CA1212020A - Minor element additions to single crystals for improved oxidation resistance - Google Patents
Minor element additions to single crystals for improved oxidation resistanceInfo
- Publication number
- CA1212020A CA1212020A CA000409629A CA409629A CA1212020A CA 1212020 A CA1212020 A CA 1212020A CA 000409629 A CA000409629 A CA 000409629A CA 409629 A CA409629 A CA 409629A CA 1212020 A CA1212020 A CA 1212020A
- Authority
- CA
- Canada
- Prior art keywords
- hafnium
- additions
- silicon
- oxidation resistance
- alloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/52—Alloys
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Laminated Bodies (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Minor Element Additions to Single Crystals For Improved Oxidation Resistance Abstract The additions of minor additions of hafnium and silicon and mixtures thereof to nickel base superalloy single crystal articles provide significantly improved oxidation resistance. The oxidation resistance is im-proved both for the case of uncoated articles and in the case where a protective coating such as for example, a MCrAlY coating is present. For example the addition of .1% hafnium is observed to improve the oxidation re-sistance by a factor of 4 at 2100°F and a similar ad-dition improved the coated oxidation resistance by a factor of about 2.5 at 2150°F.
Description
ox Descrip'ion Minor element Additions to Single Crystals For Improved Oxidation Resistance Technical Field Nickel base superalloy single -rystal articles are provided with enhanced oxidation resistance by the ad-dition of .05-.2~ of a material selected from a group consisting of hafnium and silicon and mixtures thereof.
Additions of these elements improved the oxidation re-sistance of the articles in both coated and uncoated form.
Background Art Nickel base superalloys are widely used in gas tur-bine engines. Originally such alloys were used in con-ventionally cast form consisting of many randomly orient-ed e~uiaxea grains. Substantial property improvements were obtained by a casting technique known as directional solidification which was initially used to produce columnar grain articles consisting of a multiplicity of elongated oriented grains whose axis of elongation is constrained to be parallel to the axis of maximum stress A subsequent refinement permits the production of single crystal articles and these articles represent the state-of-the-art in superalloy technology. The present in-vention concerns tne improvement of the oxidation re-sistance of singie crystal superalloy articles through the addition of small amounts of hafnium and/or silicon.
Silicon is known as a constituent of superalloys and is shown for example in U.S. patents 2,621,122,
Additions of these elements improved the oxidation re-sistance of the articles in both coated and uncoated form.
Background Art Nickel base superalloys are widely used in gas tur-bine engines. Originally such alloys were used in con-ventionally cast form consisting of many randomly orient-ed e~uiaxea grains. Substantial property improvements were obtained by a casting technique known as directional solidification which was initially used to produce columnar grain articles consisting of a multiplicity of elongated oriented grains whose axis of elongation is constrained to be parallel to the axis of maximum stress A subsequent refinement permits the production of single crystal articles and these articles represent the state-of-the-art in superalloy technology. The present in-vention concerns tne improvement of the oxidation re-sistance of singie crystal superalloy articles through the addition of small amounts of hafnium and/or silicon.
Silicon is known as a constituent of superalloys and is shown for example in U.S. patents 2,621,122,
2,~94~605, 3,005,704, 3,411,8~8 and 3,524,744. Such minor additions have, to our }cnowledge, been made only to alloys intended for use in equiaxed form. We are unaware that silicon has even been intentionally added to single crystal nickel base superalloy articles.
Hafnium has also been used in nickel base super-alloy articles although to a lesser extent. U.S. patent
Hafnium has also been used in nickel base super-alloy articles although to a lesser extent. U.S. patent
3,005,705 suggests the use of .1-1.0% hafnium in a equiaxed alloy article. The benefit attributed to haf-nium in this patent is improved high temperature mechan-ical properties and it does not appear that any improve-ment in oxidation resistance was recognized. Hafnium has also been widely used in directional solidification columnar grained alloys where it provides improved trans-verse grain boundary ductility. This is described forexample in U.S. patent 3,677,747. Again, in this patent there is no discussion of enhanced oxidation resistance.
We are unaware that small hafnium additions have eve-r-been made to single crystals for any purpose and in fact it was previously thought that hafnium should be avoided in single crystal articles as discussed in U.S. patent
We are unaware that small hafnium additions have eve-r-been made to single crystals for any purpose and in fact it was previously thought that hafnium should be avoided in single crystal articles as discussed in U.S. patent
4,116,723.
Disclosure of Invention The present invention concerns the additions of from .05 to .2% of a material selected from a group con-sisting of hafnium, silicon and mixtures thereof to nickel base superalloy articles. The addition of haf-nium and silicon in these levels can provide from 2-4X
improvement in oxidation resistance. Improvement in oxidation resistance are observed in both coated an uncoated form. Other features and advantages will be apparent from the specification and claims and from the accompanying drawings.
