AU708992B2 - Hot corrosion resistant single crystal nickel-based superalloys - Google Patents

Description

HOT CORROSION RESISTANT SINGLE CRYSTAL NICKEL-BASED SUPERAITOYS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to single crystal nickel-based superalloys and, more particularly, single crystal nickel-based superalloys and articles made therefrom having increased resistance to bare hot corrosion for use in gas turbine engines.

2. Description of the Prior Art Advances over recent years in the metal temperature and stress capability of single crystal articles have been the result of the continuing development of single crystal superalloys, as well as improvements in casting processes and engine application technology. These single crystal superalloy articles include rotating and stationary turbine blades and vanes found in the hot sections of gas turbine engines. Gas turbine engine design goals have remained the same during the past decades. These goals include the desire to increase engine operating temperature, rotational speed, fuel efficiency, and engine cmponent durability and reliability.

Prior art attempts to provide alloys to help achieve these design goals for industrial gas turbine engine applications include U.S. Patent No.

4,677,035, Fiedler et al. which discloses a nickel-base single crystal alloy composition consisting essentially of, in percent by weight, 8.0-14.0% M4 Chromium, 1.5-6.0% cobalt, 0.5-2.0% molybdenum, 3.0-10.0% tunsten, 2.5-7.0% titanium, 2.5-7.0% aluminum, 3.0-6.0% tantalum, and the balance nickel.

However, the alloy compositions taught by this reference, while possessing relatively high strength at prolonged or repeated eqxosure to high teIperatures, are susceptible to the accelerated corrosive effect of the hot gas envirorment in whid camponents fabricated fro the alloys are exposed to whaen used in gas turbines.

Also, U.K. Patent Application Publication No. 2153848A discloses nickel-base alloys having a composition within the range of 13-15.6% chromium, 5-15% cobalt, 2.5-5% molybdenum, 3-6% tungsten, 4-6% titanium, 2-4% aluminum, 0: *0 and the balance essentially nickel without intentional additions of carbon, boron or zirconium, which are fabricated into single crystals. Although the 0 alloys taugt by this reference claim an iprovent in hot corrosion resistance acuanied by an increase in creep rupture properties, the need S remains in the art for single crystal superalloys for industrial gas turbine applications having a superior combination of increased hot corrosion resistance, oxidation resistance, mehanical strength, large ronent *Ot.

castability and adequate heat treatment response.

single crystal articles are generally produced having the lowmodulus (001) crystalloraphic orientation parallel to the capnent dendritic growth pattern or blade stacking axis. Face-centered cubic superalloy single crystals grown in the (001) diretion provide extremely good thermal fatigue resistance relative to conventionally cast polycrystalline articles.

Since these single crystal articles have no grain boundaries, alloy design without grain boundary strengtheners, such as carbon, boron and zirconium, is possible. As these elements are alloy melting point depressants, their essential elimination frm the alloy design provides a greater potential for high temperature mechanical strength achievement since more omplete gamma prime solution and microstructural hamogenization can be achieved relative to directionally solidified (DS) columnar grain and conventionally cast materials, made possible by a higher incipient melting temperature.

These process benefits are not necessarily realized unless a multi-faceted alloy design approach is undertaken. Alloys must be designed to avoid tendency for casting defect formation such as freckles, slivers, spurious grains and recrystallization, particularly when utilized for large cast carponents. Additionally, the alloys must provide an adequate heat treatment "window" (numeric difference between an alloy's gamma prime solvus and incipient melting point) to allow for nearly complete gamma prime solutioning. At the same time, the alloy compositional balance should be designed to provide an adequate blend of engineering properties necessary for operation in gas turbine engines. Selected properties generally considered iportant by gas turbine engine designers include: elevated temperature creep-rupture strength, thermo-mechanical fatigue resistance, impact resistance, hot corrosion and oxidation resistance, plus coating performance.

In particular, industrial turbine designers require unique blends of hot corrosion and oxidation resistance, plus good long-term mechanical properties.

An alloy designer can attempt to improve one or two of these design properties by adjusting the ccmpositional balance of known superalloys.

However, it is extremely difficult to improve more than cne or two of the design properties without significantly or even severely omprmising sane of the remaining properties. The unique superalloy of the present invention provides an excellent blend of the prqoperties necessary for use in producing single crystal articles for operation in industrial and marine gas turbine engine hot sections.

SUMMARY OF THE INVENTION This invention relates to a hot corrosion resistant nickel-based superalloy comprising the following elements in percent by weight: from about 14.2 to about 15.5 percent dchromium, frxn about 2.0 to about 4.0 percent cobalt, from about 0.30 to about 0.45 percent molybdenum, fram about 4.0 to about 5.0 percent tungsten, franom about 4.5 to about 5.8 percent tantalum, fraom about 0.05 to about 0.25 percent columbium, fram about 3.2 to about e* 3.6 percent aluminum, fran about 4.0 to about 4.4 percent titanium, fra aboutt oe...

0.01 to about 0.06 percent hafnium, and the balance nickel plus incidental impurities, the superalloy having a pbasial stability number NOB less than about 2.45.

Advantageously, the sum of aluminum plus titanium in this superalloy composition is fran 7.2 to 8.0 percent by weight. Also, it is advantageous to have a Ti:Al ratio greater than 1 and a Ta:W ratio greater than 1 in the composition of the present invention. Although incidental ipurities should be kept to the least amount possible, the superalloy can also be ccmprised of from about 0 to about 0.05 percent carbon, fram about 0 I k) to about 0.03 percent boron, frm about 0 to about 0.03 percent zirconium, fron about 0 to about 0.25 percent rhenium, from about 0 to about 0.10 percent silicon, and fran about 0 to about 0.10 percent manganese. In all cases, the base element is nickel. This invention provides a single crystal superalloy having an increased resistance to hot corrosion, an increased resistance to axidation, and increased creep-rupture strength.

