CA1038655A - Sulfidation resistant nickel-iron base alloy - Google Patents
Sulfidation resistant nickel-iron base alloyInfo
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- CA1038655A CA1038655A CA204,650A CA204650A CA1038655A CA 1038655 A CA1038655 A CA 1038655A CA 204650 A CA204650 A CA 204650A CA 1038655 A CA1038655 A CA 1038655A
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Abstract
ABSTRACT
A sulfidation-resistant alloy having high stress-rupture strength at about 1350-1500°F, containing about 0.02-0.08% carbon, 21-26% chromium, 52-58% nickel, 1-3.5%
molybdenum, 1.75-3.25% titanium, 0.75-2.25% aluminum, 0.50-2.00% columbium, up to 0.02% boron and the balance iron.
Articles such as valves and valve components made of the alloy are especially resistant to attack by sulfidation when used in heavy duty diesel engines in which fuels having a high sulfur content are used.
A sulfidation-resistant alloy having high stress-rupture strength at about 1350-1500°F, containing about 0.02-0.08% carbon, 21-26% chromium, 52-58% nickel, 1-3.5%
molybdenum, 1.75-3.25% titanium, 0.75-2.25% aluminum, 0.50-2.00% columbium, up to 0.02% boron and the balance iron.
Articles such as valves and valve components made of the alloy are especially resistant to attack by sulfidation when used in heavy duty diesel engines in which fuels having a high sulfur content are used.
Description
SPECIFICATION
This invention relates to nickel-iron base alloys, and, more particularly, to an alloy containing nickel, iron, chromium, molybdenum, titanium, aluminum and columbium criti-cally balanced to provide good sulfidation resistance combined with a high degree of hot strength at el~vated temperatures in the heat treated condition.
A number of alloys have hitherto been developed which were suitable for use under conditions requiring good hot strength and corrosion resistance at the elevated temperatures encountered in internal combustion engines. With the increasing use of fuels containing larger amounts of sulfu-, it is becQming more important that such alloys also have good resistance to sulfidation. Thus, at the present time, heavy duty diesel engines, which may burn high sulfur content fuels, require valves and valve components made of an alloy which not only has good hot strength at operating temperatures of up to about 1500F, but also has high resistance to sulfidation at such elevated temperatures. Alloy A, having a nominal composition of about 15% chromium, 7~ iron, 2.5% titanium, 1~ aluminum, 1%
columbium and the balance nickel, has been used as a valve alloy for diesel engines because of its high strength in the 1300-1500F temperature range. However, as the sulfur content of fuel has increased, Alloy A has shown poor resistance to sulfidation attack. This is a type of corrosion in which sulfides form at the surface of the alloy part, and, especially 103~6SS
when chromium is removed from the alloy matrix by this sulfidation corrosion, can result in the catastrophic failure of the part.
Alloy B, having desirable properties for use under stress in a sulfur-bearing atmosphere at elevated temperatures has a nominal composition of about 0.05% carbon, 0.30% manganese, 0.20% silicon, 29% chromium, 46% nickel, 20% cobalt, 2.30%
titanium, 1.20% aluminum, 0.70~ columbium, 0.006% boron and 0.50% maximum iron. The good hot strength at elevated temperatures and high resistance to sulfidation exhibited by this alloy make it especially desirable for use in making valves for diesel engines. However, the high percentage of cobalt and the rela-tively high expense involved in using iron-free alloying additions make this alloy relatively expensive.
Alloy C has a nominal composition of about 27% chromium, 37% nickel, 8% manganese, 2~ titanium, 1% aluminum and 25% iron.
This alloy is more resistant than X-751 alloy to sulfidation attack, but has a much lower strength in the 1300-1500F tempera-ture range. For this reason, Alloy C is not a good material for parts which must operate at such temperatures in diesel engines.
It is, therefore, a principal object of this invention to provide an alloy which has high strength and good resistance to sulfidation.
A more specific object is to provide a nickel-iron base alloy for making valves and valve components for use in heavy duty diesel engines and which is especially resistant to attack by sulfidation which occurs when high sulfur content fuels are used.