Brief Description of Drawings Figure 1 shows the coated oxidation resistance of the single crystal article as a funetion of hafnium and silicon additions.
Figure 2a and 2b show the effect of hafnlum and silieon additions on gamma prime solvus temperature and incipient melting temperature.
Figure 3a and 3b show the effect of hafnium and silicon additions on rupture life and l ereep life.
Best Mode For Carrying Out The Invention This invention eoneerns a method for substantially improving the oxidation resistanee of niekel base single crystal superalloy articles in both uncoated and eoated forms. The invention results from the discovery that small additions of silieon and hafnium to the substrate alloy can significantly inerease the oxidation resis-tanee of the article. This result is somewhat surpris-ing and not predietable from the prior art sinee it was not formerly appreeiated that the degree of proteetion provided by eoatings employed on superalloy articles was so sensitive to the substrate alloy composition.
The essenee of the present invention is the addition of from about .05 to about .2 weight percent of silicon or hafnium or mixtures thereof to niekel superalloy single erystal articles. Such single erystal artieles OI
will in general contain from 5 to 18% chromium, at least5% of the material selected from the group consisting of aluminum and titanium with the provision that aluminum be present from 2 minimum of 2% to a maximum of 8% and the titanium be present in from a minimum of 1% to a maximum of 5%. Further, the alloy must contain at least
Disclosure of Invention The present invention concerns the additions of from .05 to .2% of a material selected from a group con-sisting of hafnium, silicon and mixtures thereof to nickel base superalloy articles. The addition of haf-nium and silicon in these levels can provide from 2-4X
improvement in oxidation resistance. Improvement in oxidation resistance are observed in both coated an uncoated form. Other features and advantages will be apparent from the specification and claims and from the accompanying drawings.
Brief Description of Drawings Figure 1 shows the coated oxidation resistance of the single crystal article as a funetion of hafnium and silicon additions.
Figure 2a and 2b show the effect of hafnlum and silieon additions on gamma prime solvus temperature and incipient melting temperature.
Figure 3a and 3b show the effect of hafnium and silicon additions on rupture life and l ereep life.
Best Mode For Carrying Out The Invention This invention eoneerns a method for substantially improving the oxidation resistanee of niekel base single crystal superalloy articles in both uncoated and eoated forms. The invention results from the discovery that small additions of silieon and hafnium to the substrate alloy can significantly inerease the oxidation resis-tanee of the article. This result is somewhat surpris-ing and not predietable from the prior art sinee it was not formerly appreeiated that the degree of proteetion provided by eoatings employed on superalloy articles was so sensitive to the substrate alloy composition.
The essenee of the present invention is the addition of from about .05 to about .2 weight percent of silicon or hafnium or mixtures thereof to niekel superalloy single erystal articles. Such single erystal artieles OI
will in general contain from 5 to 18% chromium, at least5% of the material selected from the group consisting of aluminum and titanium with the provision that aluminum be present from 2 minimum of 2% to a maximum of 8% and the titanium be present in from a minimum of 1% to a maximum of 5%. Further, the alloy must contain at least
5% of an element selected from the group consisting of up to 10% molybdenum, up to 15% tungsten, up to 12%
tantalum, up to 3% columbium, up to 7% rhenium and mix-tures thereof with the balance being essentially nickel.This composition is presented in U. S. Patent 4,116,723.
This patent also suggests that up to 3.5% hafnium might be preset. The present invention calls for the addition of from about .05 to .2% hafnium and the range suggested in the present invention is critical as will subsequently be demonstrated. The present invention was evaluated using a particular alloy denoted as Alloy 454 having a nominal composition of 10 weight percent chromium, 5%
cobalt, 5% aluminum, 1.5% titanium, 12% tantalum, 4%
tungsten, balance nickel. This single crystal alloy formulation is described in and claimed in U. S. Patent 4,209,348. This single crystal composition has an outstanding combination of properties but is generally representative of a wide range of such compositions.
Additions of .1%, .4, and .6 weight percent hafnium as well as additions of .1 and .3 weight percent silicon were made to this nominal alloy composition.
The resultant samples were tested under a variety of test conditions with the following resultsO Figure 1 shows the effect of minor additions of silicon and hafnium on coated oxidation resistance of Alloy 454. In `.~
l~Z~2~
this instance the coating was a coating known as an overlay coating with a nominal composltion of 22% cobalt, 20% chromium, 12% aluminum, and .8% yttrium This is a NiCoCrAlY overlay coating and is described in some S detail in U.S. patent 3,928,026. Overlay coatings typically contain 10-35% Cr, 8-25% Al, .1-1% Y balance selected from the group consisting of nickel and cobalt.