Single crystal articles can be suitably made fram the superalloy of this invention. The article can be a ccmponent for a gas turbine engine and, more particularly, the corponent can be a gas turbine blade or gas turbine vane.

SThe superalloy carpositions of this invention have a critically balanced alloy chemistry which results in a unique blend of desirable properties, including an increased resistance to hot corrosion, which are particularly suitable for industrial and marine gas turbine applications.

These properties include: excellent bare hot corrosion resistance and creeprupture strength; good bare oxidation resistance; good single crystal component castability, particularly for large blade and vane couponents; good solution heat treatment response; adequate resistance to cast component recrystallization; adequate component coatability and microstructural stability, such as long-term resistance to the formation of undesirable, brittle phases called topologically close-packed (TCP) phases.

Accordingly, it is an object of the present to provide superalloy ositins and single crystal articles made theref having a uniqu compositions and single crystal articles made therefram having a unique blend of desirable prcperties, inclding increased hot corrosicn resistancxe. It is a further cbjeCt Of the Present Invention to Provide s1peralloys and single crystal articles made therefrom for us in industrial and marirm gas turbine engines. These and other objects and advantages of the present invention will be apparent to those skilled in the art t.pon reference to the following description of the preferred embodiments.

Eg DEIPI'ION OF TH MWANGS FIG. 1 is a chart of hot corrosion test results perfored at three :exposure temperatuires on one embodiment of this invention and on four other alloys.

FIG. 2 is a graphiical cctjarison of hot crrosion data fran tests .:performed at 732 0 C (1350 0 DF) on one enboimnt of this invention and on two other alloys.

FIG. 3 is a graphical ctparison of hot corrosion data frcm tests .*performed at 899 0 C (1650 0 F) on one emoimtent of this invention and on two other alloys.

FIG. 4 is a graphical caparison of alloy strength and hot corrosion data fran tests performed on one emboiment of this invention and on six other alloys.

Lk FIG. 5 is a grapical cczrpariscn of oxidation data fran tests performed at 1000 0 C (1832 0 F) on on emboimrent of this invention and on two other alloys.

FIG. 6 is a graphical comparison of oxidation data fza tests performed at 1010 0 C (18 50 0 F) on on emboiment of the present invention andi on two other alloys.

FIG. 7 is a graphical couparison of alloy strength and oxidation data from tests performed on one emboiment of this invention ard on six other alloys.

.4

S

invention DESCRI=rIC OF RFER EMBDIMER The hot corros ion resistant nlickel-based superalloy, of the present comprises the following elements in percent by wight: chromium about 14.2-15.5 Cbalt abouzt 2.0-4.0 Molybdenum about 0.30-0.45 Tu\rsten abou.t 4.0-5.0 Tantalum about 4.5-5.8 Clumbium abou~t 0.05-0.25 Aluminum abou.t 3.2-3.6 Titanium abou.t 4.0-4.*4 Hafnium about 0.01-0.06 Nickel Incidental balance Ilmprities, This superalloy ccuposition also has a phasial stability nu~mber N,,3 les than abouzt 2.45. Further, this invention has a critically balanced alloy chemistry which results in a unique blend of desirable prcpexties useful for industrial and marine gas turbine engine applications. Thiese prcperties include a superior blend of bar hot corrosion resistance and creep-ruture strexrth relative to prior art single crystal superalloys for industrial and marine gas tu~rbine applications, bare oxidation resistance, single crystal ocxiponent Castability, and microstnactural stability, including resistance to Tc phase formation under high stress, high temerature conditions.

Superalloy chroium content is a primary contribuitor toard :attaining superalloy hot corrosion resistance. The superalloys of the present invention have a relatively high chroium content since alloy hot corrosion resistance was one of the primary design criteria in the deve1c~rnt of these :alloys. The d-iraium is abot 14.2-15.5% by weight. Advantageously, the chromium~ content is fra 14.3% to 15.0% by weight. Athuh chromium provides hot corrosion resistance, it ray also assist with the alloys' oxidation capability. Additionally, this superalloys' tantalum and titanium contents, as well as its Ti:Al ratio being greater than 1, are beneficial for hot corrosion resistance attainment. However, besides lowering the alloys, gamma prim~ solvus, chrmnium contributes to the formation of Cr and W-rich TIC phase and jzst be balanced accrdingly in these =p~ositions.

In one embodime~nt of the present invention, the coalt content is about 2.0-4.0% by weight. In another embodiment of the present invention, the ccalt cotent is fra 2.5% to 3.5% by weight. The dramium and coalt levels in these superalloys assist in making the sqeraloy solution heat treatable, since both elements tend to decrease an alloy's gamm~a prime solvus. proper balancing of these elements in the present inention in tarn with thoe whichi tend to increase the alloy's incipient melting texrperature, sudh as btsten and~ tantalum, result in SUper-aloy a=usitiOns which have desirable solution heat treatmnt windows (rnmerical dIfference between an allocy's inipient melting Point and its garmi prim solvus), thereby facilitating full gamma prim solutioig. The cobalt content is also beneficial to the superal1loy's solid solubility.

The tungsen content is about 4.0-5.0% by weight and, advantageou.sly, the amou.nt of tugsten is from 4.2% to 4.8% by weight.

:..Tangsten is added in these cositions since it is an effective solid solution strengthener ard it can contribuite to strengthening the ganua prim.

Additionally, tungsten is effective in raising the alloy's incipient melting tenperature.

Similar to tungsten, tantalumn is a significant solid solution strengthener in these ccupsitions, while also contribuiting to enhaced gamma prime particle strength and volume fraction. The tantalumn con-tent is about 4.5-5.8% by weight andi, advantageously, the tantalum content is fra 4.8% to 5.4% by weight. In these =puositions, tantaltum is beneficial since it helps to Provide bare hot corrosion and oxidation resistance, along with altrninide coating durability. Additionally, tantalumn is an attractive single czysta.1 alloy additive in these cjitions since it assists in preventIng 1frcklel" defect formation during the single =ystal casting process particularly when present in greater proportion than txxgsten the Ta :W ratio is greater than Furthermore, tantalm is an attractive mzeans of strength attainment in these alloys since it is believed not to directly participate in 7r phase formationi.