The foregoing, as well as additional objects and advantages of the present invention will be apparent from the 30 following description of a preferred embodiment of this invention and the accompanying drawing in which FIGURE 1 is a micrograph prepared from a specimen made from the alloy of the present invention, and which has undergone a sulfidation resistance test; and ` 1038655 FIGURE 2 is a similar micrograph of a specimen made of Alloy B; and FIGURE 3 is a similar micrograph of a specimen made of Alloy C.
In accordance with the present invention, there is provided a nickel-iron base alloy resistant to sulfidation at elevated temperatures in the range of about 1300 to 1500F and which has good hot strength and stress rupture life at elevated temperatures up to about 1500F when heat treated which con-sists essentially of the following elements in about the amountsindicated in the broad and preferred ranges given in approximate weight percent below. It is to be noted that it is not intended to be limited by the form of the following tabulation which has been used for convenience. It is intended that the upper and/or lower limits of one or more of the elements included in the broad range can be used with the upper and/or lower limits of one or more of the elements as included in the preferred range.
BroadIntermediatePreferred C 0.02-0.080.04-0.065 0.04-0.065 Mn 2 MaxØ25 Max. 0.20 Max.
Si 0.25 Max. 0.20 Max. 0.20 Max.
P 0.01 Max. 0.01 Max. 0.01 Max.
S 0.01 Max. 0.01 Max. 0.01 Max.
Cr 21-2622.0-24.5 22.0-23.5 Ni 52-58 53-56 54-56 Mo 1-3.51.5-2.5 1.5-2.5 Ti 1.75-3.252.25-2.75 2.25-2.75 Al 0.75-2.251.25-1.75 1.25-1.75 Cb 0. 50-20.75-1.50 0.75-1.50 B up to 0.02 0.002-0.008 0.002-0.008 The balance of the composition is iron, except for incidental impurities which, preferably, are kept low. The elements manganese, silicon, phosphorus and sulfur are impurities which should be present, preferably in the smallest amounts possible. Particularly, silicon is ~ept below about 0.25%, or preferably below about 0.20%, since higher amounts adversely affect the mechanical properties of the alloys. For best mechanical properties, particularly stress rupture life and ductility, manganese is kept below about 0.25% and better yet below about 0.20%. However, when the use for which the alloy is intended does not preclude it, then larger amounts of manganese . r~
up to about 1% and even up to about 2% can be present. Phosphorus and sulfur are limited to about 0.01% each because greater amounts adversely affect the mechanical properties, cleanliness, and forgeability of the alloy.
In the alloy of this invention, a minimum of about 0.02%
carbon is required to provide the desired deoxidation and the desired formation of carbides in the grain boundaries during aging.
Carbon ranging from about 0.04-0.065% is preferred. Because the main strengthening reaction of this alloy is the formation of gamma prime which is believed to be mainly composed of Ni3(Al,Ti), ex-cessive carbon tends to detract from the strength of this alloy by tying up titanium. Therefore, no more than about 0.08~ carbon should be present.
A minimum of about 21% chromium is required to provide the desired sulfidation resistance, particularly necessary in the environment to which valves are exposed in heavy duty diesel engine cylinders where sulfur-containing fuel oil is combusted. Too much chromium results in the formation of a chromium-rich phase, tenta-tively identified as a body centered cubic alpha phase, too much of which adversely affects the elevated temperature stress rupture life as well as the ductility at room temperature. Therefore, the chromium content is limited to about 26%, and is preferably kept in the range from about 22.0-24.5%.
Nickel is required to minimize the presence of phases other than the desired austenite and to take part in the reaction by which the alloy attains its desired strength. A minimum of about 52%, or preferably about 53-56%, is used for this purpose, while beyond about 58~, larger amounts of nickel will needlessly increase the cost of the alloy without providing any significant offsetting advantages.
For best all-around properties, that is, microstructural stability, sulfidation resistance and mechanical properties, the ` 103~655 chromium and nickel contents are adjusted to about 22-23.5~ chromi-um and about 54-56% nickel.
Molybdenum acts as a solid solution strengthener and, for this purpose, is present from about 1-3.5%, preferably 1.5-2.5%.
When present in amounts above about 3.5%, molybdenum may have an adverse effect on the sulfidation resistance and hot workability of the alloy.