Small additions of other elements including silicon, hafnium and tantalum may also be present Overlay coatings are generally applied by vacuum vapor deposition process to produce a thin uniform adherent layer of the overlay coating alloy on the substrate surface. The data presented in Figure 1 is the test time to penetra-tion of the coating divided by the coating thickness.
This type of measurement gives a relatively accurate indication of coating performance and eliminates coating thickness as a variable. From the figure it can be seen that the additions of small amounts of hafnium and silicon to the substrate composition have a marked ef-fect on coated article life. The data in Figure 1 are the result of testing at 2150F using a burner rig test.
In this type of test, hot gases are generated by the combustion of jet fuel and these gases are impinged on the sample in test. The particular cycle employed in-25 cluded 29 minutes of exposure at 2150F followed by a 7 minute forced air cooling period. The purpose of the forced air cooling is to simulate the thermal fluctuations which occur during the operation of a gas turbine engine.
From Figure 1 it can be seen that the addition of about .1% silicon improves the coated oxidation life by about 90 or 100% while the addition of an equivalent amount of hafnium increases the coated oxidation life by about 150%. Hafnium is seen to be somewhat more effective ~21;~
than silicon in improving coated oxidation life and it is significant tha-t with additions of both hafnium and silicon that no significant increase in oxidation re-sistance is provided by additions of more than about .2 weight percent of the element. From figure l the broad range of element additiGns can be set at from about .05 to about .2%.
The effects of small additions of hafnium and silicon on the uncoated oxidation re~-istance of single crystal articles are described in Table 1. Alloy 454 is the previous single crystal material. The table shows the effect of small additions of hafnium and sili-con on the various parameters which are evaluated in oxidation testing. soth weight loss and maximum depth of penetration are substantially reduced by minor ele-ment additions. The column labeled oxidation resistance is determined by dividing the hours of testing into the maximum 2epth of penetration and the column labeled relative oxidation resistance compares the oxidation resistance of the various alloys to unmodified Alloy 454 material. From this latter column, it can be seen that additions of both hafnium and silicon significantly in-crease the uncoated oxidation resistance of the material.
Hafnium appears to be more effective than silicon at the same level and additions of hafnium in the amount of .~ weight percent are substantially more effective than .1% hafnium additions. As has been seen, this latter effect is not observed in testing of coated oxidation resistance, ~212~,~0 o o ;~
on l is a) X a O Pi .0 ED O
to on o c co o if o Pi ~~
H C ~~
h on 'r x ,1 a) .,, O X
H (I
a a En a:
O
o h to C) ¦ f h En O O o O
Lt~ Lr~ In O
O if ` or \~ \
ox o o ox o + + +
f o ~2~
From the preceding discussion it appears that hafnium is more effective than silicon in improving the oxidation resistance of single crystal articles in both coated and uncoated form. It is also obvious that hafnium has less deleterious effects on mechanical properties (as shown in Figure 3) and on incipient melting temperature (as shown in Figure 2). For this reason ha~nium is preferred over silicon.
Figures 2a and 2b illustrate the effect of hafnium and silicon additions on the gamma prime solvus tempera-ture and the incipient melting temperature of the sub-strate alloy. The gamma prime solvus temperature of the alloy is that temperature which must be exceeded if the gamma prime strengthening phase is to be dissolved into solid solution. The gamma prime solvus temperature must be approached and preferably exceeded for effective heat treatment of nickel base superalloys. The incipient melting temperature is that temperature above which localized melting of the superalloy will occur. For 2~ optimum heat treating results the gamma prime solvus temperature must be exceeded while the incipient melt-ing temperature should not be exceeded. Further, as a consequnce of the limitations of practical heat treating equipment, it is desirable that a temperature span of at least 10F, and preferably a greater span, exist between the gamma prime solvus and the incipient melting point.
In the case of single crystals it is not catastrophic if minor incipient melting occurs, but it is preferable to avoid incipient melting if possible. Turning now to Figure 2a the effect of hafnium additions on the gamma prime solvus and incipient melting temperatures of Alloy 454 are shown and it can be seen that for hafnium ad-ditions in excess of about .25 weight percent the ZIQ
incipient temperature lies below the gamma prime solvus leading to an undesirable heat treating situation. A
similar situation can be seen to exist in Figure 2b with respect to silicon additionsr The information presentea in Figures 2a and 2~ leads to the conclusion that ad-ditions of silicon and/or hafnium in excess of about .25~ are deleterious from the standpoint of heat treat-ment capability.
II1 metallurgy as in most highly developed art areas, it is unusual that a modification which improves one property will not have deleterious effect on other prop-erties. This is the case in the present invention.