The mlybdenUM axtent is aboult 0.30-0.45% by weight.

Mdvantagecisly, mlybenum~ is present in an amouznt of fran 0.35% to 0.43% by weight. Molybdenum is a good solid solution strengthener, but it is not as effective as tmx-jsten and tantalum, and it texis to be a negative factor 7toward hot corrosion capability. However, since the alloy's density is always design consideration, and the mly~ennn atom is lighter than the other :':solid solution strerGtheniers, the addition of mlybdenum is a means of *assisting control of the overall alloy density in the cctqsitins of this :::invention. It is believed that the relatively low mlybdenumn content is :unique in this classq of bare hot corrosion resistant nickel-based single cystalJ superallcys.

The aluminum content is about 3.2-3.6% by weight. Fsz-thenzre, .:the amount of aluminum present in these carpositions is advantageously fran 3.3% to 3.5% by weight. Aluminum and titanium are the primazy elements cmprisirxq the ganma prime gose, and the sum of aluminum plus ttanium in the Present inrvention is from 7.2 to 8.*0 percent by weight. These eljnents are added in the-se catuositions in a proportion and ratio consistent with achieving adequate alloy castabiity, solution heat treatability, ptasial stability aid the desired blend of high izechanical strength aid bat crrosion resistance. Aluminum is also added to these alloys in pro.portions sufficient to provide oxidation resistance.

he titanium content is about 4.0-4.4% by weight. Avantageously, titanium is present in this cposition in an amount frcm 4.1% to 4.3% by weight. These alloys' titanium content is relatively high and, therefore, is beneficial to the alloys' hot corrosion resistance. Hwever, it can also have a negative effect on oxidation resistance, alloy castability and alloy response to solution heat treatment. Accordingly, it is critical that the titanium content is maintained within the stated range of this composition and S the proper balancing of the aforementioned elemental constituents is maintained. Furthermore, maintaining the alloys' Ti:Al ratio greater than 1 is critical in achieving the desired bare hot corrosion resistance in these S cmnpositions.

The columbium content is about 0.05%-0.25% by weight and, advantageously, the columbium content is fram 0.05% to 0.12% by weight.

Columbium is a gamma prime forming element and it is an effective strengthener in the nickel-based superalloys of this invention. Generally, however, columbium is a detriment to alloy oxidation and hot corrosion properties, so its addition to the campositions of this invention is minimized. Moreover, columbium is added to this invention's campositions for the purpose of gettering carbon, which can be chemi-sorbed into coponent surfaces during non-ptimized vacuum solution heat treatment procedures. Any carbon pick-up will tend to form columbium carbide instead of titanium or tantalum carbide, thereby preserving the greatest prqportion of titanium and/or tantalum for gamma prime and/or solid solution strengthening in these alloys. Furthermore, it is critical that the sum of columbium plus hafnium is from 0.06 to 0.31 percent by weight in these compositions in order to enhance the strength of these superalloys.

The hafnium content is about 0.01%-0.06% by weight and, advantageously, hafnium is present in an amount from 0.02% to 0.05% by weight.

Hafnium is added in a small proportion to the present compositions in order to assist with coating performance and adherence. Hafnium generally partitions to the gamma prime phase.

The balance of this invention's superalloy compositions is comprised of nickel and small amounts of incidental impurities. Generally, these incidental impurities are entrained from the industrial process of production, and they should be kept to the least amount possible in the camposition so that they do not affect the advantageous aspects of the superalloy. For example, these incidental impurities may include up to about 0.05 percent carbon, up to about 0.03 percent boron, up to about 0.03 percent zirconium, up to about 0.25 percent rhenium, up to about 0.10 percent silicon, Sand up to about 0.10 percent manganese. Amounts of these impurities which exceed the stated amounts could have an adverse effect upon the resulting alloy's properties.

Not only does the superalloy of this invention have a composition within the above specified ranges, but it also has a phasial stability number N3g less than about 2.45. As can be appreciated by those skilled in the art, Nv3B is defined by the IWA N-35 method of nickel-based alloy electron vacancy TP phase control factor calclation. Tis calcalation is as follows: EXJTON 1 Oxversion for weight percent to atomic percent.

Atcmic percent of element i Pi XaOO ri (Wi/Ai0 where: Wi weight percent of element i Ai atomic weight of element i EcUrCON 2 Clculation for the arunt of each element present in the continuous matrix phase: Elmett Atnmic amount .ii rJA inir

S,

*5 S S Cr Ni Ti, Al, B, C, Ta, MD, Hf

V

W

R~r=0-97P-0.375P 8 -1.75PC RN±Pxi+.525P3(PI+O.OPC+PT-O.5PC+.5pV+PT+p~PHf) Ri=O RcW)=Pw O.167PC P-4 PMo +PW 75PB-0.167PC

(PMO+PW)

ri r r ci EOATI 3 Calculation of N.

3 using atonic factors from Equations 1 ar 2 above: i

N

1 R.

then N, 3 6 E 1 Ni(Nv)i where: i each irdividual element in turn.

N i the atomic factor of each element in matrix.

(Nv)i the electron vacancy No. of each respective element.

This calculation is exemplified in detail in a technical paper entitled "AMP Revisited", by H. J. Murphy, C. T. Sims and A. M. Beltran, published in Volume 1 of International Sympsium on Structural Stability in Superalloys (1968), the disclosure which is incorporated by reference herein. As can be appreciated by those skilled in the art, the phasial stability number for the superalloys of this invention is critical and nust be less than the stated maxmun to provide a stable microstructure and capability for the desired properties under high taemperature, high stress conditions. The phasial stability number can be determined empirically, once the practitioner skilled in the art is in possession of the present subject oo** matter.

