US3383206A - Nickel base alloy and article - Google Patents

Description

United States Patent 3,383,206 NICKEL BASE ALLOY AND ARTICLE Stanley T. Wlodek, Bethel Park, Pa., assignor to General Electric Company, a corporation of New York No Drawing. Continuation-impart of application Ser. No.

333,619, Dec. 26, 1963, now Patent No. 3,304,176, dated Feb. 14, 1967. This application Oct. 11, 1965, Ser. No. 494,966

5 Claims. (Cl. 75-171) This is a continuation-in-part of application Ser. No. 333,619, filed Dec. 26, 1963, now Patent No. 3,304,176.

This invention relates to nickel base alloys and, more particularly, to a solid solution type nickel base alloy of improved dynamic oxidation resistance.

In copending application Ser. No. 333,619, filed Dec. 26, 19 63 and assigned to the assignee of this invention there is described a nickel base alloy of improved oxidation resistance and fabrica-bility resulting from the addition of about 0.05 to less than 0.3 weight percent La to a Ni-Cr-Fe type nickel base alloy solution strengthened with either or both Mo and W.

The alloy of the copending application provides an unexpected improvement in oxidation resistance over similar known alloys. This improvement is now seen to be significant when used in a relatively static application such as in a furnace. However, it has been recognized that such an alloy requires further improvement for use under dynamic oxidation conditions. One example of a use under dynamic conditions is as a combustor material in a gas turbine engine where there is a rapid flow of combustion gases including excess oxygen.

A principal object of the present invention is to provide an alloy of the type described in the above identified c0- pending application but having improved oxidation resistance under dynamic oxidation conditions as well as under static oxidation conditions.

Another object is to provide such an alloy which, under dynamic oxidation conditions, will form an improved surface as a thermal reaction product in an oxidizing atmosphere to resist further oxidation of the alloy and to act as a barrier to internal oxidation.

Still another object is to provide an article including such an alloy and having an oxidation resistant surface.

These and other objects and advantages will be more readily recognized from the following detailed description and examples. These are intended to be exemplary of rather than any limitation on the scope of the invention.

It has been found that the above objects can be accomplished by combining lanthanum with certain spinel formers in the type of alloy described.

Briefly, the present invention provides an improved nickel base alloy of the solution strengthened type from which an improved article can be produced, the alloy consisting essentially of, by weight, 20-23% Cr; 8-10% Mo; 17-20% Fe; up to 0.15% C; up to 2% W; 0.05 to less than 0.3% La; 0.56% of the spinel forming elements selected from the group Co and Mn, the Co when selected being in the range of 13% and the Mn when selected 3,383,206 Patented May 14, 1968 being in the range of 0.53% with the balance nickel and incidental impurities.

In a preferred form, the alloy of the present invention includes O.1-0.2% La along with 1.5-2.5 Co and 0.5- 1.5% Mn.

During further evaluation of the alloy of the above identified co-pendiug application and its comparison with the alloy claimed in US. Patent 2,703,277, Spendelow et al., it was recognized that much of the advantage in oxidation resistance which resulted from the addition of the specified amount of lanthanum was lost during oxidation in high velocity combustion products. Consideration of the mechanism through which the lanthanum addition is effective indicated that unlike the known alloy of the above identified United States patent where-in the main reaction or surtace products were Cr O and spinel (NiCr O the reaction or surface products of the lanthanum modified alloy of the copending application consisted only of Cr O Although this rhombohedral surface scale was very protective under static exposure conditions, the absence of spinel overgrowths above the Cr O layer resulted in chromium volatilization in high velocity environments. This led to chromium depletion and an increased oxidation rate under such conditions.

As a result of understanding this mechanism, it was recognized that the control and definite inclusion of certain levels of strong spinel formers such as Mn and Co could provide an alloy having a combination of improved oxidation resistance under both static and dynamic conditions. However, other spinel formers such as iron already included in the alloy had little, if any, eliect on the reaction products.

The spinel formers manganese and cobalt were identified as impurities in the composition of the alloy of the copending application and of the alloy of the Spendelow et al. patent. They were not specifically included nor were their amounts controlled. In the Spendelow et a1. patent, cobalt is included as an impurity generally at less than 1% and in no event greater than about 2.5%; manganese is listed as an impurity permissible up to about 1% along with silicon and the like.