Figures 3a and 3b show the effect of hafnium and silicon additions on the creep properties of A11O~5~. Figure 3a shows that additions of small amounts of hafnium lead to the steady decrease in both the rupture life and the time to l creep for specimens tested at 1600F with an applied load of 70 ksi. Figure 3b shows a similar ef-fect on the creep properties of Alloy 454 as a consequence of additions of small amount of silicon. However, it appears that small silicon additions have more of a deleterious effect on the creep properties than similar amounts of hafnium. The data presented in Figures 3a and 3b demonstrates another reason for limiting the silicor'hafnium additions to the lowest possible level consistent with the achievement of improved oxidation resistance.
While it has be., suggested in the prior art that additions of various elements including hafnium and silicon to the overlay coating composition itself pro-duces improvements in oxidation resistance, such prior art suggestions have to our knowledge been limited to ~z~
the suggestion that the elements be added to the coating itself and further have generally sugsested that ele-mental additions substantially in excess of those con-templated in the present invention be made. It appears that by making the addition o:E hafnium or silicon to the substrate alloy that the substrate 'herebv acts as a large reservoir of silicon and/or hafnium and that these elements diffuse into and through the coatinS
and aEfect the oxidation process at the free surface of the coating. Because of the relatively large amounts of hafnium and silicon which are present in the total substrate, the diffusion through the coating can occur for long periods of time without significantly de-creasing the effective amount of silicon and hafnium which is available. It is somewhat surprising, and unexpected, that these protective overlay coatings are so sensitive to the presence of silicon and hafnium in the substrate in such small amounts.
The overlay coatings derive their effectiveness from the development of a thin adherent scale of aluminum oxide on the free surface. It appears that the improvement in coated oxidation life results from some modification of this aluminum oxide layer by the sili-con and hafnium in the substrate. The other significant type of protective coating employed on superalloys is that referred to as aluminide coatings. Such coatings are produced by the diffusion of aluminum into the superalloy surface to produce a mcdified surface layer relatively rich in aluminum This aluminum rich surface layer develops an oxide on its free surface which pro-tects the coated part in a manner similar to that Of the protection derived by the overlay coatings. In view of this it is fully expected that additions of silicon %~
and hafniu~l to the substrate will produce a similar improvement in coated oxidation resistance of parts of superalloy single crystals which have been given a protective aluminide coating.
Finally, although the invention has been extensive-ly investigated with regard to an alloy known as Alloy 454, this alloy is representative of many other single crystal alloys and it is anticipated that similar results will be obtained on other al]oys. Another alloy containing esser amounts of tantalum and greater amounts of tungsten was also tested with and without the addition of l hafnium and an improvement of oxidation life of about 70~ was obtained. This tends to confirm the belief that the effect of silicon and hafnium will be generally observed in nickel base superalloys of the type previously described.
It should be understood that the invention is not limited to the particular embodiments shown and de-scribed herein, but that various changes and modifica-tions may be made without departing from the spirit and scope of this novel concept as defined by the following claims.
tantalum, up to 3% columbium, up to 7% rhenium and mix-tures thereof with the balance being essentially nickel.This composition is presented in U. S. Patent 4,116,723.
This patent also suggests that up to 3.5% hafnium might be preset. The present invention calls for the addition of from about .05 to .2% hafnium and the range suggested in the present invention is critical as will subsequently be demonstrated. The present invention was evaluated using a particular alloy denoted as Alloy 454 having a nominal composition of 10 weight percent chromium, 5%
cobalt, 5% aluminum, 1.5% titanium, 12% tantalum, 4%
tungsten, balance nickel. This single crystal alloy formulation is described in and claimed in U. S. Patent 4,209,348. This single crystal composition has an outstanding combination of properties but is generally representative of a wide range of such compositions.
Additions of .1%, .4, and .6 weight percent hafnium as well as additions of .1 and .3 weight percent silicon were made to this nominal alloy composition.
The resultant samples were tested under a variety of test conditions with the following resultsO Figure 1 shows the effect of minor additions of silicon and hafnium on coated oxidation resistance of Alloy 454. In `.~
l~Z~2~
this instance the coating was a coating known as an overlay coating with a nominal composltion of 22% cobalt, 20% chromium, 12% aluminum, and .8% yttrium This is a NiCoCrAlY overlay coating and is described in some S detail in U.S. patent 3,928,026. Overlay coatings typically contain 10-35% Cr, 8-25% Al, .1-1% Y balance selected from the group consisting of nickel and cobalt.