As was noted, titanium is required for the formation of the gamma prime phase by which this alloy is strengthened, and, for this purpose, there should be at least about 1.75%. However, more than about 3.25% may adversely affect the hot workability of the alloy. Preferably, the titanium is present in the range of about
This invention relates to nickel-iron base alloys, and, more particularly, to an alloy containing nickel, iron, chromium, molybdenum, titanium, aluminum and columbium criti-cally balanced to provide good sulfidation resistance combined with a high degree of hot strength at el~vated temperatures in the heat treated condition.
A number of alloys have hitherto been developed which were suitable for use under conditions requiring good hot strength and corrosion resistance at the elevated temperatures encountered in internal combustion engines. With the increasing use of fuels containing larger amounts of sulfu-, it is becQming more important that such alloys also have good resistance to sulfidation. Thus, at the present time, heavy duty diesel engines, which may burn high sulfur content fuels, require valves and valve components made of an alloy which not only has good hot strength at operating temperatures of up to about 1500F, but also has high resistance to sulfidation at such elevated temperatures. Alloy A, having a nominal composition of about 15% chromium, 7~ iron, 2.5% titanium, 1~ aluminum, 1%
columbium and the balance nickel, has been used as a valve alloy for diesel engines because of its high strength in the 1300-1500F temperature range. However, as the sulfur content of fuel has increased, Alloy A has shown poor resistance to sulfidation attack. This is a type of corrosion in which sulfides form at the surface of the alloy part, and, especially 103~6SS
when chromium is removed from the alloy matrix by this sulfidation corrosion, can result in the catastrophic failure of the part.
Alloy B, having desirable properties for use under stress in a sulfur-bearing atmosphere at elevated temperatures has a nominal composition of about 0.05% carbon, 0.30% manganese, 0.20% silicon, 29% chromium, 46% nickel, 20% cobalt, 2.30%
titanium, 1.20% aluminum, 0.70~ columbium, 0.006% boron and 0.50% maximum iron. The good hot strength at elevated temperatures and high resistance to sulfidation exhibited by this alloy make it especially desirable for use in making valves for diesel engines. However, the high percentage of cobalt and the rela-tively high expense involved in using iron-free alloying additions make this alloy relatively expensive.
Alloy C has a nominal composition of about 27% chromium, 37% nickel, 8% manganese, 2~ titanium, 1% aluminum and 25% iron.
This alloy is more resistant than X-751 alloy to sulfidation attack, but has a much lower strength in the 1300-1500F tempera-ture range. For this reason, Alloy C is not a good material for parts which must operate at such temperatures in diesel engines.
It is, therefore, a principal object of this invention to provide an alloy which has high strength and good resistance to sulfidation.
A more specific object is to provide a nickel-iron base alloy for making valves and valve components for use in heavy duty diesel engines and which is especially resistant to attack by sulfidation which occurs when high sulfur content fuels are used.
The foregoing, as well as additional objects and advantages of the present invention will be apparent from the 30 following description of a preferred embodiment of this invention and the accompanying drawing in which FIGURE 1 is a micrograph prepared from a specimen made from the alloy of the present invention, and which has undergone a sulfidation resistance test; and ` 1038655 FIGURE 2 is a similar micrograph of a specimen made of Alloy B; and FIGURE 3 is a similar micrograph of a specimen made of Alloy C.
In accordance with the present invention, there is provided a nickel-iron base alloy resistant to sulfidation at elevated temperatures in the range of about 1300 to 1500F and which has good hot strength and stress rupture life at elevated temperatures up to about 1500F when heat treated which con-sists essentially of the following elements in about the amountsindicated in the broad and preferred ranges given in approximate weight percent below. It is to be noted that it is not intended to be limited by the form of the following tabulation which has been used for convenience. It is intended that the upper and/or lower limits of one or more of the elements included in the broad range can be used with the upper and/or lower limits of one or more of the elements as included in the preferred range.
BroadIntermediatePreferred C 0.02-0.080.04-0.065 0.04-0.065 Mn 2 MaxØ25 Max. 0.20 Max.
Si 0.25 Max. 0.20 Max. 0.20 Max.
P 0.01 Max. 0.01 Max. 0.01 Max.
S 0.01 Max. 0.01 Max. 0.01 Max.