It has been recognized that when certain spinel formers such as Mn and Co are specifically controlled within the range of 0.5-6% for the total of such elements, a different kind of alloy surface is formed as an oxidation reaction product during and retained after both static and dynamic oxidation. Such a surface reaction product is different from that formed in either of the known alloys, and is highly stabilized. Its spinel portion is of the form Ni(Cr, Mn, Co) O rather than merely the NiCr O of the known alloys. The following Table I lists the types of surfaces found with each of the prior alloys and of the alloy of the present invention both under static and dynamic conditions. Example A is the alloy listed in US. 2,703,277, Example B is one form of the alloy of the copending application and Example 1 is the preferred form of the alloy of the present invention because of its relative ease of reduction. The compositions for these examples are found in Table II.

TABLE I.SURFACE COMPARISON AFTER 1,000 HRS. AT 2,000 F.

E Static Oxidation Dynamic Oxidation Outer Surface Subsurface Outer Surface Subsurface A CnO; plus Spinal A SiOz plus Spinel A Splnel A SiO lus S lnel A. B (Cr, LahOs do i3 2). p 1 (Cr, La)z0a plus Splnel B (Cr, La)z0s plus Spine] B- O4. Spinal B =N 1(Cr, Mn, C0)204;

TABLE II [Weight Percent-Balance Ni] Example Cr Mo Fe O W La Co Mn Si l. 2 17. 7 0. 10 0. 65 1. 0. 5 0. 9 9. (5 18. 3 0. 0.33 0. 09 0 0 0. 3 2 18. 5 0. 00 0. 04 0.17 1. 9 1.0 0. 8 8. G 18. G 0. 09 0. 43 0. 05 2. 4 2.8 O. 8 S. 5 18. 2 0. 10 0. 30 O. 17 3. 0 5 0. 8

These alloys were melted in a 100 pound vacuum induction furnace. The 1% Mn variation shown as Example 1 in Table II was successfully reduced to sheet and subjected to extensive oxidation evaluation and some mechanical testing.

As was mentioned above, the alloy of the copending application, shown in the tables by Example B has signii'icantly improved oxidation resistance under static conditions over the known alloy, represented by Example A. The following Table III gives a comparison of Examples A and B with each other and with the preferred form of the alloy of the present invention, represented by Example 1, under static oxidation resistance.

TABLE III-AVERAGE STATIC OXIDATION TESTING l Spalling of surface reaction products occurred on cooling. 2 A ditional 2 mils/side of line uniformly distributed internal oxide also oserved.

While Example B has oxidation resistance under static conditions better than does Example 1, the alloy of the present invention shown as Example 1 in Table III has static oxidation resistance at least equal to that of Example A. Although Example A experienced a lower weight gain at 2000 F. after 400 and 1000 hours static exposure, nevertheless, the reaction product surface of Example A spalled upon cooling. The surface of Examples B and 1 did not. The effectiveness of the reaction product surface to prevent internal oxidation is significantly greater in Alloys B and 1. Thus the alloy of the present invention has good oxidation resistance under static conditions, in general better than that of Example A.

The most significant difference between the alloy of the present invention and the other listed alloys is in dynamic oxidation resistance. Whereas the alloy of Example 13 is better under static oxidation conditions, it has significantly lower resistance in dynamic oxidation testing. This is shown more particularly in the data of Tables IV and V.

shown by the data of Table V. With regard to potential dimensional change of articles made from the alloy of Example 1 and after dynamic cyclic thermal experience, it is interesting to note that the alloy of Example 1 ex- 5 perienced no loss in width as a result of formation of its improved surface.

TABLE V.DYNA.\1IC OXIDATION TESTING IN FLAME TU N'EL [Average after 1,000 hours] 10 Avg. Depth Internal Oxi- Avg. width Example Temp, F. dation (mils/side) loss (m)i1s/ side Front Rear Thus the alloy of the present invention particularly represented by Example 1 is characterized by a combination of good static oxidation resistance and significantly better dynamic oxidation resistance.

The dynamic oxidation testing was conducted as thermal cyclic evaluations performed on 2.0" x 0.375" specimens.

The surface of all specimens to be used for oxidation testing were prepared by mechanical abrasion up to and including 600 grit paper. Final surface preparation consisted of vapor blasting the surface of the specimen using 1250 grit abrasive.

The specimens were supported in one end of a flame tunnel in a fire-brick with the majority of the specimen exposed to an uninterrupted gas/air flow of about 100 lbs./in. /hr. The tests were performed by cycling from 20 minutes at temperature followed by a 15 second blast of cooling air to reduce the specimen to a temperature of 1000 F. The entire cooling and heating cycle took approximately 30 seconds. Thus virtually the whole test period was spent at temperature. Weight and dimensional changes as shown in the above tables, as well as metallographic examination were used to determine the amount of oxidation. The following tensile properties of the alloy of the present invention particularly as represented by Example 1 were obtained on 60 mil sheet.

