US3331715A - Damping alloys and members prepared therefrom - Google Patents

Description

July 18, 1967 J, B i ET AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM Filed Oct. 16, 1959 V 9 Sheets-Sheet 1 Ag'ed 2500 Hour .IO o1 I2OQ F.

Fig. l E K E .06 Q) Q 0 .04- Aged l6 Hours .1

B of I200 F. .02 V 2 l o 1 I l l I 2 4 6 8 IO I2 l4 l6 Maximum Shear Stress (PSI. X I0 LcmeHor Colony Depleted Matrix and Strips of Precipitote Undeplefed Mofrix Zirconium- Rich 1". Second Phase Precipirote N WITNESSES INVENTORS Z I John Bulincl 8 Jack T. Brown July 18, 1967 J BUUNA ET AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM 9 Sheets-Sheet :1

Filed Oct. 16, 1959 Fig.3.

' Fig.4.

m u n e d b N M Voids 3 Molybdenum m U n e d b V. 0 M o c 4 Fig.5.

July 18, 1967 Log Decrement Log Decrement J. BULINA E AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM 9 Sheets-Sheet 3 Fig.6.

Room Tempe rafure 1% Molybdenum Fig.7.

Room Temperature v 2% Molybdenum July 18. 1967 DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM Filed Oct. 16, 1959 Log Decrement J. BULINA ET AL 3,331,715

9 Sheets-Sheet 4 Fig.8.

3% Molybdenum l I 1 IO 2O 25 30 Maximum Shear Stress- I000 PSI.

Room Temperature Fig.9.

- 4% Molybdenum l 5 IO I5 Maximum Shear Stress I000 PSI.

July 18, 1967 J. BULINA ET AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM 9 Sheets-Sheet Filed Oct. 16, 1959 n m w m g n .l u F T 2 e r U f. O r e D. m e T m 0 O R 6 5 3 2 m 0 O O O w EmZun o3 Room Temperature Molybdenum I Tu ngsten wEEumo o3 Maximum Shear Stress IOOO PSI.

July 18, 1967 BU A ET AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM Filed Oct. 16, 1959 9 Sheets-Sheet 6 /W'I W I! Low-Carbon 4 Mortensitic Matrix Maximum Shear Stress-I000 PSI.

July 1'8, 1967 J BULINA ET AL 3,331,715

DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM Filed Oct. 16, 1959 9 Sheets-Sheet '7 1 J. BULINA ETAL 3,331,715

DAHPING ALLOYS AND EEMBERS PREPARED THEREFROH 9 Sheets-Sheet 8 Filed (kit. 16, 1959 Fig. I?

July 18, 1967 BUUNA ET AL DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM 9 Sheets-Sheet 9 Filed Oct. 16, I959 Fig.l9

United States Patent 3,331,715 DAMPING ALLOYS AND MEMBERS PREPARED THEREFROM John Bulina, Greensbnrg, and Jack T. Brown, Monroeville, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 16, 1959, Ser. No. 846,906 11 Claims. (Cl. 148142) This invention is directed to a high damping alloy suitable for use over a wide range of temperatures and members prepared therefrom.

The problems associated with vibration and its reduction are becoming increasingly important as the demands made on modern machinery and materials increase. For example, in the fields of rotating and reciprocating machinery, the suppression of vibration is necessary for the prevention or drastic reduction of fatigue failure of machine elements stemming from vibration. Members which must be designed to resist fatigue failure could undoubtedly be made much lighter if vibration could be suppressed. Another benefit which would accrue from controlled vibration would be the reduction of noise which reaches objectionable levels in the larger apparatus.

In the past, in attempts to reduce the deleterious effects of vibration on members, there have been developed various mechanical devices for attachment to the members subject to vibration for vibration control. Satisfactory mechanical damping devices have not been developed for all applications, and at any rate, even in those cases where they are generally successful in reducing vibration, additional weight, bulk, and expense is involved in providing such damping devices.

A solution much more satisfactory than mechanical damping members is the provision of materials having inherent damping properties, and which have the other physical properties required by the member which is to be subjected to vibration. It is with this concept of providing high inherent damping properties in metals that this invention is concerned.

One of the critical problems in building turbines that must operate satisfactorily with inlet steam temperatures of from 1000 F. to 1200 F. has been the lack of alloys that have both high damping properties and high strength ductility .at such steam temperatures. These problems are even more severe when turbine operation at proposed temperature levels of up to 1300 F. are considered. In particular, the first rows of blades upon which the high temperature steam impinges are subjected to extreme vibration and shock, especially in turbines operating at partial steam admission, This may cause rapid fatigue of the blades unless adequately self-damping materials are employed for the blades.