Small additions of other elements including silicon, hafnium and tantalum may also be present Overlay coatings are generally applied by vacuum vapor deposition process to produce a thin uniform adherent layer of the overlay coating alloy on the substrate surface. The data presented in Figure 1 is the test time to penetra-tion of the coating divided by the coating thickness.
This type of measurement gives a relatively accurate indication of coating performance and eliminates coating thickness as a variable. From the figure it can be seen that the additions of small amounts of hafnium and silicon to the substrate composition have a marked ef-fect on coated article life. The data in Figure 1 are the result of testing at 2150F using a burner rig test.
In this type of test, hot gases are generated by the combustion of jet fuel and these gases are impinged on the sample in test. The particular cycle employed in-25 cluded 29 minutes of exposure at 2150F followed by a 7 minute forced air cooling period. The purpose of the forced air cooling is to simulate the thermal fluctuations which occur during the operation of a gas turbine engine.
From Figure 1 it can be seen that the addition of about .1% silicon improves the coated oxidation life by about 90 or 100% while the addition of an equivalent amount of hafnium increases the coated oxidation life by about 150%. Hafnium is seen to be somewhat more effective ~21;~
than silicon in improving coated oxidation life and it is significant tha-t with additions of both hafnium and silicon that no significant increase in oxidation re-sistance is provided by additions of more than about .2 weight percent of the element. From figure l the broad range of element additiGns can be set at from about .05 to about .2%.
The effects of small additions of hafnium and silicon on the uncoated oxidation re~-istance of single crystal articles are described in Table 1. Alloy 454 is the previous single crystal material. The table shows the effect of small additions of hafnium and sili-con on the various parameters which are evaluated in oxidation testing. soth weight loss and maximum depth of penetration are substantially reduced by minor ele-ment additions. The column labeled oxidation resistance is determined by dividing the hours of testing into the maximum 2epth of penetration and the column labeled relative oxidation resistance compares the oxidation resistance of the various alloys to unmodified Alloy 454 material. From this latter column, it can be seen that additions of both hafnium and silicon significantly in-crease the uncoated oxidation resistance of the material.
Hafnium appears to be more effective than silicon at the same level and additions of hafnium in the amount of .~ weight percent are substantially more effective than .1% hafnium additions. As has been seen, this latter effect is not observed in testing of coated oxidation resistance, ~212~,~0 o o ;~
on l is a) X a O Pi .0 ED O
to on o c co o if o Pi ~~
H C ~~
h on 'r x ,1 a) .,, O X
H (I
a a En a:
O
o h to C) ¦ f h En O O o O
Lt~ Lr~ In O
O if ` or \~ \
ox o o ox o + + +
f o ~2~
From the preceding discussion it appears that hafnium is more effective than silicon in improving the oxidation resistance of single crystal articles in both coated and uncoated form. It is also obvious that hafnium has less deleterious effects on mechanical properties (as shown in Figure 3) and on incipient melting temperature (as shown in Figure 2). For this reason ha~nium is preferred over silicon.
Figures 2a and 2b illustrate the effect of hafnium and silicon additions on the gamma prime solvus tempera-ture and the incipient melting temperature of the sub-strate alloy. The gamma prime solvus temperature of the alloy is that temperature which must be exceeded if the gamma prime strengthening phase is to be dissolved into solid solution. The gamma prime solvus temperature must be approached and preferably exceeded for effective heat treatment of nickel base superalloys. The incipient melting temperature is that temperature above which localized melting of the superalloy will occur. For 2~ optimum heat treating results the gamma prime solvus temperature must be exceeded while the incipient melt-ing temperature should not be exceeded. Further, as a consequnce of the limitations of practical heat treating equipment, it is desirable that a temperature span of at least 10F, and preferably a greater span, exist between the gamma prime solvus and the incipient melting point.
In the case of single crystals it is not catastrophic if minor incipient melting occurs, but it is preferable to avoid incipient melting if possible. Turning now to Figure 2a the effect of hafnium additions on the gamma prime solvus and incipient melting temperatures of Alloy 454 are shown and it can be seen that for hafnium ad-ditions in excess of about .25 weight percent the ZIQ
incipient temperature lies below the gamma prime solvus leading to an undesirable heat treating situation. A
similar situation can be seen to exist in Figure 2b with respect to silicon additionsr The information presentea in Figures 2a and 2~ leads to the conclusion that ad-ditions of silicon and/or hafnium in excess of about .25~ are deleterious from the standpoint of heat treat-ment capability.
II1 metallurgy as in most highly developed art areas, it is unusual that a modification which improves one property will not have deleterious effect on other prop-erties. This is the case in the present invention.
