
- the invention material in its fine grained form also displays useful super plastic properties over a fairly wide temperature range and can therefore be isothermally or hot die forged at relatively low forging stresses to form complex shapes.
- Figure 4 shows the flow stress of this material when measured in a tensile test at a strain rate of 0.1 cm/cm/min (0.1 in/in/min) at several different temperatures, and it can be seen that for temperature between 1010°C (1850°F) and 1107°C (2025°F), the invention processed material has a flow stress of less than 69 MPa (10 ksi).
- Figure 5 shows the tensile elongation results for the same material in tensile tests performed at 0.1 cm/cm/min (0.1 in/in/min), and it can be seen that at between 1010°C and 1080°C (1850°F and 1975°F) the invention material displayed more than about 150% tensile elongation. This indicates a capability of being formed into complex shapes without cracking.
- hot die forging means a process in which the forging dies are heated to within 280°C (500°F) of the forging temperature and isothermal forging means that the dies are heated to within 110°C (200°F) of the forging temperature.
- the preferred composition has been selected to display the super plastic behavior needed for hot die or isothermal forging over a useful temperature range. Not all compositions in the broad range will display such behavior but the skilled artisan will readily be able to determine if a composition has the behavior by simple hot tensile tests.
- the material is suitable for hot die or isothermal forging at a strain rate on the order of 0.05-0.2 cm/cm/min (0.05-0.2 in/in/min) to form complex shapes such as gas turbine engine disks.
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Abstract
Description
- The present invention concerns a process for producing an article having a fine grain size and good mechanical properties.
- 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 (Ni3Al) 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.
- US-A 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.
- US-A 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.
- US-A 4,579,602 deals with a superalloy forging sequence which involves an overage heat treatment.
- US-A 4,769,087 describes another forging sequence for superalloys which includes an overage step.
- US-A 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.
- US-A 4,453,985 describes an isothermal forging process which produces a fine grain product.
- US-A 2,977,222 describes a class of superalloys which are similar to those to which the invention process has particular applicability.
- The process of the present invention for producing an article having a fine grain size and good mechanical properties is described in claim 1.
- Preferred embodiments of the claimed process are given in the dependent claims.
- 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 13-18 Co 10-20 10-20 10-15 Mo 2-5.5 2-5.5 3-5 Ti 3-7 3.5-7 3.6-5.6 Al 1.2-3.5 1.2-3.5 1.7-2.7 C .005-.25(1) .005-.15(1) .01-.13(1) B .005-.05 .005-.05 .005-.05 Zr .01-.1 .01-.1 .01-.1 Ta 0-1 -- -- W 0-4.5 0-2.5 -- Nb 0-1 -- -- Fe 0-2.0 0-2.0 0-.5 Hf 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 - 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 US-A 2,977,222, 4,083,734, and 4,957,567.
- 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, .05% C, .007% B, .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.
- 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.
- Figure 1 is a block diagram which broadly sets out the invention process. As can be seen in Figure 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 Figure 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 .5 and preferably at least .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 0.1 cm/cm/min (0.1 in/in/min) is preferred. During drawing an average strain rate of at least 0.5 cm/cm/min (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 Figure 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 .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 US-A 4,574,015 and consists of cooling the material at a rate of less than 55°C (100°F) and preferably 28°C (50°F) per hour, (and most preferably less than 11°C (20°) per hour) through the gamma prime solvus. The resultant coarsened gamma prime particle size will be in excess of 1 µm (1 micron) and preferably in excess of 2 µm (2 microns).
- This overaged material is then further hot deformed an amount in excess of that required to produce a cumulative true strain of .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 0.1 cm/cm/bin (0.1 in/in/min) is employed. This further deformation is accomplished below the gamma prime solvus (but within 110°C (200°F) and without intermediate anneals. Intermediate reheats may be performed at temperatures below but within 110°C (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 ASTM Avg. Grain Dia./mm 2 .18 4 .091 6 .044 8 .022 10 .011 12 .006 14 .003 16 .0015 18 .0007 - 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 650°C (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.
- This exceptionally fine grained superalloy material is adapted to be used at temperatures up to 650°C (1200°F).
- 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.