Another critical problem which faces the designers of steam turbines is obtaining a material suitable for use in the manufacture of large, low temperature blades. The blades now being produced are as long as 25 inches, while the designs for future machines contemplate blades of almost twice that length. It is readily seen that blades of such extreme length present serious vibration problems.

On rare occasions, metallurgists have observed in photomicrographs small areas having a structure known as cellular precipitate. This cellular precipitate structure has been regularly regarded as being nndesirabel and efforts have been made to suppress it. Accordingly, no alloy having any significant amount of cellular precipitate has been produced or employed commercially. Further, there has been no understanding of What metallurgical phenomena gave rise to the formation of the cellular precipitate. According to the present invention it has been discovered how to produce certain alloys with relatively large amounts of the cellular precipitate. More importantly, contrary to the prior art knowledge, it has been found that shaped and hardened members of certain alloys having substantial amounts of cellular precipitate possess not only excellent physical properties, but are further characterized by outstanding high temperature damping properties.

The cellular precipitate comprises a plurality of lamellar colonies which consist of areas of relatively depleted matrix continuous with itself and the alloy matrix proper, and spaced strips of precipitate disposed in the depleted matrix. The spaced strips of precipitate in the depleted matrix resemble the pearlite structure in iron alloys. It is clearly observed in certain alloy sections etched with Fryes etch or electrolytically etched in a 10% chromic acid solution at a magnification of 5 00X One of the best available alloys for steam turbine blading presently employed is a 12% chromium-iron alloy corresponding to A181 403. This alloy, however, cannot be safely employed above 1050 F. and ordinarily its practical operating temperature limit is approximately 1000 F. The creep-rupture strength of this widely used alloy is relatively poor above 1000 F.

Recent efforts to provide alloys having good inherent damping properties are embodied in US. Patent No. 2,829,048, issued April 1, 1958, to A. W. Cochardt et al., entitled, High Damping Alloy and Members Prepared Therefrom, and in US. application Serial No. 721,275,

filed March 13, 1958, by A. W. Cochardt et al., entitled, High Damping High Temperature Alloy, now abancloned. The alloys disclosed therein posess a combination of damping properties and good mechanical properties at elevated temperatures unequaled in the prior art.

In determining the relative damping characteristics of the alloy of this invention, the vibration tests described in the following publication were employed: Foppl- Pertz Damping Machines, Metals and Alloys, New Products Section, February 1931, page 28.

The logarithmic decrement, as generally defined, was determined for the alloys at various vibratory surface shear strain values.

The primary object of this invention is to provide an alloy having high damping characteristics, the alloy comprising essentially predetermined critical amounts of nickel and at least one element selected from the group consisting of chromium, iron, and cobalt, and hardening constituents, the alloy structurally comprising a matrix with a substantial proportion of lamellar colonies distributed therein.

Another object of this invention is to provide a process for preparing high damping structural members from a hardenable alloy, the alloy containing as its essential components critical amounts of nickel and at least one element selected from the group consisting of chromium, iron and cobalt, and hardening constituents, the process developing in the alloy a structure comprising a matrix and a high proportion of lamellar colonies distributed therein.

It is a further object of this invention to provide members prepared from an alloy which is hardenable, the alloy base including predetermined amounts of nickel and at least one element selected from the group consisting of chromium, iron, and cobalt, and hardening constituents, wherein the alloy structurally comprises from 3% to by area as measured at any cross section of the member of lamellar colonies or cellular precipitate.

Still another object of this invention is to provide a precipitation hardenable cobalt-nickel base alloy having high damping properties, the alloy structurally consisting of lamellar colonies or a cellular precipitate in the cobaltnickel matrix.

7 It is still another object of this invention to provide a precipitation hardenable ferrous base alloy having excelle'nt damping properties, the alloy comprising predetermined critical amounts of iron, a proportion of nickel, and two or more elements selected from the group consisting of chromium, cobalt, titanium, copper and manganese, in which lamellar colonies or a cellular precipitate are distributed in an essentially ferrous matrix.

Other objects of the invention will, in part, be obvious and, in part, will appear hereinafter.

