Patent Application
20210252594
The present disclosure generally relates to articles of nickel based super alloys and methods of making same, specifically the articles have adaptive grain size.
Nickel based super alloys (NiSa) are corrosion resistant high-temperature alloys that are particularly useful in the aerospace industry. The machinability of NiSa has always been a challenge, however NiSa traditionally can only be cast in order to make aircraft and/or gas turbine engine parts. The resulting NiSa cast part has substantially uniform grain size distribution, and therefore substantially uniform mechanical properties across the part. When used to manufacture complex parts, the mechanical properties obtained after casting may not be optimal for the function of complex parts. Casting yields large coarse grain size because of the heat extraction limitations, which while providing good creep resistance is less optimal with respect to fatigue.
Powder bed fusion deposition by electron beam fusion (PBF-EB) is an alternative method, however it is not able to produce non-weldable alloy and thus it is difficult to locally control microstructure of the grains with PBF-EB.
Therefore, improvements are needed in the manufacture of NiSa parts.
In a first aspect there is provided a method of treating a nickel base super alloy (NiSa) article, the method comprising
i) obtaining the NiSa article having fine grains, the NiSa article having a uniform distribution of the fine grains and substantially uniform mechanical properties throughout;
ii) mechanically deforming one or more regions within NiSa article; and
iii) heat treating the NiSa article to obtain coarse grains in the one or more regions, the coarse grains having a size that is larger than that of the fine grains of the NiSa article outside of the one or more regions.
In one embodiment of the first aspect, the fine grains are equiaxed. In another embodiment of the first aspect the coarse grains are elongated. In a further embodiment of the first aspect, mechanical deformation is performed by plastic deformation. The mechanical deformation may be at least one of tensile deformation, compression deformation, cold rolling, hydroforming, peening and bending. In yet a further embodiment of the first aspect, the coarse grains are larger than the fine grains by a factor of between 2 to 80.
In a second aspect, there is provided a method of manufacturing a nickel base super alloy (NiSa) article, comprising: i) molding the NiSa article by powder metallurgy, the NiSa article having a uniform distribution of fine grains; ii) mechanically deforming one or more regions of the NiSa article; and iii) heat treating the NiSa article to obtain coarse grains in the one or more regions, the coarse grains having a size that is larger than that of the fine grains of the NiSa article outside of the one or more regions.
In one embodiment of the second aspect, the fine grains are equiaxed. In another embodiment of the second aspect the coarse grains are elongated. In a further embodiment of the second aspect, mechanical deformation is performed by plastic deformation. The mechanical deformation may be at least one of tensile deformation, compression deformation, cold rolling, hydroforming, peening and bending. In yet a further embodiment of the second aspect, the coarse grains are larger than the fine grains by a factor of between 2 to 80.
In a third aspect, there is provided an aircraft part comprising a body composed of nickel base super alloy (NiSa), the body including one or more regions within the body having coarse grains of NiSa, the body having fine grains of NiSa outside of the one more regions, the coarse grains having a size that is larger than that of the fine grains.
In one embodiment of the third aspect, the fine grains are equiaxed. In another embodiment of the third aspect the coarse grains are elongated. In a further embodiment of the third aspect, the one or more regions having an increased resistance to creep relative to a remainder of the body outside of the one or more regions. In yet a further embodiment of the third aspect, the coarse grains are larger than the fine grains by a factor of between 2 to 80.
The term “nickel based super alloy” or “NiSa” as used herein is understood to be nickel alloy, which may include nickel, iron-nickel, and between 0 to 10 weight % of Al, Co, Cr, Ta, Ti, Mo and/or other refractory metals as alloying elements, in respectively concentrations that will be appreciated and understood by the person skilled in the art. The person skilled in the art will also understand that such nickel based super alloys may also have other constituents. Such NiSa are suitable for and configured to be used in high temperature environments (e.g. greater than 1000 degrees C.).
Powder injection molding (PIM) or metal injection molding (MIM) of nickel alloys allows for the manufacture of complex parts that may be otherwise difficult to manufacture using other manufacturing processes. The as-molded surface finish of a part obtained after PIM may not require any additional post-molding operations to achieve requirements and feature definition that is fine enough to match or exceed any casting method's capabilities.
However, NiSa alloys are more difficult to manufacture than nickel alloys and are traditionally cast to create aircraft parts that are subject to high temperatures such as turbine blades and vanes. The term “aircraft part” as used herein is understood to include parts which are used within aircraft engines, such as but not limited to gas turbine engines, as well as parts of the aircraft's airframe itself. NiSa alloys are particularly desirable in the hot sections of aircraft engines because they have good resistance to creep, oxidation, sulfidation, and hot corrosion, as well as having a good stress rupture strength. NiSa alloys, due to their chemical composition, are however difficult to weld unless an additive manufacturing method such as powder bed fusion (PBF) is used.