Cr 21-2622.0-24.5 22.0-23.5 Ni 52-58 53-56 54-56 Mo 1-3.51.5-2.5 1.5-2.5 Ti 1.75-3.252.25-2.75 2.25-2.75 Al 0.75-2.251.25-1.75 1.25-1.75 Cb 0. 50-20.75-1.50 0.75-1.50 B up to 0.02 0.002-0.008 0.002-0.008 The balance of the composition is iron, except for incidental impurities which, preferably, are kept low. The elements manganese, silicon, phosphorus and sulfur are impurities which should be present, preferably in the smallest amounts possible. Particularly, silicon is ~ept below about 0.25%, or preferably below about 0.20%, since higher amounts adversely affect the mechanical properties of the alloys. For best mechanical properties, particularly stress rupture life and ductility, manganese is kept below about 0.25% and better yet below about 0.20%. However, when the use for which the alloy is intended does not preclude it, then larger amounts of manganese . r~
up to about 1% and even up to about 2% can be present. Phosphorus and sulfur are limited to about 0.01% each because greater amounts adversely affect the mechanical properties, cleanliness, and forgeability of the alloy.
In the alloy of this invention, a minimum of about 0.02%
carbon is required to provide the desired deoxidation and the desired formation of carbides in the grain boundaries during aging.
Carbon ranging from about 0.04-0.065% is preferred. Because the main strengthening reaction of this alloy is the formation of gamma prime which is believed to be mainly composed of Ni3(Al,Ti), ex-cessive carbon tends to detract from the strength of this alloy by tying up titanium. Therefore, no more than about 0.08~ carbon should be present.
A minimum of about 21% chromium is required to provide the desired sulfidation resistance, particularly necessary in the environment to which valves are exposed in heavy duty diesel engine cylinders where sulfur-containing fuel oil is combusted. Too much chromium results in the formation of a chromium-rich phase, tenta-tively identified as a body centered cubic alpha phase, too much of which adversely affects the elevated temperature stress rupture life as well as the ductility at room temperature. Therefore, the chromium content is limited to about 26%, and is preferably kept in the range from about 22.0-24.5%.
Nickel is required to minimize the presence of phases other than the desired austenite and to take part in the reaction by which the alloy attains its desired strength. A minimum of about 52%, or preferably about 53-56%, is used for this purpose, while beyond about 58~, larger amounts of nickel will needlessly increase the cost of the alloy without providing any significant offsetting advantages.
For best all-around properties, that is, microstructural stability, sulfidation resistance and mechanical properties, the ` 103~655 chromium and nickel contents are adjusted to about 22-23.5~ chromi-um and about 54-56% nickel.
Molybdenum acts as a solid solution strengthener and, for this purpose, is present from about 1-3.5%, preferably 1.5-2.5%.
When present in amounts above about 3.5%, molybdenum may have an adverse effect on the sulfidation resistance and hot workability of the alloy.
As was noted, titanium is required for the formation of the gamma prime phase by which this alloy is strengthened, and, for this purpose, there should be at least about 1.75%. However, more than about 3.25% may adversely affect the hot workability of the alloy. Preferably, the titanium is present in the range of about
2.25-2.75%.
Aluminum, which also takes part in the main strengthening reaction, should be present in the amount of at least about 0.75%
to ensure that the gamma prime phase is stable at such elevated temperatures as 1300-1500F, and the preferred range for aluminum is about 1.25-1.75%. Best results are obtained when the titanium/
aluminum ratio is greater than 1Ø More than about 2.25% aluminum adversely affects the hot workability of the alloy.
To form stable carbides which nucleate early in the solidification process, columbium is added, usually in amounts about 10 to 12 times the percent carbon present. A minimum of about 0.50~ columbium is used, and, preferably about 0.75-1.50%.
More columbium than that which forms carbides can be tolerated, and some small amount of columbium may be in the gamma prime phase, but above a total of about 2% merely adds to the cost of the alloy.
A small amount of boron, up to about 0.02%, contributes to the improved elevated temperature stress rupture life and duc-tility of this alloy. Preferably at least 0.002% is used, and bestresults are obtained with about 0.004-0.008%.
The alloy of this invention can be prepared using con-ventional practices, but it is preferably melted and cast into ` ~03B655 ingots by a multiple melting technique. For example, a heat can be first melted and cast as an ingot under vacuum in an induction furnace, and then that ingot used as a consumable electrode and remelted under vacuum. Alternatively, an electroslag remelting technique can be used.