Figures 3a and 3b show the effect of hafnium and silicon additions on the creep properties of A11O~5~. Figure 3a shows that additions of small amounts of hafnium lead to the steady decrease in both the rupture life and the time to l creep for specimens tested at 1600F with an applied load of 70 ksi. Figure 3b shows a similar ef-fect on the creep properties of Alloy 454 as a consequence of additions of small amount of silicon. However, it appears that small silicon additions have more of a deleterious effect on the creep properties than similar amounts of hafnium. The data presented in Figures 3a and 3b demonstrates another reason for limiting the silicor'hafnium additions to the lowest possible level consistent with the achievement of improved oxidation resistance.
While it has be., suggested in the prior art that additions of various elements including hafnium and silicon to the overlay coating composition itself pro-duces improvements in oxidation resistance, such prior art suggestions have to our knowledge been limited to ~z~
the suggestion that the elements be added to the coating itself and further have generally sugsested that ele-mental additions substantially in excess of those con-templated in the present invention be made. It appears that by making the addition o:E hafnium or silicon to the substrate alloy that the substrate 'herebv acts as a large reservoir of silicon and/or hafnium and that these elements diffuse into and through the coatinS
and aEfect the oxidation process at the free surface of the coating. Because of the relatively large amounts of hafnium and silicon which are present in the total substrate, the diffusion through the coating can occur for long periods of time without significantly de-creasing the effective amount of silicon and hafnium which is available. It is somewhat surprising, and unexpected, that these protective overlay coatings are so sensitive to the presence of silicon and hafnium in the substrate in such small amounts.
The overlay coatings derive their effectiveness from the development of a thin adherent scale of aluminum oxide on the free surface. It appears that the improvement in coated oxidation life results from some modification of this aluminum oxide layer by the sili-con and hafnium in the substrate. The other significant type of protective coating employed on superalloys is that referred to as aluminide coatings. Such coatings are produced by the diffusion of aluminum into the superalloy surface to produce a mcdified surface layer relatively rich in aluminum This aluminum rich surface layer develops an oxide on its free surface which pro-tects the coated part in a manner similar to that Of the protection derived by the overlay coatings. In view of this it is fully expected that additions of silicon %~
and hafniu~l to the substrate will produce a similar improvement in coated oxidation resistance of parts of superalloy single crystals which have been given a protective aluminide coating.
Finally, although the invention has been extensive-ly investigated with regard to an alloy known as Alloy 454, this alloy is representative of many other single crystal alloys and it is anticipated that similar results will be obtained on other al]oys. Another alloy containing esser amounts of tantalum and greater amounts of tungsten was also tested with and without the addition of l hafnium and an improvement of oxidation life of about 70~ was obtained. This tends to confirm the belief that the effect of silicon and hafnium will be generally observed in nickel base superalloys of the type previously described.
It should be understood that the invention is not limited to the particular embodiments shown and de-scribed herein, but that various changes and modifica-tions may be made without departing from the spirit and scope of this novel concept as defined by the following claims.
Claims (3)
1. A coated single crystal article having enhanced oxidation resistance consisting of a nickel superalloy substrate consisting of 5-18% chromium, at least 5% of the material selected from the group consisting of aluminum and titanium with the aluminum contents ranging from 2% to 8% and titanium content ranging from 1-5%, at least 5% of the material selected from the group consisting of up to 10% Mo, up to 15% W, up to 12% Ta, up to 3% Cb, up to 7% Re, 0 to 7% cobalt, which further contains from .05 to .2% of a material selected from a group consisting of hafnium and silicon and mixtures thereof balance nickel, said substrate having a coating thereon consisting of 10-35% chromium, 8-25%
aluminum, .1-1% yttrium balance selected from the group consisting of nickel, cobalt and mixtures thereof.
aluminum, .1-1% yttrium balance selected from the group consisting of nickel, cobalt and mixtures thereof.