The present disclosure provides NiSa alloys with adaptive grain size, and methods of manufacturing same, that are particularly suited for aircraft applications such as the hot sections of an aircraft engine.
Referring to
The next step 103 of the method 100 is to deform one or more regions of the NiSa article 102 by mechanical deformation 103, to obtain a deformed NiSa article 104. Mechanical deformation 103 may include any suitable deformation mechanism, such as plastic deformation. For example the mechanical deformation 103 may be one of tensile deformation, compression deformation, cold rolling, hydroforming, peening, spinning technics and bending. Other means for mechanically deforming the part may alternately be used. The one or more regions can be carefully chosen in order to optimize the overall mechanical properties of the final product NiSa article. For example, creep is more severe in conditions of high heat such as in the hot sections of an aircraft engine, and thus the desired regions of the article in the context of an aircraft engine could be the regions most exposed to the high heat conditions. These regions may include, for example, the exterior or peripheral regions of the part, and/or surfaces thereof that may be exposed during use to highest temperatures. After mechanical deformation 103, the deformed NiSa article 104 is subjected to a heat treatment 105. In one example, the heat treatment 105 is performed at a temperature between about 1000 and about 1200° C. for a duration of about 3 to about 5 hours. After the heat treatment 105, a NiSa article with adaptive grain size 106 is obtained.
The NiSa article 106 substantially retains the fine grains of the initial NiSa article 102 in the regions that were not subjected to mechanical deformation 103. The one or more regions that were subjected to mechanical deformation 103 will have coarse grains. The coarse grains have a size that is larger than the size of the fine grains. The coarse grains may be elongated. A coarse grain microstructure confers different mechanical properties to the one or more regions of the part. Coarse grains confer the one or more regions of the article an increased creep resistance and a decreased resistance to fatigue compared to the regions with fine grains. Therefore, it can be readily seen that a NiSa article can be tuned to have optimal mechanical properties through adaptive grain size microstructure. A NiSa part of an aircraft engine can be tuned to have coarse grains in the one or more regions that are most exposed to heat in order to increase the creep resistance thereby improving the overall performance of the part.
The deformation applied to a NiSa article can be controlled to precisely dictate the size of the coarse grains. The deformation can be a homogenous plastic deformation on one area. In further embodiments, the size of the coarse grains may be larger than the size of the fine grains by a factor of at least 2, 5, 20, 50 or 80.
Referring to
After the heat treatment 205, a NiSa article with adaptive grain size 206 is obtained. The NiSa article 206 substantially retains the fine grains of the initial NiSa article 202 in the one or more regions that were not subjected to mechanical deformation 203. The regions that were subjected to mechanical deformation 203 will have coarse grains. The coarse grains have a size that is larger than the size of the fine grains. The coarse grains may be elongated. A coarse grain microstructure confers different mechanical properties to the one or more regions of the part. Coarse grains confer the regions of the article an increased creep resistance and a decreased resistance to fatigue compared to the regions with fine grains. Therefore, it can be readily seen that a NiSa article can be manufactured to have optimal mechanical properties through adaptive grain sizes. The grain size of the one or more deformed regions can be controlled by controlling the % of mechanical deformation applied. The larger the % of mechanical deformation applied the smaller the grain sizes will be compared to smaller % of mechanical deformation. The grain size of the mechanically deformed regions will still be superior to the untreated regions. In one example, at least 2%, at least 2.5%), or at least 3% mechanical deformation is applied on one or more regions of the NiSa article.
In one embodiment, there is provided an aircraft part 300 that is made of NiSa (
In combustor panels creep mostly affects the stud. A simplified schematic of a part of a combustor panel 500 is provided in
In compressor blades, creep is most intense in the airfoil and fatigue is most intense at the fir tree. By manufacturing a blade with the method of the present disclosure, adaptive grain size allows the blade to have coarse grains at the airfoil to maximize creep resistance and fine grains at the fir tree to maximize the resistance to fatigue where it is needed. A simplified schematic of a blade 600 made of NiSa is shown in
A NiSa article was manufactured by MIM as described by the present disclosure. Three different regions were subject to different intensities of plastic deformation summarized in Table 1.
The grains of the NiSa region subjected to 2% plastic deformation had an increase in grain size of a factor between 40 to 80 compared to the non-deformed reference. The grains of the NiSa region subjected to 2.5% plastic deformation had an increase in grain size of a factor of 24 compared to the non-deformed reference. The grains of the NiSa region subjected to 3% plastic deformation had an increase in grain size of a factor of 20 compared to the non-deformed reference. The data for a NiSa cast material is shown for comparison. Microscopy images of the NiSa grains are shown in
The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.