- This fine grained material is also suitable to be isothermally or hot die forged to produce complex articles according to the teachings of US-A 3,519,503. The processing steps described heretofore in this application provide a material which is "conditioned" as described in US-A- 3,519,503 and which may be forged according to the teachings of that patent.
- The foregoing, and other features and advantages of the present invention will become more apparent from the following description and accompanying drawings.
- Figure 1 is a block diagram showing the essential steps of the invention process.
- Figure 2 is a block diagram showing the steps of a preferred embodiment of the invention.
- Figure 3 is a plot of yield strength versus temperature for the invention material and several prior art materials.
- Figure 4 is a bar graph of flow stress versus temperature for the invention material in the fine grain condition.
- Figure 5 is a bar graph of elongation versus temperature for the invention material in the fine grain condition.
- One preferred form of the present invention will be described with reference to Figure 2 which is a block diagram of a process particularly adapted to produce disk preforms and shafts for gas turbine engines.
- According to the process shown in Fig. 2, material whose composition falls within the scope of Table I is first vacuum induction melted. In a particular actual example, vacuum induction material was produced as a 54 cm (21 inch) diamter cylinder. This material is then vacuum arc remelted to Droduce a cylindrical casting having a 61cm (24inch) diameter and a grain size on the order of 1.59 to 3.18 mn (1/16 to 1/8 inch). In this respect it should be noted that the preferred compositions are essentially free from the heavier refractory metals such as tungsten and tantalum which can interfere with the production of fine grain sized unsegregated material.
- In the preferred embodiment this 61cm (24 inch) diameter vacuum arc remelted material was then coated with a glass ceramic coating (Ceramguard 11, a product of A.D. Smith Co. of Florence, Kentucky). This coated casting was soaked at 1190°C (2175°F) for 72 hours and was encased in a mild steel can having a 6.4 mm (1/4 inch) thickness. The glass ceramic coating serves as a lubricant and prevents the steel can from interacting with the superalloy material. The steel can reduces cracking during initial hot deformation in part because it reduces chilling of the workpiece surface by the die. The order of the coating, homogenization and canning operations is not critical except that coating must precede canning, and if mild steel is used for the canning material, homogenization must precede canning because the canning material will not survive the homogenization conditions.
- The casting was then upset, in the axial direction, between flat dies at a temperature of 1190°C (2175°F) to reduce the length of the cylinder and increase the diameter of the cylinder from 61cm (24inches)to 81 cm (32 inches) in diameter at a strain rate of 0.5cm/cm/min (0.5 in/in/min). This results in a true strain of -.58.
- Since the gamma prime solvus for the material used was between 1110°C and 1121°C (2030°F and 2050°F) the soaking and upset operations were performed above the gamma prime solvus temperature. The 81 cm (32inch) diameter material was then press forged radially between flat dies at a temperature of 1093°C (2000°F) below the gamma prime solvus temperature) to reduce the diameter from 81cm (32inches) to 61cm (24 inches) at a rate of 0.5 cm/cm/min (0.5 in/in/min). Note that the diameter at this point was the same as the starting diameter but the material had been subjected to a total cumulative true strain of about 1.16. The absolute values of strains are added since redundant strain is useful in achieving the necessary microstructure. The material was then heated to 1177°C (2150°F) (above the gamma prime solvus temperature) and was soaked at this temperature for 4 hours. The hot forging was then immediately transferred to another furnace at a temperature of 1080°C (1975°F) and held in that furnace for a period of six hours. During the time in the lower temperature furnace, the material (which started as a single phase material with no gamma prime phase), gradually passed through the gamma prime solvus temperature at a rate of 11°C (20°F) per hour gamma prime particles were precipitated. Because of the elevated temperature and long times involved, the precipitated gamma prime particles coarsened to a size predominantly in excess of 1 um (1 micron). The resultant structure was greatly overaged, meaning that the gamma prime particle size and spacing were much in excess of that which provides optimum mechanical properties. While two different temperature furnaces were used, it is apparent that a programmable furnace could also be utilized or that the furnace temperature could be manually reduced to produce the same result. The 61 cm (24 inch)diameter overaged forging was then press forged, using flat dies, at a temperature of 1080°C (1975°F) to a diameter of 41cm (16inches), producing a true strain of .81 at a strain rate of 0.5cm/cm/min (0.5 in/in/min). The material was then reheated at a temperature of 1080°C (1975°F) and rotary forged with intermediate 1080°C (1975°F) reheats to a final diameter of 18cm (7inches). Rotary forging was performed in a GFM machine, by a rotary forging or swaging machine which is the product of GFM Holdings of Steyr, Austria and is described in US-A 4,430,881, 3,889,514, and 3,871,223. Pairs of diametrically opposed hammers strike the workpiece repeatedly, as the workpiece is rotated. Other deformation techniques could have been employed. The true strain which results from converting the ingot from 41cm (16inches) diameter to 18cm (7 inches) diameter is about 1.65 and the strain rate is at least 3cm/cm/min (3 in/in/min). The 18cm (7 inch) diameter billet had a grain size of about ASTM 12-14, except for the central 5.0-7.6 cm (2-3 inches)which showed about 10% larger unrecrystallized grains.