2. An article as in claim 1, in which the additional element is silicon.
3. An article as in claim 1, which contains about 3-7% cobalt.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30180281A | 1981-09-14 | 1981-09-14 | |
| US301,802 | 1981-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1212020A true CA1212020A (en) | 1986-09-30 |
Family
ID=23164947
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000409629A Expired CA1212020A (en) | 1981-09-14 | 1982-08-18 | Minor element additions to single crystals for improved oxidation resistance |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5861244A (en) |
| CA (1) | CA1212020A (en) |
| DE (1) | DE3234090A1 (en) |
| FR (1) | FR2512838A1 (en) |
| GB (1) | GB2105748B (en) |
| IL (1) | IL66721A (en) |
| IT (1) | IT1152573B (en) |
Families Citing this family (36)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5399313A (en) * | 1981-10-02 | 1995-03-21 | General Electric Company | Nickel-based superalloys for producing single crystal articles having improved tolerance to low angle grain boundaries |
| US5154884A (en) * | 1981-10-02 | 1992-10-13 | General Electric Company | Single crystal nickel-base superalloy article and method for making |
| GR80048B (en) * | 1983-12-27 | 1984-11-30 | Gen Electric | Yttrium and yttrium-silicon bearing nickel-based superalloys especially useful as comptible coatings for advanced superalloys |
| GR80049B (en) * | 1983-12-27 | 1984-12-30 | Gen Electric | Nickel-based superalloys especially useful as compatible protective environmental coatings for advanced superalloys |
| US4721540A (en) * | 1984-12-04 | 1988-01-26 | Cannon Muskegon Corporation | Low density single crystal super alloy |
| US4677035A (en) * | 1984-12-06 | 1987-06-30 | Avco Corp. | High strength nickel base single crystal alloys |
| DE3683091D1 (en) * | 1985-05-09 | 1992-02-06 | United Technologies Corp | PROTECTIVE LAYERS FOR SUPER ALLOYS, WELL ADAPTED TO THE SUBSTRATES. |
| US5100484A (en) * | 1985-10-15 | 1992-03-31 | General Electric Company | Heat treatment for nickel-base superalloys |
| US6074602A (en) * | 1985-10-15 | 2000-06-13 | General Electric Company | Property-balanced nickel-base superalloys for producing single crystal articles |
| CA1291350C (en) * | 1986-04-03 | 1991-10-29 | United Technologies Corporation | Single crystal articles having reduced anisotropy |
| JP2787946B2 (en) * | 1988-09-09 | 1998-08-20 | 三菱マテリアル株式会社 | Ni-based single crystal superalloy with excellent high-temperature strength and high-temperature corrosion resistance |
| US5122206A (en) * | 1989-05-16 | 1992-06-16 | Mitsubishi Metal Corporation | Precipitation hardening nickel base single crystal cast alloy |
| US5679180A (en) * | 1995-06-22 | 1997-10-21 | United Technologies Corporation | γ strengthened single crystal turbine blade alloy for hydrogen fueled propulsion systems |
| DE19815473A1 (en) | 1998-04-07 | 1999-10-14 | Ghh Borsig Turbomaschinen Gmbh | Hot gas-carrying gas manifold of a gas turbine |
| DE60108212T2 (en) * | 2000-08-30 | 2005-12-08 | Kabushiki Kaisha Toshiba | Monocrystalline nickel-based alloys and methods of making and high temperature components of a gas turbine engineered therefrom |
| JP4521610B2 (en) * | 2002-03-27 | 2010-08-11 | 独立行政法人物質・材料研究機構 | Ni-based unidirectionally solidified superalloy and Ni-based single crystal superalloy |
| CH695497A5 (en) | 2002-04-30 | 2006-06-15 | Alstom Technology Ltd | Nickel-base superalloy. |
| AU2003255216B8 (en) * | 2003-10-21 | 2008-05-01 | Ansaldo Energia Ip Uk Limited | Nickel-base superalloy |
| WO2007037277A1 (en) * | 2005-09-27 | 2007-04-05 | National Institute For Materials Science | Nickel-base superalloy with excellent unsusceptibility to oxidation |
| US20090041615A1 (en) * | 2007-08-10 | 2009-02-12 | Siemens Power Generation, Inc. | Corrosion Resistant Alloy Compositions with Enhanced Castability and Mechanical Properties |
| JP5232492B2 (en) * | 2008-02-13 | 2013-07-10 | 株式会社日本製鋼所 | Ni-base superalloy with excellent segregation |
| EP2100982A1 (en) * | 2008-03-03 | 2009-09-16 | Siemens Aktiengesellschaft | Nickel base gamma prime strengthened superalloy |
| JP5467307B2 (en) * | 2008-06-26 | 2014-04-09 | 独立行政法人物質・材料研究機構 | Ni-based single crystal superalloy and alloy member obtained therefrom |