The superalloys of this invention can be used to suitably make single crystal articles, such as carqxents for industrial and marine gas turbine engines. Preferably, these superalloys are utilized to make a single *o crystal casting to be used under high stress, high temperature conditions characterized by an increased resistance to hot corrosion (sulfidation) under such conditions, particularly high temperature corditions involving corrosive atmospheres containing sulfur, sodium and vanadium contaminants, up to about 1922 0 F (1050 0 While these superalloys can be used for any purpose requiring high strength castings produced as a single crystal, their particular use is in the casting of single crystal blades and vanes for industrial and marine gas turbine engines.

The single crystal caponents made fran this invention's ccqpsitions can be produced by any of the single crystal casting techniques kcn in the art. For emaizple, single crystal directiona solidification processes can be ut-ilized, such as the seed crystal process and~ the chioke process.

The single crystal castings made fran the s-zralcys of the Present invention can be aged at a ter~ature of from about 1800'F (982 0 C) to about 2125F (1163 0 C) for about 1 to about 50 hours. However, as can be aPreiated by those skilled in the art, the cptimm aging tznerature and tim for aging depends on the precise amposition of the superalloy.

Mhis invention Provides superalloy corpcsitions having~ a unique blend of desirable properties. These properties include: excellent bare hot 0 crrosion resistance and creep-rupture strength; good oxidation reistance; good single crystal caTionent castability, particularly for large blade and vane cczrponents; good solution heat treamnt response; adequate resistance to 0cast crca-ent recrystallization; adequate coaponent coatability and microstnicbara stability, sudih as long-term resistance to the formation of undesirable, brittle ph~ases called toologically close-packed (TCp) phases..

As noted above, this superalloy has a precise =rqosition with only mail permissible variations in any one elmmt if the unique blend of properties is to be maintained.

In order to more clearly illustrate this invention ard provide a ccrparison with representative superalloys outside the claied~ of the invention, the exazrles set forth below are presented. The folluding exwnples are includled as being illustrations of the invention and its relation to other superallcys and1 articles, and should not be construedi as limiting the sope thereof.

.Woo* *so* 0 4 4* 0 Test materials w~ee prepared to investigate the coaositiona1 variaticns and ranges for the s-;raloys of the presen-t invention. One of the alloy ampcsitins tested and reported below falls outside the cla.ined scope of the present inv~.ention, buzt is irc1ile for caarative purposes to Assist in the urerstanding of the invention. Representative alloy aim cheistries of mterials tested are reported in Table 1 below.

9S @0 9 0 0p0@@S 0 0 0 9 0* 0 9 9 @0 9

C!

Ti Hf Ni Nv3B T-ap 14.5 4.4 4.95 3.40 4.20 .04

BAL

2.41 Chemistries are TABLE I AIM CHEMISTRIES lap Lap 14.5 14.4 2.5 2.9 .35 .40 4.6 4.5 5.1 5.1 .08 .10 3.40 3.4 4.15 4.2 .03 .04 BAL BAL 2.40 2.42 C2X-123 lap 12.5 0.55 5.15 0.20 3.60 4.20 0.040

BAL

2.42 in wt. Test materials defined by the CMSX8-11C aim dchemistry shown in Table 1 were initially produced by mixing 15 Ibs. of the heat R2D2 alloy (see Table 2 below) with 8 lbs. of virgin materials, melting and subsequently pouring the melt into a ceramic shell mold. (CMSX is a registered trademark of Cannon-Muskegon Corporation, assignee of the present application).

Nineteen (19) each diameter x 6" long test bars plus three each solid turbine blades were investment cast with the resulting blended product. Specimen inspection revealed satisfactory grain yield with only one test bar rejectable for misorientation. No freckles were apparent. Furthermnore, a test-bar chemistry check indicated that the CMSX-11C aim composition was attained.

*foe*: I a a 0 a *a Further test materials were obtained with alloy product which was VIM produced in 250 -270 lb. (113-122 kg.) quantities. The VIM heats that were produced and their *9 p respective chemistries are reported in Table 2 below.

a a a

N'

S

S. 0 5 00 00 ~0 0 0* S 0 S S *0 0@

S*

5 00 0* S 0 S OS 0 00: 000 0 .S TABLE 2 VIM FURNACE HEAT CHEMISTRIES C Cr ODb M W Th C2 AIL Ti Hf Ni. N,3 Heat #/Allcy Designation jpp VF 952/R2D2 VF 998/OCLSX-l1C NUM': Chiemistries in wt.

10 11.0 4.9 .49 14 14.6 3.0 .41 11 14.4 3.0 .40 16 14.4 2.4 .35 12 14.6 2.4 .36 14.4 2.4 .35 14.4 2.9 .40 unless otherwise indlicated.

2.5 4.4 4.4 4.6 4.6 4.6 4.5 5.0 4.95 4.9 5.0 5.1 5.1 5.1 <.01 .10 .10 .07 .09 .08 .10 3.39 3.4 3.46 3.4 3.4 3.4 3.4 3.76 4.18 4.15 4.1 4.1 4.1 4.2 .05 .03 .03 .03 .04 .03 .04

BAL

BAL

BAL

BAL

BAL

1.92 2.42 2.41 2.37 2.41 2.38 2.42 Small quantities of these materials were re-melted and precision investment cast into both bar and blade configurations.

Grain and orientation inspections for product that was investment cast yielded satisfactory results. Generally, the aim compositions reported in Table 1 above, resulting in product reported in Table 2, yielded SX cast parts which were single crystal, void of spurious grain and/or sliver indications, free of apparent freckles, possessed orientations generally within 10° of the desired primary (001) crystallographic orientation, and met the caompositional requirements.