- The resultant material, with a diameter of 18 cm (7 inches)was ideally suited (after further machining and heat treatment) for use as a hollow shaft in a high thrust gas turbine engine application. Such shafts are used to transmit power from the turbine section forward to the compressor section and are required to have a high torque transmission capability.
- The material property which is most associated with torque transmission capability in this type of application is yield strength. Figure 3 shows yield strength as a function of temperature for several nickel base superalloys and for a high strength steel material (17-22A) which is conventionally used for gas turbine engine shafts.
- It can be seen that the invention process material has the highest yield strength up to about 538°C (1000°F) of any of the materials tested. The material listed as
IN 100 has a nominal composition of 12% Cr, 18% Co, 3.2% Mo, 4.3% Ti, 5.0% Al, .8% V, 0.07% C, 0.02% B, 0.06% Zr, balance Ni, and is one of the highest strength superalloys in common use. IN 100 has a gamma prime fraction of about 65% and is not reliably processable by the present invention, but instead must be processed using more costly powder metallurgical processing techniques. The material listed as Inconel 718 has a nominal composition of 19% Cr, 3.1% Mo, 5.3% (Cb+Ta), 0.9% Ti, 0.6% Al, 19% Fe, balance Ni, and a grain size of about ASTM 6, and it can be seen to have a yield strength which is 138 MPa (20ksi) less than that of the invention processed material with the debit in yield strength increasing with increasing temperature. The material labeled as coarse grained Waspaloy has a nominal composition of 19.5% Cr, 13.5% Co, 4.2% Mo, 3.0% Ti, 1.4% Al, 0.05% C, 0.006% B, 0.007% Zr, balance Ni, and grain size of approximately ASTM 4 and it has a yield strength which is approximately 207 MPa (30 ksi) less than that of the invention processed material, with the debit in yield strength diminishing with increasing temperature. The material listed as steel has a nominal composition of .45% C, .55% Mn, .28% Si, .95% Cr, .55% Mo, .3% V, balance Fe, and was tested in the normalized and tempered (N+T) condition and the quenched and tempered (Q+T) condition. The normalized and tempered material can be seen to have a yield strength which is 414-483 MPa (60-70 ksi) less than that of the invention material, and to have a yield strength which drops sharply at temperatures above 316°C (600°F). The quenched and tempered material strength drops sharply above 204°C (400°F). Accordingly it can be seen that of these candidate materials, the present invention material displays a superior yield strength over a wide range of temperatures and is useful at temperatures up to at least 649°C (1200°F). - The invention material in its fine grained form also displays useful super plastic properties over a fairly wide temperature range and can therefore be isothermally or hot die forged at relatively low forging stresses to form complex shapes. Figure 4 shows the flow stress of this material when measured in a tensile test at a strain rate of 0.1 cm/cm/min (0.1 in/in/min) at several different temperatures, and it can be seen that for temperature between 1010°C (1850°F) and 1107°C (2025°F), the invention processed material has a flow stress of less than 69 MPa (10 ksi). Figure 5 shows the tensile elongation results for the same material in tensile tests performed at 0.1 cm/cm/min (0.1 in/in/min), and it can be seen that at between 1010°C and 1080°C (1850°F and 1975°F) the invention material displayed more than about 150% tensile elongation. This indicates a capability of being formed into complex shapes without cracking.
- In this context hot die forging means a process in which the forging dies are heated to within 280°C (500°F) of the forging temperature and isothermal forging means that the dies are heated to within 110°C (200°F) of the forging temperature.
