Sublayer for a nickel-based superalloy for enhancing the lifetime of the parts and implementation method thereof

Abstract

A nickel-based superalloy part includes a nickel-based superalloy substrate, and a metal sublayer covering the substrate, wherein the metal sublayer includes a first and a second layer, the first layer being located between the substrate and the second layer, the first layer including a first -Ni.sub.3Al phase and a second -Ni phase, the second layer including a first -Ni.sub.3Al phase, a second -Ni phase and a third -NiAl phase, the average atomic fraction of aluminum in the second layer being strictly greater than the average atomic fraction of aluminum in the first layer.

Claims

1. A nickel-based superalloy part comprising: a nickel-based superalloy substrate; and a metal sublayer covering the substrate, wherein the metal sublayer comprises a first and a second layer, said first layer being located between the substrate and the second layer, said first layer comprising a first -Ni.sub.3Al phase and a second -Ni phase, said second layer comprising a first -Ni.sub.3Al phase, a second -Ni phase and a third -NiAl phase, an average atomic content of aluminum in the second layer being greater than the average atomic content of aluminum in the first layer, and in which a total content of -Ni in the metal sublayer is comprised between 5.0% and 20.0% by mass, a total content of -Ni.sub.3Al in the metal sublayer is comprised between 40.0% and 90.0% by mass and a total content of -NiAl in the metal sublayer is comprised between 5.0% and 40.0% by mass relative to the total weight of the sublayer, wherein the first layer comprises a plurality of first areas, wherein a lowermost area of the plurality of first areas comprises an average atomic content of aluminum greater than an average atomic content of aluminum of the substrate, wherein an aluminum content difference between the substrate and the lowermost area of the plurality of first areas is up to 4%, and each remaining first area of the plurality of first layers comprising an average content of aluminum greater than an average atomic content of aluminum of an area directly below, wherein each aluminum content difference is up to 4%, said first areas having a thickness of 1 m to 5 m, and wherein the second layer comprises a plurality of second areas, wherein a lowermost area of the plurality of second areas comprises an average atomic content of aluminum greater than an average atomic content of aluminum of an uppermost area of the plurality of first areas, wherein an aluminum content difference between the uppermost area of the plurality of first areas and the lowermost area of the plurality of second areas is up to 4%, and each remaining second area of the plurality of second layers comprising an average content of aluminum greater than an average atomic content of aluminum of an area directly below, wherein each aluminum content difference is up to 4%, said second areas having a thickness of 1 m to 5 m.

2. A nickel-based superalloy part comprising: a nickel-based superalloy substrate; and a metal sublayer covering the substrate, wherein the metal sublayer comprises a first and a second layer, said first layer being located between the substrate and the second layer, said first layer comprising a first -Ni.sub.3Al phase and a second -Ni phase, said second layer comprising a first -Ni.sub.3Al phase, a second -Ni phase and a third -NiAl phase, an average atomic content of aluminum in the second layer being greater than the average atomic content of aluminum in the first layer, and in which a total content of -Ni in the metal sublayer is comprised between 5.0% and 20.0% by mass, a total content of -Ni.sub.3Al in the metal sublayer is comprised between 40.0% and 90.0% by mass and a total content of -NiAl in the metal sublayer is comprised between 5.0% and 40.0% by mass relative to the total weight of the sublayer, wherein the first layer comprises a plurality of first areas, each of the first areas of the first layer comprising an average content of aluminum greater than an average atomic content of aluminum of an area directly below wherein a content difference is up to 4%, said first areas having a thickness of 1 m to 5 m, and wherein the second layer comprises a plurality of second areas having an average atomic content of aluminum greater than an average atomic content of aluminum of an area directly below wherein a content difference is up to 4%, said second areas having a thickness of 1 m to 5 m.

3. The part according to claim 2, wherein a total content of hafnium Hf in the metal sublayer is comprised between 0.2% and 2.0% by mass relative to the total weight of the metal sublayer.

4. The part according to claim 2, wherein the average atomic content of aluminum of the first layer is between 2% and 4% higher than an average atomic content of aluminum of the substrate.