| CH699456A1 (en) * | 2008-09-08 | 2010-03-15 | Alstom Technology Ltd | High temperature cobalt-base superalloy. |
| JP5439822B2 (en) * | 2009-01-15 | 2014-03-12 | 独立行政法人物質・材料研究機構 | Ni-based single crystal superalloy |
| US20110076179A1 (en) * | 2009-03-24 | 2011-03-31 | O'hara Kevin Swayne | Super oxidation and cyclic damage resistant nickel-base superalloy and articles formed therefrom |
| JP5418589B2 (en) * | 2009-04-17 | 2014-02-19 | 株式会社Ｉｈｉ | Ni-based single crystal superalloy and turbine blade using the same |
| JP5526223B2 (en) * | 2010-03-29 | 2014-06-18 | 株式会社日立製作所 | Ni-based alloy, gas turbine rotor blade and stator blade using the same |
| JP5296046B2 (en) * | 2010-12-28 | 2013-09-25 | 株式会社日立製作所 | Ni-based alloy and turbine moving / stator blade of gas turbine using the same |
| GB2497128A (en) * | 2011-12-02 | 2013-06-05 | Rolls Royce Plc | Nickel-based alloys comprising 0.2-0.6 % by weight silicon |
| ES2654397T3 (en) | 2013-03-15 | 2018-02-13 | Haynes International, Inc. | Oxidation resistant Ni-Cr-Co-Mo-Al alloys, high strength, easy to manufacture |
| CN103243242B (en) * | 2013-05-09 | 2015-01-14 | 中国科学院金属研究所 | High-temperature alloy turbine blade repair material and repair process using same |
| EP2876176B1 (en) * | 2013-11-25 | 2017-06-21 | Mitsubishi Hitachi Power Systems, Ltd. | Ni-based casting superalloy and cast article therefrom |
| JP6425275B2 (en) * | 2016-12-22 | 2018-11-21 | 株式会社 東北テクノアーチ | Ni-based heat-resistant alloy |
| FR3073527B1 (en) * | 2017-11-14 | 2019-11-29 | Safran | SUPERALLIAGE BASED ON NICKEL, MONOCRYSTALLINE AUBE AND TURBOMACHINE |
| CN109811197B (en) * | 2019-01-09 | 2020-09-01 | 河北五维航电科技股份有限公司 | Preparation method of blade root gasket material for 700-DEG C steam turbine regulating stage |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2621122A (en) * | 1946-10-09 | 1952-12-09 | Rolls Royce | Alloy for heat and corrosion resisting coating |
| US3005704A (en) * | 1958-07-23 | 1961-10-24 | Union Carbide Corp | Nickel base alloy for service at high temperatures |
| US3008855A (en) * | 1959-01-26 | 1961-11-14 | Gen Motors Corp | Turbine blade and method of making same |
| US2994605A (en) * | 1959-03-30 | 1961-08-01 | Gen Electric | High temperature alloys |
| US3524744A (en) * | 1966-01-03 | 1970-08-18 | Iit Res Inst | Nickel base alloys and process for their manufacture |
| US3411898A (en) * | 1966-03-25 | 1968-11-19 | Union Carbide Corp | Nickel base alloy |
| US3676085A (en) * | 1971-02-18 | 1972-07-11 | United Aircraft Corp | Cobalt base coating for the superalloys |
| US3677747A (en) * | 1971-06-28 | 1972-07-18 | Martin Marietta Corp | High temperature castable alloys and castings |
| US3846159A (en) * | 1972-08-18 | 1974-11-05 | United Aircraft Corp | Eutectic alloy coating |
| US3973952A (en) * | 1973-06-11 | 1976-08-10 | The International Nickel Company, Inc. | Heat resistant alloy casting |
| US3928026A (en) * | 1974-05-13 | 1975-12-23 | United Technologies Corp | High temperature nicocraly coatings |
| US4116723A (en) * | 1976-11-17 | 1978-09-26 | United Technologies Corporation | Heat treated superalloy single crystal article and process |
| US4764225A (en) * | 1979-05-29 | 1988-08-16 | Howmet Corporation | Alloys for high temperature applications |
| GB2071695A (en) * | 1980-03-13 | 1981-09-23 | Rolls Royce | An alloy suitable for making single-crystal castings and a casting made thereof |
-
1982
- 1982-08-18 CA CA000409629A patent/CA1212020A/en not_active Expired
- 1982-09-01 FR FR8214924A patent/FR2512838A1/en active Granted
- 1982-09-03 IL IL66721A patent/IL66721A/en not_active IP Right Cessation
- 1982-09-07 GB GB08225449A patent/GB2105748B/en not_active Expired
- 1982-09-14 IT IT23257/82A patent/IT1152573B/en active
- 1982-09-14 DE DE19823234090 patent/DE3234090A1/en active Granted
- 1982-09-14 JP JP57161549A patent/JPS5861244A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IL66721A (en) | 1986-02-28 |
| IT8223257A0 (en) | 1982-09-14 |
| GB2105748A (en) | 1983-03-30 |
| FR2512838A1 (en) | 1983-03-18 |
| DE3234090C2 (en) | 1988-12-15 |
| IT1152573B (en) | 1987-01-07 |
| IL66721A0 (en) | 1982-12-31 |
| GB2105748B (en) | 1984-12-12 |
| DE3234090A1 (en) | 1983-04-28 |
| FR2512838B1 (en) | 1985-04-19 |
| JPS5861244A (en) | 1983-04-12 |
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