TABLE VL-AVERAGE TENSILE PROPERTIES Temp. Ultimate 0.2 percent 0.2 percent Percent F.) Tensile, Yield, Yield, Elong.

K s.i. K s.i. K s.i.

TABLE IV.-DYNAI\1IC OXIDATION TESTING IN FLAME TUNNEL 1,800 11, hours 2,000" F., hours Example The data of Table IV shows that the alloy of the present invention experiences a significantly lower weight loss than does either Examples A or B. More significantly in connection with its application as a useful article such as a combnstor in a gas turbine engine, the alloy of Example 1 has greatly improved resistance to internal oxidation compared with Examples A and B. This is too difiicult to reduce from an ingot. The particular combination of lanthanum along with controlled amounts of such effective spinel forms as manganese and cobalt in the type of alloy to which this invention relates provides an improved alloy having oxidation resistance under dynamic conditions significantly better than those known prior to this invention as well as good mechanical properties and good oxidation resistance under static conditions.

Although the present invention has been described in connection with specific examples such as of the effective spinel formers, it will be recognized by those skilled in the art other modifications and variations of this invention can exist. It is intended by the appended claims to cover such variations and modifications.

What is claimed is:

1. An improved nickel base alloy of the solution strengthened type consisting essentially of, by weight, 20-23% Cr; 8-10% Mo; 17-20% Fe; up to about 0.15% C; up to about 2% W; 0.05 to less than 0.3% La; 0.5-6% of the spinel forming elements selected from the group consisting of Co and Mn, the C0 when selected being in the range of 1-3% and the Mn when selected being in the range 0.5-3%; with the balance nickel and incidental impurities.

2. An improved nickel base alloy of the solution strengthened type consisting essentially of, by weight, 20-23% Cr; 8-10% Mo; 17-20% Fe; up to about 0.15% C; up to about 2% W; 0.05 to less than 0.3% La; 1-3% Co; 0.05-3% Mn; up to about 1% Si; with the balance nickel and incidental impurities.

3. An improved nickel base alloy of the solution strengthened type consisting essentially of, by weight, 20-23% Cr; 8-10%{Mo; 17-20% Fe; 0.05-0.15% C;

6 up to about 2% W; 0.1-0.2% La; 1.5-2.5% Co; 0.5-1.5% Mn; up to about 1% Si; with the balance nickel and incidental impurities.

4. An article including an alloy consisting essentially of, by weight, 20-23% Cr; 8-10% Mo; 17-20% Fe; up to about 0.15% C; up to about 2% W; 0.05 to less than 0.3% La; 0.5-6% of the spinel forming elements selected from the group consisting of Co and Mn, the Co when selected being in the range of 1-3% and the Mn when selected being in the range of 0.5-3%; with the balance nickel and incidental impurities; the alloy having a surface bonded with the alloy and comprising an integral combination of Cr and La oxides and a spinel of the Ni( Cr, Mn, Co) O type.

5. A combustion means for a gas turbine engine, the means including an alloy consisting essentially of, by weight, 20-23% Cr; 8-10% Mo; 17-20% Fe; up to about 0.15% C; up to about 2% W; 0.05 to less than 0.3% La; l-3% Co; 0.05-3% Mn; up to about 1% Si; with the balance nickel and incidental impurities; the alloy having a surface bonded with the alloy and comprising an integral combination of Cr and La oxides and a spinel of the Ni(Cr, Mn, Co) O type.

References Cited UNITED STATES PATENTS 2,703,277 3/1955 Spendelow et a1. -171 3,304,176 2/1967 Wlodek 75-171 3,304,177 2/1967 Wlodek 75-171 HYLAND BIZOT, Primary Examiner.

RICHARD O. DEAN, Examiner.

Claims (1)

1. AN IMPROVED NICKEL BASE ALLOY OF THE SOLUTION STRENGTHENED TYPE CONSISTING ESSENTIALLY OF, BE WEIGHT, 20-23% CR; 8-10% MO; 17-20% FE; UP TO ABOUT 0.15% C; UP TO ABOUT 2% W; 0.05 TO LESS THAN 0.3% LA; 0.5-6% OF THE SPINEL FORMING ELEMENTS SELECTED FROM THE GROUP CONSISTING OF CO AND MN, THE CO WHEN SELECTED BEING IN THE RANGE OF 1-3% AND THE MN WHEN SELECTED BEING IN THE RANGE 0.5-3%; WITH THE BALANCE NICKEL AND INCIDENTAL IMPURITIES.