The alloy is forged from a furnace temperature above about 1900F, preferably from about 2100 to 2150F, followed by solution treatment at about 1875 to 2100F for about 1 to 4 hours, or longer if necessary, preferably at about 2000F for 4 hours. After quenching in oil, or faster if desired, the alloy is aged by heating at about 1200 to 1550F for about 16 to 48 hours.
Preferably aging is carried out at about 1300F for 24 hours, but other aging treatments can be used including double aging treat-ments. By double aging is meant aging for about 2 to 8 hours near the upper end of the range, followed by a final age for about 16 to 48 hours at a temperature near the lower end of the 1200-1550F
range. As solution treated and aged, the alloy is fully austenitic.
The heat treatment of this alloy brings out a gamma prime phase which is a face centered cubic (FCC) structure, which helps give the alloy its good strength in the temperature range of 1300 to 1500F. There may also be a small amount of chromium rich alpha phase which is a body centered cubic structure similar to ferrite. Excessive amounts of this phase adversely affect room temperature ductility as measured by percent elongation in room temperature tensile tests.
As a further illustration of the present invention, two experimental vacuum induction heats, Examples 1 and 2, were pre-pared having compositions in accordance with this invention. The ingot of Example 2 was remelted as a consumable electrode under vacuum. For comparison, small heats of prior Alloys A, B and C
were prepared as was Example 1. The compositions of these five heats are given in Table I.
~' ` ~03~655 TABLE I
Ex. 1 Ex. 2 A B C
C.063 .062 .03 .09.055 Mn.17 .17 .05 .358.11 Si.17 .17 .05 .16.10 P<.005 <.005 .006 <.005 <.005 S.006 .003 .003 .005 .008 Cr23.30 23.78 15.63 28.3926.86 Ni54.13 54.84 Bal. Bal.37.50 Co - - - 19.45 Mo2.03 1.87 Ti2.55 2.50 2.49 2.281.97 Al1.43 1.48 1.18 1.16.99 Cb1.02 .99 1.01 .63 B.0062 .0053 .0024 .0057 .0056 FeBal. Bal. 7.65 .90Bal.
In each instance, the balance was iron or nickel, as indicated, except for incidental impurities.
To demonstrate and compare the sulfidation resistance of the alloys, specimens of Examples 1 and 2 and Alloys A, B and C
were machined from forgings to provide 0.300 in. diameter, 0.750 in.
long cylinders. Each was heat treated as shown in Table II.
TABLE II
_ S ol. q reat. ~
Temp Time Primary Final (F) (hrs) Cooll F hrs Cool F hrs Cool Ex.l 2000 4 OQ1500 4 AC 1350 24 AC
Ex.2 2000 4 OQ_ _ _ 1300 24 AC
B 1975 8 AC_ _ _ 1300 16 AC
C 2100 4 OQ_ _ _ 1300 24 AC
1 OQ - oil quenched AC - air cooled The specimens were placed vertically in one-inch diameter crucibles containing 7.0 grams of a molten salt mixture of 90% Na2SO4 and 10% NaCl, and allowed to stand for 100 hours at 1700F exposed to an air atmosphere. Then the samples were removed, and examination clearly demonstrated that only the specimens of Examples 1 and 2 and Alloy B had good resistance to sulfidation. In order to prepare micrographs of the tested specimens of Example 1, Alloy B
and Alloy C, cross-sectional sl~ces were taken at the height of the air/salt interface and mounted on plastic supports. Optical micrographs at 100x magnification were then taken of the outer edge of each slice and are shown respectively in FIGURES 1, 2 and
Aluminum, which also takes part in the main strengthening reaction, should be present in the amount of at least about 0.75%
to ensure that the gamma prime phase is stable at such elevated temperatures as 1300-1500F, and the preferred range for aluminum is about 1.25-1.75%. Best results are obtained when the titanium/
aluminum ratio is greater than 1Ø More than about 2.25% aluminum adversely affects the hot workability of the alloy.
To form stable carbides which nucleate early in the solidification process, columbium is added, usually in amounts about 10 to 12 times the percent carbon present. A minimum of about 0.50~ columbium is used, and, preferably about 0.75-1.50%.