For a better understanding of the nature and objects of the invention, reference should be made to the following detailed description and drawings, in which: 3

FIGURE 1 is a graph plotting damping in terms of the logarithmic decrement against maximum surface shear stress at 1200 F. for two alloy structures;

FIGS. 2 through 5 are idealized representations of the microstructures of certain of the alloys of this invention;

FIGS. 6 through 11 are graphs of damping capacity similar to FIG. 1, for various of the alloys of this invention;'

FIGS. 12 and 13 are idealized representations of the microstructures of an alloy consistuting another embodiment of this invention;

- FIG. 14 is a graph of the damping capacities of the alloys of FIGS. 12 and 13; and

FIGS. 15 through 20 are actual photomicrographs of the alloys for which idealized representations are precipitate distributed in a matrix of the alloy which was described in detail hereinbefore. The lamellar colonies are similar to pearlite in appearance. By proper selection of the alloy constituents, the alloys will have, in addition to high damping properties, high creep rupture strength at temperatures of the order of 1200 F. and higher, and also reasonably high ductility at such elevated temperatures.

Broadly, the alloys of the present invention'include at least 3% of the element nickel and at least one element selected from the group consisting of chromium, iron, and cobalt, the total of nickel and these elements being at least 80%, and at least one additional precipitation V hardening constituent such as titanium, aluminum, copper and beryllium. In addition, there may be present other alloying components" such as molybdenum and tungsten and other additives and impurities. The worked and hardened alloy when suitably heat-treated as will be described herein, is particularly characterized by a microstructure imparting high damping properties, which microstructure consists of lamellar colonies orcellular precipitate distributed in a matrix, the lamellar colonies .constituting from 3% to 95% and, in some cases, all of the observable area of the alloy as measured at'any cross section.

The desired cellular precipitate microstructure is obtained by a heat treatment involving a solid solution treatment for from /2 to 4 hours at a temperature of from 1700 F. to 2000 F. followed by an aging treatment for from /2 to 2500 hours at a temperature of 1100 F. to '1650" F. The cellular precipitate microstructure may be developed concurrently 'with hardening of the alloy members or subsequently thereto.

More particularly; a series of cobalt-nickel base alloys incorporating the present invention have been prepared comprising, by weight, from 65% to 88% cobalt, at least 8% nickel, the cobalt and nickel totaling at least 90%, up to 4% titanium, up to 1.5% aluminum, up to 1% beryllium which can replace the titanium and the 1%. The alloys of this particular composition develop a cellular structure comprising lamellar colonies including titanium or beryllium-rich strips of precipitate distributed in an essentially cobalt-nickel matrix when solution treated for from /2 to 4 hours at a temperature from 1700 F. to 2000 F. followed by aging from about 200' to 2500 hours at a temperature of from 1100 F. to

from 94% to 96%, from .1% to 2% zirconium equivalent of at least one element selected from the group consisting of zirconium and hafnium, the Weight of hafnium being divided by 2 in calculating the effective zirconium equivalent, from 1% to 3% titanium, from 0.1% to 1.5% of aluminum, the total of titanium and aluminum not exceeding 3.5%, with the balance incidental impurities.

Good results have also been obtained employing ferrous-base alloys in which iron comprises from 50% to 80%, nickel from 3% to 12%, up to 18% chromium, up to 35% cobalt, and a precipitation hardening element selected from the group consisting of titanium and copper, titanium, when present, amounting to from 1% to 4% and copper, when present, amounting to from 3% to 5%, up to 3% manganese, up to 2% silicon, and up to 2 columbium. Members of the ferrous base alloy when solution treated for from /2 to 4 hours at a temperature of from 1700'F. to 2000 F., and aged for from /2 to 2500 hours at a temperature of from 1100 F. to 1650 F. develop a structure comprising lamellar colonies or a cellular precipitate distributed in a matrix, the lamellar colonies comprising from 3% to 95% by area as meas-. ured at any cross section of the alloy.