5. The part according to claim 2, wherein the average atomic content of aluminum of the second layer is between 2% and 4% higher than the average atomic content of aluminum of the first layer.

6. The part according to claim 2, wherein the total content of phase in the substrate is comprised between 20% and 40% by mass relative to the total weight of the substrate.

7. A method for preparing a part according to claim 2, comprising depositing each layer of the metal sublayer by a physical method in the vapor phase.

8. The preparation method according to claim 7, wherein the method is carried out in a single enclosure by co-evaporation or co-sputtering of several sources disposed in the single enclosure.

Description

DESCRIPTION OF EMBODIMENTS

(1) FIG. 1 is a schematic representation of a part according to one embodiment of the invention.

(2) FIG. 2 is a micrograph of a part according to one embodiment of the invention.

(3) FIG. 3 schematically shows a physical vapor deposition enclosure according to one embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

(4) Embodiments of the invention are now described by means of figures. However, the invention is not limited to these embodiments alone. The figures are for illustrative purposes and should not be construed as limiting the invention.

(5) FIG. 1 schematically shows a part 100 according to the invention.

(6) The part comprises a substrate 10, made of nickel-based superalloy, and a sublayer, comprising a first layer 11 and a second layer 12.

(7) As described above, the first layer 11 comprises an average atomic content of aluminum greater than that of the substrate 10.

(8) The scope of the invention is not departed from, when the first layer 11 comprises a plurality of areas, each comprising an average atomic content of aluminum greater than that of the underlying area.

(9) For example, it is possible for the first layer 11 to be composed of a plurality of areas each having a thickness comprised between 1 m and 5 m, the average atomic content of aluminum in each of the areas being greater than the average atomic content of aluminum of the underlying area.

(10) For example, the average atomic content of aluminum in each area of the first layer can be up to 4% greater, or else between 2 and 4% greater than the average atomic content of aluminum of the underlying area.

(11) Also, the part 100 comprises a second layer 12 whose average aluminum content is greater than the average aluminum content of the first layer 11.

(12) The scope of the invention is not departed from when the second layer 12 comprises a plurality of areas, each comprising an aluminum concentration greater than that of the underlying area.

(13) For example, it is possible for the second layer 12 to be composed of a plurality of areas having a thickness comprised between 1 m and 5 m, the average aluminum content in each of the areas being greater than the average aluminum content of the underlying area.

(14) For example, the average atomic content of aluminum in each area of the second layer can be up to 4% greater, or else between 2% and 4% greater than the average atomic content of aluminum of the underlying area.

(15) It is also possible for the first 11 and the second layer 12 to each comprise several areas as described above.

(16) In one embodiment not shown, the first area of the first layer comprises an average atomic content of aluminum 2 to 4% greater than the average atomic content of aluminum in the substrate, the second area of the first layer comprises an average atomic content of aluminum of 2 to 4% greater than the average atomic content of the first area, and so on until the second layer, the first area of which comprises an average atomic content of aluminum of 2% to 4% greater than the last area of the first layer, and so on until the last area of the second layer. As above, the areas have a thickness comprised between 1 m and 5 m.

(17) The progressive variation of the aluminum content allows, in all the embodiments considered above, to obtain a sublayer whose upper portion has an average atomic content of aluminum greater than that of the substrate, while minimizing the interdiffusion effects or the creation of secondary reaction areas thanks to a progressive variation of the average atomic content of aluminum.

(18) As described above, it is understood that the last area of the second layer comprises the -Ni, -Ni.sub.3Al and -NiAl phases.

(19) In one embodiment, the first layer 11 comprises between 1 and 4 areas, and the second layer 12 comprises between 1 and 4 areas.

(20) In one embodiment, the first layer 11 comprises between 1 or 2 areas, and the second layer 12 comprises between 1 or 2 areas.

(21) In one embodiment, the first layer 11 comprises a single area, and the second layer 12 comprises a single area.

(22) It has also been observed that a sublayer as described above allows, if desired, to deposit a thermal barrier layer on the face opposite the substrate of the second layer, in particular guaranteeing good adhesion of the latter.