- The preferred composition has been selected to display the super plastic behavior needed for hot die or isothermal forging over a useful temperature range. Not all compositions in the broad range will display such behavior but the skilled artisan will readily be able to determine if a composition has the behavior by simple hot tensile tests.
- Returning briefly to Figure 2, the flow chart for the practical embodiment of the present invention, after the GFM forging operation the material is suitable for hot die or isothermal forging at a strain rate on the order of 0.05-0.2 cm/cm/min (0.05-0.2 in/in/min) to form complex shapes such as gas turbine engine disks.
Claims (6)
- Process for producing an article having a fine grain size and good mechanical properties at temperatures below 650°C (1200°F), starting with a material consisting of 12-20% Cr, 10-20% Co, 2-5.5% Mo, 3-7% Ti, 1.2-3.5% Al, .005-.25% C, .005-.05% B, .01-.1% Zr, 0-1% Ta, 0-4.5% W, O-1% Nb, 0-2.0% Fe, 0-.3% Hf, 0-.02% Y, 0-.1% V, 0-1.0% Re, balance Ni, plus incidental impurities and having a gamma prime solvus temperature, including the steps of:a) working the material in at least one step selected from the group consisting of (i) working above the gamma prime solvus, (ii) working below the gamma prime solvus and annealing, and (iii) mixtures thereof, said at least one step producing a cumulative true strain of at least .5 and, at a strain rate of at least 0.1 cm/cm/min (0.1 in/in/min);b)heating said worked material to a temperature above the gamma prime solvus and cooling said worked material through the gamma prime solvus, at a rate of less than 55°C (100°F) per hour to provide an overaged microstructure; andc)hot working the material below the gamma prime solvus temperature but within 110°C (200°F), to produce a total strain of at least .9 and at a strain rate of at least 0.1 cm/cm/min (0.1 in/in/min),whereby the resultant material has a grain size of 0.011 mm (an ASTM grain size of 10) or finer.
- A process as in claim 1 further including the step of hot die forging the fine grain material at a strain rate of from .05 to .2 cm/cm/min (in/in/min).
- A process as in claim 1 wherein the material consists of 12-20% Cr, 10-20% Co, 2-5.5% Mo, 3.5-7% Ti, 1.2-3.5% Al, .005-.15% C, .005-.05% B, .01-.1% Zr, 0-2.5% W, 0-2.0% Fe, balance Ni, plus incidental impurities.
- A process as in any of claims 1 or 2 wherein the material consists of 13-18% Cr, 10-15% Co, 3-5% Mo, 3.6-5.6% Ti, 1.7-2.7% Al, .01-.1% C, .005-.05% B, .01-.1% Zr, 0-.5% Fe, balance Ni, plus incidental impurities.
- A process as in claim 1 wherein the material consists of 12-20% Cr, 10-20% Co, 2-5.5% Mo, 3.5-7% Ti, 1.2-3.5% Al, .005-.15% C, .005-.05% B, .01-.1% Zr, 0-2.5% W, 0-2.0% Fe, balance Ni, plus incidental impurities.