FIGS. 2 and 15 show an alloy having good damping properties and should be considered together, for FIG. 2 is an idealized representation of the microstructure of the alloy. shown in the photomicrograph of FIG. 15. These aluminum or it can be employed in combination with them, up to 5% molybdenum, up to 3% zirconium, carbon not exceeding .05%, with impurities not exceeding figures show a typical cobalt-nickel alloy of this invention after appropriate heat treatment and an electrolytic polish in a 10% chromic acid solution. The bulk of the alloy area as shown is occupied by the matrix, which appears as an extensive grey-colored area in the photomicrograph. Randomly dispersed in the matrix are numerous small black particles constituting the precipitate formed in the initial aging period. It is this precipitate Which confers increased hardness on the alloy. The irregular uniformly white bodies'in the figures are zirconium-rich second phase particles. Along the grain boundaries of the matrix lamellar colonies or cellular precipitate can be clearly seen. The black strips within the the precipitate. This precipitate is titaniumor beryllium-, rich, as the case may be. The alloy material lying between the precipitate lamellae and forming the alternate lamellae. is a matrix-like alloy which is depleted with respect to titanium or beryllium as compared with the matrix itself.-

In alloys whichare heat treated to reach an advanced stage of aging, the lamellar colonies progress'in their growth to a point where many of the separate colonies; v lose their individuality, and the lamellar colonies may occupyfrom upwards of'one-half to substantially all of the observed field. A structure having this amount of cellular precipitate is one which possesses outstanding high damping properties.

In alloys made in accordance with this invention for high temperature employment, the required high temperature properties are obtained in part by precipitation hardening formed and shaped members of the alloys by applying suitable aging treatment. Titanium in an amount ranging up to 4%, up to 1.5% aluminum, up to 1% beryllium, and up to 5% copper, are the constituents which are particularly used in various of the alloys to produce the desired hardness through precipitation phenomena.

Molybdenum and/ or tungsten may be present in the alloy in amounts up to 5% as a solid solution hardener. Columbium and tantalum may also be used for this purpose, the total amount of these latter elements not exceeding 1.5%.

In alloys intended for service at elevated temperature, zirconium may be present in amounts up to 2%, in order to improve the stress-rupture ductility in the alloy. Hafnium may replace all or a part of the zirconium, however, the weight of the hafnium should be twice the amount of zirconium replaced. Expressed in terms of zirconium equivalent, then, the weight of hafnium is divided by 2, since hafnium is one-half as effective as zirconium in improving the stress-rupture ductility.

Chromium may also be present in certain of the alloys in amounts up to as much as 30% to impart improved corrosion resistance.

In the cobalt-nickel base alloys, boron has been found to be detrimental when present in amounts exceeding about 0.002%, since it appears to inhibit or prevent the development of the cellular precipitate. Other elements which may be present in the alloy are silicon, manganese, and carbon as minor additives, and impurities such as sulfur, phosphorus, nitrogen, and oxygen.

In the preparation of the alloys of this invention, both vacuum melting and air melting techniques have been used with satisfactory results. The molten alloy may be cast directly into members of desired shape by precision casting or shell molding techniques. For most applications, however, it is desirable to cast an ingot of the alloy, which is then subjected to suitable forging or rolling or other working treatment to refine the grain structure and to produce homogeneous forgings, wrought members, or bar stock. The ingots may be heated to a temperature in the range from 1800 to 2200 F. and hot rolled or forged to shape with suitable heating if necessary.

Castings or wrought alloy members of the order of an inch or so in thickness are solution heat treated, ordinarily at temperatures in the range of from 1700 F. to 2000 F., for a period of approximately an hour. A half hour at temperature may be added for every additional inch of thickness. Thereafter, the solution heat treated member is aged at a temperature from approximately 1100 F. to 1650 F., and preferably, for some alloys, at about 1200 F., for a period of from /2 to 2500 hours. On very thin sections the aging time may be reduced to fifteen minutes or even less. The hardening of the alloy during this aging treatment occurs during the initial portion of the aging period. Thereafter, the additional aging is required to form the cellular precipitate which is essential to confer the excellent damping properties upon this alloy. It is an important characteristic of the alloys of this invention that the hardness acquired by aging is not materially affected by prolonged overaging. Thus, for example, the hardness of cobalt-nickel alloys aged for 2500 hours is not materially different from that of such alloys aged for a period at little as 16 hours at 1200 F.

The following examples are illustrative of the practice of the present invention.

EXAMPLE I nese .45%, carbon .01%, titanium 1.87%, aluminum .26%, zirconium 1.09%, iron 23%, silicon .2l%, phosphorus .008%, and sulfur .0l%. The zirconium addition was commercial grade containing about 2% hafnium therein. The ingot was fabricated to a 4.5 inch square billet by hammer and press forging at a temperature of from 2000 F. to 2100 F. Thereafter, the billets were rolled into inch square bars. The bars were solution treated at 1900 F. for one hour. Thereafter, one of the bars was aged at 1200 F. for 2500 hours. When etched cross sections of the bar were examined under the micro scope, it was observed that from 10% to 30% of the area under observation was occupied by lamellar colonies forming a cellular precipitate. In FIG. 1, in which damping in terms of the log decrement is plotted against maximum sheer stress, the extremely good damping properties of the alloy treated as described are shown in curve A.