0. Sae of the test specimens produced were used to develop appropriate solution heat S treatment procedures, with the results reported in Table 3 below. Cmplete coarse 0. y' and eutectic y-Y' solutioning was achieved with a peak solution temperature of *g 0. 2309 F (1265*C) applied. But variable levels of test specimen recrystallization, occurring during solution heat treatment, was observed. This problem was alleviated by reducing the CMX-11C alloy peak solution temperature to 2289F (1254*C), where Sfull Y' solutioning still prevailed.

0oo* Similarly, the other two compositional variants listed in Table 1 (CMX-llC' and CMX-11C") were solution treated to a peak temperature of 2289F (1254°C) with similar results.

All test specimens were further heat treated by aging initially at 2050F (1121°C) to encourage a desirable y' morphology and distribution, followed by secondary ages at 1600"F (871°C) and 1400°F (760*C), respectively (see Table 3 below).

'A

TABLE 3 HEAT TREATMENT DP ALlOY oMSX-11c 2309 (1265) 2050-F/5 Hrs/AC 1600'F/24 HrS/AC 1400 'F/30 Hrs/AC p 9* p and *2289 (1254) 2050 'F/5 Hrs/AC 1600-'F/24 Hrs/AC 1400-F/30 Hrs/AC CKSx-11cI andii' 2289 (1254) 2050 'F/5 Ers/AC 1600'F/24 HrS/AC 1400'F/30 Hrs/AC NOM1: Lader solution tenerature choen to reducea tendency taard sx cast product recystallization during solution heat treatmnt.

Differential Thennal Analysis (DMA) of the VIM! heats (reported in Table 2 above) produced respective alloy solidus and liquidus data. Thie Dnk detail is reported in Table 4 below.

HEAT

VF 998 VG 33 VG 110 VG 113 VG 148 VG 175 TABLE 4 DTA DATA

SOL=U

*F 2296 (1258) 2298 (1259) 2305 (1263) 2300 (1260) 2302 (1261) 2306 (1263) F V'Q 2404 (1318) 2403 (1317) 2408 (1320) 2402 (1317) 2414 (1323) 2412 (1322) E 9 9 *9 99 9 9 9 4 9 .9.99.

Following heat treatment, test bars were machined and low-stress ground to ASIM standard proportional specimen dimension for subsequent stress and creep-rupture testing at various conditions of temperature and stress, according to standard ASIM procedure. Specimens rerved from solid turbine blades were prepared similarly.

Table 5 below shows the results of stress and creep-rupture tests undertaken with the CMSX-11C alloy specimens. The tests were performed at conditions ranging 1400- 1900"F (760-1038"C).

Most of the tests reported in Table 5 were undertaken with alloy originating from the previously detailed heat R2D2/virgin material blending along with product from heat VF 998. Test results for materials produced with heat VG 33 product are highlighted in Table 5. No rupture tests were performed with product originating from the remaining VIM heqts listed in Table 2 above.

MU3E AND CREEP-R p'rURL flATA STRESS CMSX-11C Alloy TETCr aT 1400 F/95.0 kSi (760 C/655 Ma) 681.8 627.6 677.4 220.9 4+ 321.6 418.*4 317.7 10.8 14.*3 14.4 5.5 5.5 8.9 11.3 16.*7 17.8 17.*8 7.8 10.7 17.0 P32AL CREP IMr 681.1 10.331 56.6 215.8S 417.1 316.5 7.842 10. 405 100.8 97.8 232.6 182.2 /50-0 ksi (871 C/345 Ma) 1600 P/55. 0 ksi (871:C/379 MPa) 2650.F/45.0 ksi (899 C/310 MPa) 977.1 294.7 621.3 314.3 4+ 366.4 251.6 228.6 461.8 9.2 10.6 15.9 8.4 5.5 7.4 9.2 9.0 13.1 12.5 16.*2 9.2 9.2 10.8 18.0 13.4 975.8 251.3 227.3 461.1 8.550 6.278 5.902 7.858 264.6 553.8 116.6 198.7 123.7 190.9 154.9 330.1 702.8 564.1 645.9 481.9 11.5 12,.

12.7 1.1.2 18.9 17.6 11.*6 12.6 701.1 9.421 162.7 337.8 4+ 442.2 295.2 336.4 281.2 524.5 9.5 5.19 9.6 8.5 9.1 11.4 10.*6 16.4 11.8 13.8 295.1 334.8 279.9 523.9 4.918 7.288 6.100 6.779 186.9 176.5 92.9 203.2 262.7 275.2 213 .8 405.5 8374.9 10885.1 1652.F/21.76 ks (900 C/150 If* F/6 0 .0 j67?-C/248 IMa) i 9921.2 12373.1 i.-:;qF/30.0 ksi (954 C/207 IMPa) 871.4 696.6 745.1 592.3 4+ 513.9 302.3 290.8 487.6 473.6 770.6 419.3 526.7 1M4. 8 279.5 615.8 458.4 7.5 8.3 11.2 16.7 15.6 12.6 12.9 11.4 9.8 8.4 1.1.8 18.1 14.1 10.4 10.6 5.8 14.*8 14.7 16.*1 32.3 23.*1 13.*8 16.4 22.1 21.9 15.2 23.4 30.8 13.8 13.8 1.1.0 23.6 8.9 9912.5 12366.0 869.*2 301.3 290.6 487.5 1124.5 278.1 615.*3 6.-107 6.474 9.409 7.376 8.061 7.*203 7.049 7.*173 5.000 179.6 451.4 203.5 197.7 263.6 529.5 190.0 301.1 260.4 255.8 417.*4 924.3 246.5 539.9 6329.2 8976.2 1750*/20.0/30.0 ]k3j* (954.C/138/207 MPa) 2057.9 13.1 26.7 24 2057.1 11.892. 1748.1 1905.7 0 1800 F/25.0 )csi

S

(982 C/172 *4

I

I

a a a C a 1082 .1 599.7 447.8 4+ 367.3 366.6 1511.6 577 .0 479.2 571.2 1060.8 891.4 12 .1 15.3 16.3 10.7 10.3 4.3 7.8 6.4 7.0 32.2 29.6 30.*4 13.1 14.5 1.1.6 18.*3 14.5 19.7 1081.5 1511.4 575.6 477.*7 1059.4 9.769 3.403 6.*239 5.057 5.354 268.4 870.9 908.5 331.8 266.2 1449.1 524.9 438.1 333.9 979.1 at 620 Hrs.