- A process as in claim 1 or claim 2 wherein the material is cooled through the gamma prime solvus at less than 10°C per hour (20°F per hour).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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US68558191A | 1991-04-15 | 1991-04-15 | |
US685581 | 1991-04-15 | ||
PCT/US1992/003082 WO1992018659A1 (en) | 1991-04-15 | 1992-04-15 | Superalloy forging process and related composition |
Publications (2)
Publication Number | Publication Date |
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EP0533914A1 EP0533914A1 (en) | 1993-03-31 |
EP0533914B1 true EP0533914B1 (en) | 1997-03-12 |
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Application Number | Title | Priority Date | Filing Date |
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EP92911977A Expired - Lifetime EP0533914B1 (en) | 1991-04-15 | 1992-04-15 | Superalloy forging process and related composition |
Country Status (5)
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EP (1) | EP0533914B1 (en) |
JP (1) | JP3073525B2 (en) |
KR (1) | KR100187794B1 (en) |
DE (1) | DE69218089T2 (en) |
WO (1) | WO1992018659A1 (en) |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
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US5693159A (en) * | 1991-04-15 | 1997-12-02 | United Technologies Corporation | Superalloy forging process |
US5593519A (en) * | 1994-07-07 | 1997-01-14 | General Electric Company | Supersolvus forging of ni-base superalloys |
US5547523A (en) * | 1995-01-03 | 1996-08-20 | General Electric Company | Retained strain forging of ni-base superalloys |
FR2729675A1 (en) * | 1995-01-19 | 1996-07-26 | Turbomeca | Heat-resistant nickel@-based alloys |
US6059904A (en) * | 1995-04-27 | 2000-05-09 | General Electric Company | Isothermal and high retained strain forging of Ni-base superalloys |
US5649280A (en) * | 1996-01-02 | 1997-07-15 | General Electric Company | Method for controlling grain size in Ni-base superalloys |
US6068714A (en) * | 1996-01-18 | 2000-05-30 | Turbomeca | Process for making a heat resistant nickel-base polycrystalline superalloy forged part |
JP5278936B2 (en) * | 2004-12-02 | 2013-09-04 | 独立行政法人物質・材料研究機構 | Heat resistant superalloy |
US7763129B2 (en) * | 2006-04-18 | 2010-07-27 | General Electric Company | Method of controlling final grain size in supersolvus heat treated nickel-base superalloys and articles formed thereby |
US20090000706A1 (en) * | 2007-06-28 | 2009-01-01 | General Electric Company | Method of controlling and refining final grain size in supersolvus heat treated nickel-base superalloys |
FR2949234B1 (en) * | 2009-08-20 | 2011-09-09 | Aubert & Duval Sa | SUPERALLIAGE NICKEL BASE AND PIECES REALIZED IN THIS SUPALLIATION |
US9765416B2 (en) * | 2015-06-24 | 2017-09-19 | Ati Properties Llc | Alloy melting and refining method |
JP7375489B2 (en) * | 2019-11-20 | 2023-11-08 | 大同特殊鋼株式会社 | Manufacturing method of Ni-based heat-resistant alloy material |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US3667938A (en) * | 1970-05-05 | 1972-06-06 | Special Metals Corp | Nickel base alloy |
AU507373B2 (en) * | 1975-07-18 | 1980-02-14 | Special Metals Corp. | Heat Resistant Wrought Gamma Prime (ni+co+cr)base Superalloy |
US4083734A (en) * | 1975-07-18 | 1978-04-11 | Special Metals Corporation | Nickel base alloy |
CH654593A5 (en) * | 1983-09-28 | 1986-02-28 | Bbc Brown Boveri & Cie | METHOD FOR PRODUCING A FINE-GRAIN WORKPIECE FROM A NICKEL-BASED SUPER ALLOY. |
US4574015A (en) * | 1983-12-27 | 1986-03-04 | United Technologies Corporation | Nickle base superalloy articles and method for making |
US4579602A (en) * | 1983-12-27 | 1986-04-01 | United Technologies Corporation | Forging process for superalloys |
JPS6362584A (en) * | 1986-09-01 | 1988-03-18 | セイレイ工業株式会社 | Disk rotation type cereal grain selector |
US4820353A (en) * | 1986-09-15 | 1989-04-11 | General Electric Company | Method of forming fatigue crack resistant nickel base superalloys and product formed |
-
1992
- 1992-04-15 DE DE69218089T patent/DE69218089T2/en not_active Expired - Fee Related
- 1992-04-15 EP EP92911977A patent/EP0533914B1/en not_active Expired - Lifetime
- 1992-04-15 KR KR1019920703226A patent/KR100187794B1/en not_active IP Right Cessation
- 1992-04-15 JP JP04511740A patent/JP3073525B2/en not_active Expired - Fee Related
- 1992-04-15 WO PCT/US1992/003082 patent/WO1992018659A1/en active IP Right Grant
Also Published As
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JPH05508193A (en) | 1993-11-18 |
KR100187794B1 (en) | 1999-06-01 |
JP3073525B2 (en) | 2000-08-07 |
WO1992018659A1 (en) | 1992-10-29 |
DE69218089T2 (en) | 1997-06-19 |
DE69218089D1 (en) | 1997-04-17 |
KR930700231A (en) | 1993-03-13 |
EP0533914A1 (en) | 1993-03-31 |
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