In this same FIG. 1, by way of contrast, is plotted curve B of the damping characteristics of another sample in every respect similar to that of the first sample of the alloy except that this sample was aged at 1200 F. for only 16 hours. It will be noted that in the range from 6,000 to 14,000 psi. shear stress, the stress range which is of particular interest for high temperature steam turbine blades, the damping capacity of the first sample is from 2 to 7 times better than the damping capacity of the second alloy. When observed under the microscope the second sample contained no observable cellular precipitate.

EXAMPLE II The alloy in this example was of the same composition as that of Example I, and it was fabricated into bars in the same manner as Example I. The bars were then solution treated at a temperature of 17.50" F. for 1 hour. The solution treatment was followed by an aging treatment at 1200" F. for 1300 hours. Specimens treated with this lower solution temperature had a high proportion of cellular precipitate, from 10% to 30% of the area, and retained all the desirable mechanical properties, as well as a high damping capacity corresponding to the specimen of Example I.

EXAMPLE III A series of specimens was prepared having the same composition as the specimens of Example I except that the element molybdenum was added in a different amount to each one. Specimens having 1%, 2%, 3%, and 4% molybdenum were prepared. Fabrication of bars from the ingot was carried out as indicated in Example I. The bars were solution treated at 1900" F. for 1 hour. Each of the bars was then aged at 1200 F. for 500 hours. The specimens were examined under the microscope with the result that the 1% molybdenum-containing specimen was found to have 3% by area of lamellar colonies, the specimen containing 2% molybdenum had 20% by area of lamellar colonies, that containing 3% molybdenum had 30% by area of lamellar colonies, and the specimen containing 4% molybdenum had between 50% and 60% by area of lamellar colonies.

The microstructures of the alloys having 1%, 3%, and 4% molybdenum are shown in idealized representation in FIGS. 3 to 5 in order to emphasize the novel microstructure characteristic of the alloys of this invention. FIGS. 16 to 18 are photomigrographs showing actual structures corresponding to FIGS. 3 to 5, respectively. The lamellar colonies which are clearly indicated in FIGS. 3 to 5, appear as dark, somewhat poorly resolved masses in FIGS. 16 to 18. The solid black areas are voids created by removal of a second phase during etching and polishing. It will'be observed in FIGS. 5 to 18 (4% molybdenum) that the original grain boundaries are illdefined and the cellular precipitate has become the dominant structural feature of the alloy.

The damping properties of this last series of alloys is closely related to the area of lamellar colonie present, and hence to the amount of molybdenum, in the alloy.

7 ing capacities.

I In this connection, FiGS. 6-9 show the damping capacity of the series of alloys containing 1%, 2%, 3%, and 4% molybdenum. In the range from 6,000 to 14,000 p.s.i. shear stress, the damping capacity at elevated temperatures is strikingly improved as the amount of molybdenum increases. Comparison of the curves for 1200 F. damping reveals that while the damping capacity of the 1% and 2% molybdenum alloys ranges from a log decrement of .02 to .03 over the stress range of interest with the 2% molybdenum alloy considerably better than the 1% molybdenum alloy, the damping capacity of the 3% molybdenum alloy covers the range from .028 to .048,

3 and the damping capacity of the 4% molybdenum alloy 7 cipitate promoter of great potency and is highly desirable in amounts of from 1% to 5%.

The question naturally arises as to whether tungsten maybe substituted for all or part of the molybdenum in the alloys of this invention. Both molybdenum and tungsten are solid solution hardeners, and since the function of hardening is an important aspect of the molybdenum addition, tungsten may be substituted for the molybdenum to the extent that solid solution bardening is the desired result.

Tugsten is not, however, a promoter of cellular precipitate in the alloys of this invention. This is shown in FIGS. and 1 1 which are damping curves for a first alloy containing 2% tungsten, and another alloy containing 1% molybdenum and 1% tungsten; The 2% tungsten alloy has a generally lower damping capacity than the 1% molybdenum alloy (FIG. 6). The 1% molybdenum-1% tungsten alloy does not quite have the damping capacity of the 1% molybdenum alloy. It is clear,

therefore, that no beneficial effect on the damping capacity of the alloy may be expected from additions of tungsten.