(23) The gradual increase in the average atomic content of aluminum in a sublayer as proposed allows to ensure that each of the layers forming the sublayer is sufficiently close in composition to have a high adhesion with the directly underlying layer. The gradual increase allows to go from the first layer to the second layer without having to change the deposition method. Indeed, the -NiAl phase appears naturally at high aluminum contents and thus one simply goes from the first to the second layer.

(24) In addition, the presence of numerous areas in the first and second area increases the number of grain boundaries, which further slows down the interdiffusion of nickel or aluminum between the layers.

(25) In one embodiment, chromium is also present in the first and second layers. The amount of chromium can be adjusted depending on the exact properties desired for the sublayer.

(26) In one embodiment, the chromium content in each of the first and second layers varies opposite to the aluminum content.

(27) In one embodiment, the increase in the average atomic content of aluminum in the metal sublayer or, where applicable, in each of the areas of each of the layers of the sublayer is fully compensated by a decrease in the average atomic content of chromium in said sublayer.

(28) In one embodiment, the average atomic content of chromium in a layer, or where appropriate an area of a layer, can be comprised between 7% and 17%.

(29) Of course, the chromium content is chosen such that it does not affect the desired / or // structures for the first and second layers.

(30) FIG. 2 is a micrograph obtained by scanning electron microscopy of a part according to one embodiment of the invention.

(31) The substrate 20 is covered with a first layer 21 and a second layer 22.

(32) On the micrograph shown in FIG. 2, the and phases 211 appear lighter than the phases 221.

(33) In one embodiment, the deposition can be carried out by physical vapor deposition. Mention may in particular be made of deposition methods by cathode sputtering, by pulsed laser ablation, by Joule evaporation or else by electron impact.

(34) Preferably, the deposition method is selected from magnetron cathode sputtering or evaporation.

(35) FIG. 3 schematically shows a device allowing to carry out a deposition by magnetron cathode sputtering.

(36) In a chamber 301, a gas is introduced through the inlet 306 and a plasma is generated between the target 305 disposed near a magnet 304 and the substrate 311.

(37) For example, the following parameters, taken in their usual definition for a magnetron cathode sputtering method, allows to obtain a sublayer conforming to a part of the invention. The ion bombardment can be carried out with a potential comprised between 200 V to 400 V for 10 to 30 minutes. The deposition is performed at a power density comprised between 3 to 10 W/cm.sup.2, heating during deposition is comprised between 200 to 700 C., the bias is comprised between 150 V to 300 V, and the pressure is comprised between 0.1 and 2.0 Pa.

(38) In one embodiment, several targets corresponding to the materials to be deposited are introduced into the physical vapor deposition chamber. It is thus possible to create the sublayer layer by layer, or if necessary area after area, in a single enclosure, by adjusting the deposition conditions to ensure that the composition of each layer, or if necessary each area of the first layer then the second layer, has the desired composition.

EXAMPLE

(39) Several compositions comprising elements in different contents were simulated with the JPMATPro-V10 software. For each of these compositions, the content of each of the -Ni, -Ni.sub.3Al and -NiAl phases was determined by the software.

(40) In table 1, the contents of the elements are given in atomic percentages and the contents of the phases are expressed in mass percentages.

(41) It is observed that the content of each of the -Ni, -Ni.sub.3Al and -NiAl phases of compositions 1 to 3 satisfy the desired conditions for the second layer of claim 1, while compositions 4 and 5 do not satisfy said conditions.

(42) TABLE-US-00001 TABLE 1 Ni Al Cr Co Hf Pt Si Ta W 1 Base 22 10 1 0.6 3 0.8 0.3 0.3 20 20 60 2 Base 24 9 1 0.6 2 0.8 0.3 0.3 38 17 45 3 Base 23 9 2.2 1 10 1 0.3 0.5 30 10 50 4 Base 28 0 0 0 3 0 0 0 10 0 90 5 Base 28 1 0 0.3 3 0.2 0 0 22 0 78

(43) The table above shows that it is not the individual content of each element, but an effect of the content of each of the elements which is decisive in the presence or absence of the -Ni, -Ni.sub.3Al and -NiAl phases, and the relative proportion of each of them.