3250F/15. 0 J-MIP t/172 3.OOF/25. 0 -101p t/172 ksi 5381.8 7.2 at 3798.8 24.8 Ers., 1.250% 5381.2 Defamati m 4.066 4671.9 5293.3 2134.0 3csi ?pa) 510.5 446.2 518.1 734.4 1904.9 1981.0 1714.0 2097.7 6.1 7.4 8.1 6.7 4.9 5.9 4.0 5.0 31.3 32.0 36.1 27.6 20.8 18.1 9.4 16.4 509.1 445.1 579.6 733.7 1904.6 1974.9 173.1.4 2094.2 4.770 5.031 6.184 4.302 2.877 2.493 2.875 2.412 88.3 57.8 109. 0 80.5 1160.2 104.7 377.4 727.7 442.4 367.2 457.5 662.4 1888.0 1946.4 1633.7 2087 .0 19007/18.0 ksi Maduird Fran Blade Specimen (Airfoil) Mad~rsed Frun Blade Specimn~ (Trsverse Pot) Heat VG 33 Tst 1Psults t Selected rupture test speclUeri were reviewed mtalrapical1y folloingx testing.

None of the ruptured s~Iiens whidi were reviewed exhiibited any cservable signs of undesirable Mian~tuctral instability, ie., formation of Tcpoloically-Close-pakec (TCP) phases such as sigma, mu or others.

Aditionally, two test bars were exposed to 1600*F/39.2 ksi (870-C/270 MPa) condition for 200 hours. The respective bar gage setions were then reviewed andi no sign of deleteriouis ph~ase formnation was observed.

imtial Low, Cycle Fatigue (I.CF) test results are reported in Table 6 below. The results :of the strain-cotrolled tests undertaken at 1112*F (600*C are caqared to the typical :****,capabilities of selected other alloys, such as single crystal CMSX-2 alloy, DS and equiaxed CM 247 ILO alloy and DS Rend 80 H alloy.

TABLE 6 MIN iri CYCLE FMGdE 1112 -F (600-C); Strain-cotrolled (e TOTAL 106); R 0.25 Hz Alloy Cycles to Failure aMSX-1lC 12,130; 7,980 CMSX-210,000 DS C!4 247 IC 5,000 DS Mt80 H 1,500 CC (C 247 IC a d~ 0 Concrrent to the previouisly detale evaluations, fully heat treated aHSx-Jc test specimens were subjected to bare oxidation and hot corrosion testing.

7he~ results of hot corrosion tests perforned are reported in Table 7 below~. The tests wiere unerakn at 1292-F (700-C) and 1472-F (800-C) in a laboratory fun-ece utilizing an artificial ash plus S0 2 Metal loss data are reported as rean and maximmn values, as well as a percentage loss of the test pin errployei Data are reported for intervals of 100, 576 andl 1056 hours for the 1292*F (700'C) test, and 100, 576, 1056 and 5000 houirs for the 1472-F (800-C) test.

TABLE 7 CMSX-11C WYT (XEWI2 (crucible test with synxthetic slag) TES TEMPRA=IR: 700*C (1292'F) 100 34.5 39 2.70 576 90.5 102 7.05 1056 120.5 143.5 9.27 Mk=R~UR: 800*C (1472F) 100 56.5 112.5 4.41 576 366.5 394.5 26.97 1056 ,2520 2520 100.00 5000 2520 2520 100.00 Similarly, Figure 1 illustrates the results of additional hot corrosion tests undertaken with CMX-11C alloy and other alloys to 500 hours exposure in synthetic slag (GIV Type) plus .03 volume percent Sox in air.

The 500 hour tests were u dertaken at 1382, 1562, 1652"F, (750, 850 and 900"C). The results indicate that the CMSX-11C alloy provides extremely good corrosion resistance at all three test temperatures.

Subsequent testing utilizing an alternative slag, type FVV, with test tmperatures of 1472"F and 16529F (800, 900"C), was also undertaken. The 500 hour test results are reported in Table 8 below and illustrate a performance benefit derived from the CSX-11C alloys having a higher chrmium content cmpared to the 12.5% containing CMSX-1IB allay.

TABLE 8 CMSX-11C Alloy vs. IN 738 LC Alloy vs.

4. CMSX-1B Alloy Hot Corrosion Results presented represent depth of penetration after 500 hours exposure in synthetic slag (type FW) plus 0.03% SO x in air.

Test Temperature 800°C (1472"F) Alloy Maximum Penetration Averaae Penetration aMSX-IIC 160 .u 140 CSX-11B 350 gm 170 Test Temperature 900-C (1652°F) Allay Maximum Penetration Average Penetration CaSX-IIC i 150 gn 130 jn IN 738 IC 190 S MX-11B 220 i 150 28 Additional laboratory furnace, crucible type, artificial ash hot corrsion tests were performed. The results of these tests, undertaken at 1350"F (732"C) and 1650"F (899-C), are illustrated in Figures 2 and 3, respectively. In these tests, the specimens were coated with 1 mg./cm Na 2

SO

4 every 100 cycles and were cycled 3 times per day. Both tests were run to about 2400 hours. These results further demonstrate an inproved level of hot corrosion resistac obtained with the CHSX-11C alloy vs. the aKSX-11B material.

Further hot corrosion tests were performed with the CKX-1lC alloy, along with other materials for carparative purposes. In contrast to the aforementioned tests, these hot corrosion evaluations were performed in burner rigs, which is usually a preferred method of testing since the results adieved in burner rig tests generally give more representative indications of the way materials will perform in a gas turbine engine.