Example IV An alloy falling in the following composition range was cast, forged, and fabricated to bar-stock.

The specimen bars were solution treated at 1900 F. for 1 hour and then quenched in oil. The aging treatment which followed involved heating the specimen bars to a temperature of 1400 F. for'a period of one hour.

When examined under a microscope, the ferrous-base alloy of this example exhibited from 80% to 95% of the observed area occupied by lamellar colonies. It will be understood that the specimens containing lamellar colonies to this extent exhibited greatly improved damp- FIGS. 12 and 13 are idealized representations of the microstructure of the alloy of Example IV in two conditions of heat treatment, while FIGS. 19 and 20 are actual photomicrographs of this alloy'and correspond to FIGS. 12 and 13, respectively. FIGS. 12 and 19 show the microstructure of the alloy after solution treatment at 1900 F. for one hour followed by an oil quench. The

predominant structure visible is a low carbon martensite. The second phase present is delta ferrite which is inherent to the base composition and remains unchanged by heat treatment. 3

FIGS. 13 and 20 show the same alloy after the same solution heat treatment and quench, and an aging treatment at 1400 F. for one hour. The alloy structure consists of the matrix which appears relatively light, and the precipitate which appears darkerand is arranged in temperature, the specimen with the cellular precipitate has two to four times the damping capacity of the specimen with the normal structure. 1

The alloy of Example IV is a moderately priced material being about as expensive as the materials of low damping capacity presently used for the low temperature exhaust'blades of steam turbines. For that reason, the

discovery that a high damping capacity structure can be developed in the alloy is extremely important. A superior product without substantial increase in cost is thus made available to the art.

The four examples given above indicate that cellular precipitate which is capable of imparting high damping capacity can be made to appear in alloys of widely vary- 9 ing composition. Thus, the damping capacities of cobaltnickel base alloys and of ferrous-base alloys can be improved. Further, the aging treatment which develops the desired structure in the alloy may be varied both as to temperature and time within limits to produce the structure.

Another alloy in which a substantial proportion of cellular precipitate may be' obtained by aging treatment,

and which thus may have its damping capacity substantially improved, comprises 30% cobalt, 10% nickel,'3%

titanium, and the balance approximately 55% iron with small amounts of additives and incidental impurities.

While considerable emphasis has been placed in this discussion upon alloys useful at elevated temperatures of say, 1200 F. and up, it should be understood that many low temperature applications are available for high damping capacity alloys. One such application is found in the exhaust blades in steam turbines which generally operate in the temperature range between F. and 450 F. Materials of the type disclosed herein might also be used in marine turbines which are frequently subjected to rather severe vibrational stresses due to the variable speed of these machines. These alloys can also be used to fabricate tool holders for lathes and drill presses, as a gear material, and for springs in certain vehicles.

Although the present invention has been described with reference to preferred embodiments, it will be ap.

parent to those skilled in the art that variationsand modifications may be made without departing from the essenone element selected from the group consisting of chromium, iron, and cobalt, chromium, when present, not

exceeding 30%, these components totaling at least and also contaming at least one precipitation hardening 3 constituent in eifective amounts up to 5%, and the balance bemg small amounts of additives and impurities,

the alloy microstructurally characterized by a matrix having lamellar colonies forming a cellular precipitate distributed therein, the lamellar colonies constituting at least 3% of any cross section of the alloy.

2. In a process for producing a heat-treated alloy having excellent damping capacity at elevated temperatures under stress, the alloy comprising as its essential components, of at least 3% and not in excess of 25%, by weight, of nickel and at least one element selected from the group consisting of chromium, iron, and cobalt, chromium, when present, not exceeding 30%, these components totaling at least 80%, and also containing at least one precipitation hardening constituent in effective amounts up to selected from the group consisting of titanium, aluminum, beryllium, and copper, and effective amounts not in excess of 5% of at least one element of the group consisting of molybdenum and tungsten, and the balance being small amounts of additives and impurities, the steps comprising, solution treating the alloy for from /2 to 4 hours at a temperature of from 1700" F. to 2000 F., and aging the alloy for from /2 to 2500 hours at a temperature of 1100 F. to 1650 F. until the alloy is microstructurally characterized by a matrix and lamellar colonies forming a cellular precipitate distributed therein, the lamellar colonies constituting at least 3% of any cross section of the alloy.