More columbium than that which forms carbides can be tolerated, and some small amount of columbium may be in the gamma prime phase, but above a total of about 2% merely adds to the cost of the alloy.
A small amount of boron, up to about 0.02%, contributes to the improved elevated temperature stress rupture life and duc-tility of this alloy. Preferably at least 0.002% is used, and bestresults are obtained with about 0.004-0.008%.
The alloy of this invention can be prepared using con-ventional practices, but it is preferably melted and cast into ` ~03B655 ingots by a multiple melting technique. For example, a heat can be first melted and cast as an ingot under vacuum in an induction furnace, and then that ingot used as a consumable electrode and remelted under vacuum. Alternatively, an electroslag remelting technique can be used.
The alloy is forged from a furnace temperature above about 1900F, preferably from about 2100 to 2150F, followed by solution treatment at about 1875 to 2100F for about 1 to 4 hours, or longer if necessary, preferably at about 2000F for 4 hours. After quenching in oil, or faster if desired, the alloy is aged by heating at about 1200 to 1550F for about 16 to 48 hours.
Preferably aging is carried out at about 1300F for 24 hours, but other aging treatments can be used including double aging treat-ments. By double aging is meant aging for about 2 to 8 hours near the upper end of the range, followed by a final age for about 16 to 48 hours at a temperature near the lower end of the 1200-1550F
range. As solution treated and aged, the alloy is fully austenitic.
The heat treatment of this alloy brings out a gamma prime phase which is a face centered cubic (FCC) structure, which helps give the alloy its good strength in the temperature range of 1300 to 1500F. There may also be a small amount of chromium rich alpha phase which is a body centered cubic structure similar to ferrite. Excessive amounts of this phase adversely affect room temperature ductility as measured by percent elongation in room temperature tensile tests.
As a further illustration of the present invention, two experimental vacuum induction heats, Examples 1 and 2, were pre-pared having compositions in accordance with this invention. The ingot of Example 2 was remelted as a consumable electrode under vacuum. For comparison, small heats of prior Alloys A, B and C
were prepared as was Example 1. The compositions of these five heats are given in Table I.
~' ` ~03~655 TABLE I
Ex. 1 Ex. 2 A B C
C.063 .062 .03 .09.055 Mn.17 .17 .05 .358.11 Si.17 .17 .05 .16.10 P<.005 <.005 .006 <.005 <.005 S.006 .003 .003 .005 .008 Cr23.30 23.78 15.63 28.3926.86 Ni54.13 54.84 Bal. Bal.37.50 Co - - - 19.45 Mo2.03 1.87 Ti2.55 2.50 2.49 2.281.97 Al1.43 1.48 1.18 1.16.99 Cb1.02 .99 1.01 .63 B.0062 .0053 .0024 .0057 .0056 FeBal. Bal. 7.65 .90Bal.
In each instance, the balance was iron or nickel, as indicated, except for incidental impurities.
To demonstrate and compare the sulfidation resistance of the alloys, specimens of Examples 1 and 2 and Alloys A, B and C
were machined from forgings to provide 0.300 in. diameter, 0.750 in.
long cylinders. Each was heat treated as shown in Table II.
TABLE II
_ S ol. q reat. ~
Temp Time Primary Final (F) (hrs) Cooll F hrs Cool F hrs Cool Ex.l 2000 4 OQ1500 4 AC 1350 24 AC
Ex.2 2000 4 OQ_ _ _ 1300 24 AC
B 1975 8 AC_ _ _ 1300 16 AC
C 2100 4 OQ_ _ _ 1300 24 AC
1 OQ - oil quenched AC - air cooled The specimens were placed vertically in one-inch diameter crucibles containing 7.0 grams of a molten salt mixture of 90% Na2SO4 and 10% NaCl, and allowed to stand for 100 hours at 1700F exposed to an air atmosphere. Then the samples were removed, and examination clearly demonstrated that only the specimens of Examples 1 and 2 and Alloy B had good resistance to sulfidation. In order to prepare micrographs of the tested specimens of Example 1, Alloy B
and Alloy C, cross-sectional sl~ces were taken at the height of the air/salt interface and mounted on plastic supports. Optical micrographs at 100x magnification were then taken of the outer edge of each slice and are shown respectively in FIGURES 1, 2 and
3.