S

The burer rig tests were performe at 1652°F (9000C) and 1922"F (1050"C), and the test results are reported below in Tables 9 and 10, respectively.

The .35 in. (9 diameter x 3.9 in. (100 rn) long test pins utilized were mounted in a rotating cylindrical jig and exposed to a high speed gas stream. Other test conditions were as specified in the respective Tables.

TABLE 9 -900*C (1652 0 F) HOT CORROSION (BURNER RIG.) Weight Los In 200 Graiz~ As a F~irx±im of Tiw~ Grams As a Fun=ticn of

AIMOY

Hrs.

CMSX-11B CKSX-llc FSX 414

H

IN 738 LC 3N 939 CM 186 LC 300 400 500 .005 04 *.015 .075 .015 07 *.08 015 .005 .045 .275 .08 09 .195 .01 015 .04 .365 .10 14 .30 01 045 .04 .46 .15 15 .395 .03 .013 .085 .495 .195 06 .44 a.

a a a a. a a a *S C 0hmrar **Single Crystal 1 tmtperabire, time 2 brning gas flow rate 3 petroleum fl1w rate 4 salt water sul~furic oil 900*F 500 hrs (max) 6 NM /min.

9 Pi/hr.

6 cc/min.

6 c/min.

TABLE 1050°C (1922*F) HOT CORROSION (BURNER RIG.) Weight Lss 200 In Grams As a Functimn of Tine

ALLOY

Hrs.

100 300 400 500

*S

*5 a a CMX-11B CMSX-11C FSX 414 REPt 80 H IN 738 IC IN 939 CM 186 LC 0.1 0.04 0.2 0.18 0.1 0.1 0.6 0.7 0.05 0.39 0.38 0.43 0.22 2.9 1.15 1.22 0.5 0.47 1.35 0.26 1.55 0.65 1.45 2.09 0.45 1.65 0.9 1.68 2.33 0.65 13.7 6 Columnar Single Crystal

CONDITIMS

1 temperature, time 2 burning gas flow rate 3 petroleum flow rate 4 NaC1 solution sulphuric oil 1050* C 6 Nm/min 18 t/min 6 co/min 7 cc/min 500 hrs (max) SOx NaC1 Na 2

SO

4 :257 287 ppm :17.8 1 8 2 mg/m 3 mg/m The results of the tests indicate that the CMSX-11C alloy provided much better hot corrosion resistance than the IN 738 IC alloy at both test temperatures, and also performed superior to the CMSX-11B alloy.

Furthermore, Figure 4 illustrates that CMX-11C alloy provides an attractive blend of strength and hot corrosion resistance at 1922 *F (1050-C), and most notably, outperforms the commercially, widely used DS Rene 80 H alloy. It is believed that a similar analysis at 900*C would illustrate an even greater blend of capability.

S

CMSX-11C alloy oxidation tests were performed cr~rrent to the hot corrosion tests. Table 3-1 below reports the results of a crucible oxidation test performed at 17420F (950*C) for 1000 hour duration within a laboratory furnace. Mean and maxim= oxidation depth plus weight gain measurmnts recorded at 100 and 500 hour intervals are reported, as well as at test cculetion.

TABLE 11 TET TEM{PERA=IR: 950*C OXCI1MTIN DEIIH (micrns EXPOURE TM TAGH GAIN.

MEAN MXMJ 100 3.6 14.7 1. 30E-03 500 5.6 11.9 2.40E-03 1000 8.7 19.6 3.10E-03 5000 Slightly higher temperature oxidation test results are presented in Figure The data illustrated are the result of oxidation tests run at 18320F (1000*C) and to as long as 3000 hour duration. The tests were performed in an air Itnxsphere, and measured test specimen weight chiange as a function of time.

Th~e test tanperat2re was cycled to room tenperature on a once-per-hour basis.

7he test results indicateAthat the CMSX-11C alloy provides wdi better oxidation resistance than IN 738 LC, an alloy which is widely used thraighcut the industrial turbine industry.

Further oxidation test results are illustrated in Figure 6. In this particular test, the pins were cycled to roon tenperature 3 time per day frcm the 1850-F (1010-C) test temperature, and weight change measured as a function of time. The test was run to about 2400 hours and the results indicate that the CMSX-llC material provides much better oxidation resistance than the alloy IN 738 LC.

Burner rig oxidation testing was undertaken at 2192"F (1200*C), with the results presented in Table 12 below. Various alloys were tested within the same rotating carousel. Specimen weight loss was measured at intervals of 100, 200, 300, 400 and 500 hours. Additional test conditions are provided in the Table.

TABLE 12 1200*C (2192 0 F) OXIDATION (BURNER RIG.) 4 0 a a U a *a 4*U* a U Weight Inss In Grams As a Functicn of Tim 200 300 400 500 Hrs.

ALLOY

CMSX-11B .002 C4SX-l1C .002 FSX 414 .02 REN 80 H .002 IN 738 IC .005 IN 939 .016 CM 186 IC .002 DS Columnar Single Crystal O3NDITTCNS 1 tenperature, time 2 burning gas flow rate 3 petroleum flow rate 4 burning pressure 005 005 .077 005 .034 .038 .01 011 .009 .085 014 .049 .064 .01 .012 .01 .12 .20 .064 .077 .015 .026 .022 .125 .095 .113 .013 1200-c- 500 hrs (max) 6 Nm/min 18 20 t min 11 kgf/an The h.~rne rig oxidation test results illustrate that the c2msx-lc mterial provides extreuely good 2192-F (12 00- C) oxidation resistance in Lxprison to widely used industrial turbine blade andi vane materials.

An alloy strength ard 2192OF (1200*C) oxidation ctiparrison is illustrated in Figure 7. This Figure illustrates that the CMX-11C allay blended pbility is superior to directional solidified alloys such as RerA 80 H, FSX 414, IN 939 and IN 738 LC alloys.