3. A precipitation hardened cobalt-nickel base alloy member having good elevated temperature properties and outstanding damping capability, the alloy microstructurally characterized by lamellar colonies forming a cellular precipitate distributed in an essentially cobaltnickel matrix, the area occupied by the lamellar colonies constituting at least 3% of any cross section of the member, the amount of cobalt in the alloy being at least twice the amount of nickel therein, the cobalt and nickel totaling at least 90%, and at least one precipitation hardening component in an effective amount of up to 4% from the group consisting of titanium, aluminum and beryllium, the balance being small amounts of additives and impurities.

4. A precipitation hardened cobalt-nickel base alloy member having good elevated temperature properties and outstanding damping capability, the alloy microstructurally characterized by an essentially cobalt-nickel matrix in which lamellar colonies forming a cellular precipitate are distributed, the lamellar colonies constituting at least 3% of any cross section of the member, and the amount of cobalt in the alloy being at least twice the amount of nickel therein, precipitation hardening components in effective amounts up to 4%, the precipitation hardening components being selected from at least one of the group consisting of aluminum, titanium, and beryllium, at least one element from the group consisting of molybdenum and tungsten in an amount of up to 5 up to 3% zirconium, up to 2% silicon, up to 2% manganese, up to 2% chromium, and carbon not exceeding .05%, the balance not exceeding 1% comprising small amounts of impurities.

5. A heat-treated member comprising an alloy composed of from 65% to 88% cobalt, effective amounts of up to 4% of at least one precipitation hardening constituent selected from the group consisting of titanium, aluminum, and beryllium, up to 5% molybdenum, up to 3% zirconium, carbon not exceeding .05% and the balance, at least 8%, being nickel, with impurities not exceeding 1%, the alloy characterized by an essentially cobalt-nickel matrix with lamellar colonies forming a cellular precipitate distributed therein, the cellular precipitate comprising at least 3% of any cross section through the alloy, the alloy characterized in exhibiting exceptionally high damping properties.

6. In a process for producing a member comprising an alloy having exceptional damping properties composed of from 65% to 88% cobalt, precipitation hardening components in effective amounts of up to 4% selected from at least one of the group consisting of titanium,

aluminum, and beryllium, up to 5% molybdenum, up to 3% zirconium, carbon not exceeding .05%, and the balance, at least 8%, being nickel, with impurities not exceeding 1%, and boron not exceeding 0.002%, the steps comprising, solution treating the member for from /2 to 4 hours at a temperature of from 1700 F. to 2000 F., aging the member for :from 200 to 2500 hours at a temperature of 1100 F. to 1450 P. so that the alloy develops a structure characterized by lamellar colonies distributed in a matrix, the lamellar colonies including a cellular precipitate and comprising in area at least 3% of the alloy as measured at any cross section through the member.

7. In a process for producing a member comprising an alloy composed of, by weight, from 70% to 75% cobalt, 25% to 20% nickel, the total of cobalt and nickel being from 94% to 96%, a total of from .1% to 2% zirconium equivalent of at least one element selected from the group consisting of zirconium and hafnium, the weight of the hafnium present being divided by 2 in calculating the effective zirconium equivalent, from 1% to 3% titanium, from 0.1% to 1.5% of aluminum, the total of titanium and aluminum not exceeding 3.5%, and the balance being incidental impurities, the steps comprising solution treating the member for from /2 to 4 hours at a temperature of from 1700 F. to 2000" F., and then aging for from 200 to 2500 hours at a temperature of 1100 F. to 1450" F. until the alloy develops a structure characterized by lamellar colonies distributed in the alloy matrix, the lamellar colonies comprising from about 10% to 30% of the alloy as measured at any cross section through the member, the alloy characterized by exceptionally high damping properties.

8. A ferrous base alloy member having good properties at elevated temperatures and characterized by outstanding damping properties at elevated temperatures while stressed, the alloy microstructurally characterized by lamellar colonies distributed in an essentially ferrous matrix, the lamellar colonies forming a cellular precipitate and occupying from about 60% to 95% at any observed cross section of the member, the alloy comprising, by Weight, from 10% to 20 chromium, 3% to 5% nickel, an effective amount of up to 5% copper as a precipitation hardener, up to 1.5 columbium as a solid solution hardener, up to 1.5% manganese, up to 1.5% silicon, and up to .15% carbon, and the balance iron with small amounts of additives and incidental impurities.