No micrograph was prepared from the specimen of Alloy A
because it was catastrophically attacked by the hot salt. The micrographs of FIGURES 1 and 2 show that the specimens of Example 1 and Alloy B were attacked only slightly, if at all, by the molten salt. On the other hand, the micrograph of FIGURE 3 shows that Alloy C suffered severe intergranular attack. These accel-erated sulfidation tests clearly show that the alloy of the present invention has about the same resistance to sulfur attack as Alloy B
and much greater resistance than Alloy C.
Standard A.S.T.M. stress rupture test specimens and tensile test specimens were prepared from each of the analyses of Table I except that tensile tests were not carried out in the case of Example 1 and, in the case of Alloy C, because the stress rupture life obtained was so low. Heat treatment of the specimens was as indicated in Table II. Stress rupture testing was carried out at 1350F under a load of 50,000 psi (50 ksi) and at 1500F
under a load of 30,000 psi (30 ksi), and the results are given in Table III. In each case, the duration of the test before failure is indicated in hours (hrs) under "Life", and percent elongation (El. %) and percent reduction in area (R.A. %) are also given. In Table IV, the results of tensile tests carried out at 70F and 1500F are indicated. In each instance, after the test temperature there is indicated the ultimate tensile strength (U.T.S.) followed by .2% yield strength (Y.S.), percent elongation and percent reduction in area.
103~655 TABLE III
Stress Rupture Data 1350F/50 ksi 1500F/30 ksi Life El. R.A. Life El. R.A.
(hrs) (%) (%) (hrs) (%) (%) Ex. 1 129 9.512.4 99.7 9.410.0 Ex. 2 133.2 4.5 4.4 61.2 3.97.7 Alloy A 100.0 8.0 Alloy B 198.5 6.9 6.9110.4 7.615.2 Alloy C 1.3 1.9 2.0 1.9 6.77.6 TABLE IV
Tensile Data Test Temp. U.T.S. .2~Y.S. El. R.A.
F (ksi) (ksi) %
. .
Ex. 2 70 175 111 30.638.2 Alloy A " 153 89 23 25 Alloy B " 183 120 30 41 Ex. 2 1500 104.5 91.5 12.414 Alloy A " 80 70 25 33 Alloy B ~I 109 92 11 14 An additional stress rupture specimen of Example 1, when aged by a single instead of a double heat treatment, had a stress rupture life at 1350F under 50 ksi of 277.6 hours, with a 7.4% elongation and a 12.4% reduction in area. Because of its combination of high strength at elevated temperatures and good resistance to sulfidation, the alloy of this invention is par-ticularly well suited for use in the fabrication of parts which must withstand stress and sulfur-bearing corrosive atmospheres at elevated temperatures. This alloy is considerably less expensive than Alloy B because Alloy B contains about 20~ cobalt and must be made with the more expensive iron-free forms of the alloying elements.
The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.
No micrograph was prepared from the specimen of Alloy A
because it was catastrophically attacked by the hot salt. The micrographs of FIGURES 1 and 2 show that the specimens of Example 1 and Alloy B were attacked only slightly, if at all, by the molten salt. On the other hand, the micrograph of FIGURE 3 shows that Alloy C suffered severe intergranular attack. These accel-erated sulfidation tests clearly show that the alloy of the present invention has about the same resistance to sulfur attack as Alloy B
and much greater resistance than Alloy C.
Standard A.S.T.M. stress rupture test specimens and tensile test specimens were prepared from each of the analyses of Table I except that tensile tests were not carried out in the case of Example 1 and, in the case of Alloy C, because the stress rupture life obtained was so low. Heat treatment of the specimens was as indicated in Table II. Stress rupture testing was carried out at 1350F under a load of 50,000 psi (50 ksi) and at 1500F
under a load of 30,000 psi (30 ksi), and the results are given in Table III. In each case, the duration of the test before failure is indicated in hours (hrs) under "Life", and percent elongation (El. %) and percent reduction in area (R.A. %) are also given. In Table IV, the results of tensile tests carried out at 70F and 1500F are indicated. In each instance, after the test temperature there is indicated the ultimate tensile strength (U.T.S.) followed by .2% yield strength (Y.S.), percent elongation and percent reduction in area.