Nhile this invention has been described with respect to particular embodients ~.thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. Thie appended claims .:and this invention generally should be construed to cover all such ob~vious *:forms and modifications which are within the true spirit ari scope of the present invention.

Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification, they are to be interpreted as specifying the presence of the stated features, integers, steps or components referred to, but not to preclude the presence or addition of one or more other feature, integer, step, component or group thereof.

34 The claims defining the invention are as follows:- 1. A hot corrosion resistant nickel-based superalloy consisting of the following elements in percent by weight:

C..

C.I

C

C

C

Chromium Cobalt Molybdenum Tungsten Tantalum Columbium Aluminium Titanium Hafnium Nickel Incidental Impurities said superalloy having a phasial stability number NV 3 B less than 14.2-15.5 2.0-4.0 0.30-0.45 4.0-5.0 4.5-5.8 0.05-0.25 3.2-3.6 4.0-4.4 0.01-0.06 balance about 2.45.

2. The superalloy of Claim 1 further comprising the following elements in percent by weight: Carbon Boron Zirconium about 0-0.05 about 0-0.03 about 0-0.03 A, \1 7'I

:OFO

02/06/99, mp 8 4 3 1

Claims (5)

1. 3. MiTe superal1oy of Claim 1 wherein the SnU of colunbium Plus hafnium is fron 0.06 to 0.31 percent by weight.
2. 4. The superalloy of Claim 1 wherein the Ti:A1 ratio is greater than 1. The superalloy of Clain 1 wherein the fran 7.2 to 8.0 percent by weight. sum of alumirwm plus titanium is
3. 6. The superalloy of Clain 1 wherein the Ta:W ratio, is greater than 1. The superalloy of Claim 1 wherein said sUperalloy has an i.ncreased resistance to oxidation. S. A single crystal article made fran the superalloy of Claim 1.
4. 9. The single crystal article of Claim 8 wherein the article is a cciponent for a turbine engine. The article of Claim 9 iui-~eein the component is a gas turbine blade or gas tubine vane.
5. 311. A single crystal asting d&aracterized by an br~sased resistanoe to hot corrosion, said casting being made fram a nickcel-based superalloy couprising 1/ 36 a the follow~ing elemnts in percent by weight: cobalt Molybdenum~ Tunsten Tantalumn Altuimi Titanium Hafnium Nickel Incidental 14.3-15.0 2.5-3.5 0.35-0.43 4.2-4.8 4.8-5.4 0.*05-0.12 3.3-3.5 4.1-4.3 0. 02-0.-05 balance a. a. a a. a said superaly having a phasia1 stability =1ber Nv, 3 B less than abouit 2.45. 12. The single crystal casting of Clain 10 further crrrising the followiing elemnts in percent by weight: Carbon Boran zirconium Rhenium. Silicon AMargaese, 0-0.05 0-0.03 0-0.*03 0-0.25 0-0.10 0-0.10 13. The single crystal casting of Claim 11 wherein the sum of columbium plus hafnium is from 0.06 to 0.31 percent by weight. 14. The single crystal casting of Claim 11 wherein the sum of aluminum plus titanium is frm 7.2 to 8.0 percent by weight. The single crystal casting of Claim 11 wherein both the Ti:Al ratio and the Ta:W ratio are greater than 1. 16. The single crystal casting of Claim 11 wherein said casting has an increased resistance to oxidation. 17. The single crystal casting of Claim 11 wherein said casting has an :.inreased crep-rtre strength. S s18. The single crystal casting of Claim 11 wherein said casting is a gas S burbine blade or gas bturbine vane. C S S S *S A single crystal casting characterized by an increased resistance to hot o :*'..:corrosion, said casting being made from a nickel-based superalloy camprising the following elements in percent by weight: Chromium 14.5 Cobalt Molybdenum 0.40 Tungsten 4.4 Tantalum 4.95 Columbium 0.10 z,38 7 r i; Wi 2 Aluminium 3.40 Titanium 4.2 Hafnium 0.04 Carbon 0-0.05 Boron 0-0.03 Zirconium 0-0.03 Rhenium 0-0.25 Silicon 0-0.10 Manganese 0-0.10 Nickel balance said superalloy having a phasial stability number N, 3 B less than about 2.45, wherein the sum of columbium plus hafnium is from 0.06 to 0.31 percent by weight, the sum of aluminium plus titanium is from 7.2 to 8.0 percent by weight, the Ti:AI ratio is greater than 1, and the Ta:W ratio is greater than 1. 20. The single crystal casting of Claim 19 wherein said casting is a gas turbine blade or gas turbine vane. 27 21. The superalloy of claim 1 substantially as hereinbefore described with reference to any one of the examples. DATED this 3 rd day of June 1999 CANNON MUSKEGON CORPORATION By their Patent Attorneys: CALLINAN LAWRIE //y u/1 <)39 39 i 22/06/99, mp8431.spec39 f ABSTRACT This invention relates to a hot corrosion resistant nickel-based superalloy cprising the follawing elements in percent by weight: frm about 14.2 to about 15.5 percent chromium, frnom about 2.0 to about 4.0 percent cobalt, fr- about 0.30 to about 0.45 percent molybdenum, frEa about 4.0 to about 5.0 percent tubrsten, frm about 4.5 to about 5.8 percent tantalum, from about 0.05 to about 0.25 percent columbium, from about 3.2 to about 3.6 S. 00 0 gOS* percent aluminum, from about 4.0 to about 4.4 percent titanium, from about 0.01 to about 0.06 percent hafnium, and the balance nickel plus incidental ipurities, the superalloy having a phasial stability number Nv 3 less than 0 about 2.45. Single crystal articles can be suitably made from the superalloy of this invention. The article can be a mcoponent for a gas turbine engine S and, more particularly, the ctponent can be a gas turbine blade or gas turbine vane. Sgo. 0 0000 o 0oo0 *055 o b:1444.jdd 'A