9. A ferrous base alloy member having good properties at elevated temperatures and characterized by outstanding damping properties at elevated temperatures While stressed, the alloy microstructurally characterized by lamellar colonies distributed in an essentially ferrous matrix, the lamellar colonies occupying at least 3% of any observed cross section of the member, the alloy comprising up to 35% cobalt, 3% to 12% nickel, an eifective amount of up to 4% titanium as a precipitation hardener, and the balance, of at least 50%, iron, with incidental impurities.

10. A member suitable for use as a turbine blade comprising an alloy having exceptional damping properties composed of, by weight, from to 88% cobalt, precipitation hardening components in effective amounts of up to 4% selected from at least one of the group consisting of titanium, aluminum, and beryllium, up to 5% molybdenum, up to 3% zirconium, carbon not exceeding .05%, and the balance, at least 8%, being nickel, with impurities not exceeding 1% and boron not exceeding 0.002%, the alloy characterized by lamellar colonies distributed in a matrix, the lamellar colonies including a cellular precipitate and comprising in area at least 3% of the alloy as measured at any cross-section through the member.

11. A turbine blade comprising an alloy composed of, by weight, from to cobalt, 25% to 20% nickel,

1 1 the total of cobalt and nickel being from 94% to 96%, from 0.1% to 2% zirconium, from 1% to 3% titanium, from 0.1% to 1.5% of aluminum, the total of titanium and aluminum not exceeding 3.5%, and the balance being incidental impurities, the alloy structurally characterized by lamellar colonies distributed in the alloy matrix, the lamellar colonies comprising from about 10% to 30% of the alloy as measured at any cross-sec tion through the member whereby the member is distinguished by exceptionally high damping properties.

References Cited UNITED STATES PATENTS OTHER REFERENCES ASM. Educational Lectures on Precipitation from Solid'Solution, 1959, pages? 265-268. Published by the American Society for Metals, Cleveland, Ohio. 7

ASM. Educational Lectures on Precipitation from Solid Solution, 1959, pages 106, 279 to 287, 439 to 447 and 454 to 490. Published by the'American Society for Metals, Cleveland, Ohio. (Dates relied' on are the dates 'on which the lectures were delivered, Nov. 4-8, 1957.)

Entwhistle, Changes of Damping Capacity in Quick- Aging Al-Rich Alloys, Journal, Institute of Metals, vol. 82, 195354,pages 249, 26 3.

HYLAND BIZOT, Primary Examiner.

RAY K. WINDHAM, MARCUS U. LYONS, ROGER L. CAMPBELL,- DAVID L. RECK, Examiners.

R. N. WARDELL, M. A. CIOMEK, C. M. SCHUTZ- MAN, R. O. DEAN, Assistant Examiners.

Claims (1)

1. 2. IN A PROCESS FOR PRODUCING A HEAT-TREATED ALLOY HAVING EXCELLENT DAMPING CAPACITY OF ELEVATED TEMPERATURES UNDER STRESS, THE ALLOY COMPRISING AS ITS ESSENTIAL COMPONENTS, OF AT LEAST 3% AND NOT IN EXCESS OF 25%, BY WEIGHT, OF NICKEL AND AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, IRON, AND COBALT, CHROMIUM, WHEN PRESENT, NOT EXCEEDING 30%, THESE COMPONENTS TOTALING AT LEAST 80%, AND ALSO CONTAINING AT LEAST ONE PRECIPITATION HARDENING CONSTITUENT IN EFFECTIVE AMOUNTS UP TO 5% SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ALUMINUM, BERYLLIUM, AND COPPER, AND EFFECTIVE AMOUNTS NOT IN EXCESS OF 5% OF AT LEAST ONE ELEMENT OF THE GROUP CONSISTING OF MOLYBDENUM AND TUNGSTEN, AND THE BALANCE BEING SMALL AMOUNTS OF ADDITIVES AND IMPURITIES, THE STEPS COMPRISING, SOLUTION TREATING THE ALLOY FOR FROM 1/2 TO 4 HOURS AT A TEMPERATURE OF FROM 1700* F. TO 2000*F., AND AGING THE ALLOY FOR FROM 1/2 TO 2500 HOURS AT A TEMPERATURE OF 1100*F. TO 1650*F. UNTIL THE ALLOY IS MICROSTRUCTURALLY CHARACTERIZED BY A MATRIX AND LAMELLAR COLONIES FORMING A CELLULAR PRECIPITATE DISTRIBUTED THEREIN, THE LAMELLAR COLONIES CONSTITUTING AT LEAST 3% OF ANY CROSS SECTION OF THE ALLOY.

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