103~655 TABLE III
Stress Rupture Data 1350F/50 ksi 1500F/30 ksi Life El. R.A. Life El. R.A.
(hrs) (%) (%) (hrs) (%) (%) Ex. 1 129 9.512.4 99.7 9.410.0 Ex. 2 133.2 4.5 4.4 61.2 3.97.7 Alloy A 100.0 8.0 Alloy B 198.5 6.9 6.9110.4 7.615.2 Alloy C 1.3 1.9 2.0 1.9 6.77.6 TABLE IV
Tensile Data Test Temp. U.T.S. .2~Y.S. El. R.A.
F (ksi) (ksi) %
. .
Ex. 2 70 175 111 30.638.2 Alloy A " 153 89 23 25 Alloy B " 183 120 30 41 Ex. 2 1500 104.5 91.5 12.414 Alloy A " 80 70 25 33 Alloy B ~I 109 92 11 14 An additional stress rupture specimen of Example 1, when aged by a single instead of a double heat treatment, had a stress rupture life at 1350F under 50 ksi of 277.6 hours, with a 7.4% elongation and a 12.4% reduction in area. Because of its combination of high strength at elevated temperatures and good resistance to sulfidation, the alloy of this invention is par-ticularly well suited for use in the fabrication of parts which must withstand stress and sulfur-bearing corrosive atmospheres at elevated temperatures. This alloy is considerably less expensive than Alloy B because Alloy B contains about 20~ cobalt and must be made with the more expensive iron-free forms of the alloying elements.
The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.
Claims (15)
1. A nickel-iron base alloy which is resistant to sulfidation at elevated temperatures in the range of about 1300° to 1500°F and which has good hot strength and stress rupture life at elevated temperatures up to about 1500°F when heat treated, which consists essentially by weight of about and the balance being essentially iron and incidental impurities.
2. The nickel-iron base alloy set forth in claim 1 containing about 0.002-0.008% boron.
3. The nickel-iron base alloy set forth in claim 1 containing about 0.004-0.008% boron.
4. The nickel-iron base alloy set forth in claim 2 containing about 0.04-0.065% carbon.
5. The nickel-iron base alloy set forth in claim 2 containing about 22.0-24.5% chromium.
6. The nickel-iron base alloy set forth in claim 2 containing about 1.5-2.5% molybdenum.
7. The nickel-iron base alloy set forth in claim 2 containing about 2.25-2.75% titanium and about 1.25-1.75% alu-minum.
8. The nickel-iron base alloy set forth in claim 2 in which the ratio of titanium to aluminum is greater than 1Ø
9. The nickel-iron base alloy set forth in claim 2 containing about 53-56% nickel.
10. The nickel-iron base alloy set forth in claim 2 containing about 0.75-1.50% columbium.
11. The nickel-iron base alloy set forth in claim 1 containing about
12. The nickel-iron base alloy set forth in claim 11 containing about 0.004-0.008% boron.
13. The nickel-iron base alloy set forth in claim 12 containing about
14. The nickel-iron base alloy set forth in claim 12 containing about
15. The nickel-iron base alloy set forth in claim 11 containing about
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US38176173A | 1973-07-23 | 1973-07-23 | |
| US47441874A | 1974-05-30 | 1974-05-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038655A true CA1038655A (en) | 1978-09-19 |
Family
ID=27009505
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA204,650A Expired CA1038655A (en) | 1973-07-23 | 1974-07-12 | Sulfidation resistant nickel-iron base alloy |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1038655A (en) |
| IT (1) | IT1017341B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3048178A1 (en) * | 2015-01-26 | 2016-07-27 | Daido Steel Co.,Ltd. | Engine exhaust valve for large ship and method for manufacturing the same |
-
1974
- 1974-07-12 CA CA204,650A patent/CA1038655A/en not_active Expired
- 1974-07-22 IT IT2543174A patent/IT1017341B/en active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3048178A1 (en) * | 2015-01-26 | 2016-07-27 | Daido Steel Co.,Ltd. | Engine exhaust valve for large ship and method for manufacturing the same |
| US10557388B2 (en) | 2015-01-26 | 2020-02-11 | Daido Steel Co., Ltd. | Engine exhaust valve for large ship and method for manufacturing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1017341B (en) | 1977-07-20 |
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