CN106148907B - High temperature resistance protective coating and its preparation of high-temperature alloy base mechanics performance are not influenced - Google Patents

Abstract

The present invention provides a high temperature resistant protective coating that utilizes autothermal dynamics reaction to automatically generate a Cr ₂₃ C _{6 ceramic} diffusion barrier in _situ . MCrAlX surface layer composition, where M is Ni and/or Co, X is at least one of Hf, Si, Zr, rare earth elements and mixed rare earth elements, and the rare earth elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd , Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; mixed rare earths are two or more rare earth elements used at the same time; the content of Cr in the surface layer of MCrAlX is 25% to 40%, and the content of Al is 5% to 15%, X content is 0.05% to 1.5%. The coating has good anti-stripping performance, and can significantly reduce the occurrence of Al in the coating diffusing to the substrate, preventing the mechanical degradation of the substrate caused by interdiffusion.

Description

High temperature resistant protective coating without affecting the mechanical properties of superalloy matrix and its preparation

technical field

The invention belongs to the field of metal high-temperature protection, and particularly provides a high-temperature-resistant protective coating that does not affect the mechanical properties of a high-temperature alloy matrix and a preparation method thereof.

Background technique

Many parts work in high temperature environment, such as gas turbine blades and so on. Coating high temperature resistant protective coating on the surface of parts can improve the service life of parts and avoid early damage.

Commonly used high-temperature protective coatings are MCrAlY (where M=Ni, Co or a combination thereof) and aluminized coatings. When the working temperature is lower than 1000°C, the above-mentioned coating can provide good high-temperature protection performance without affecting the mechanical properties of the matrix. However, under higher working temperature conditions, the interdiffusion between the coating and the substrate is too fast, and a large amount of Al in the coating diffuses to the substrate. On the one hand, the coating will effectively resist the loss of high-temperature alloy components and reduce the life of the coating. , on the other hand, it will form a secondary reaction zone at the coating/substrate interface, and acicular topological close-packed phases will appear, which seriously affects the mechanical properties of the substrate, and can reduce the creep life of the substrate by up to 80%.

In order to avoid coating/substrate interdiffusion without affecting the mechanical properties of the substrate, researchers have developed a high-temperature resistant coating technology with a diffusion barrier, that is, before depositing a conventional high-temperature resistant coating, a thin diffusion-resistant layer is pre-deposited. Diffusion barrier materials that have been developed include refractory metals (such as Re, Mo, etc.), ceramics (such as TiN, Al2O3, etc.). The refractory metal diffusion barrier has good anti-stripping performance, but insufficient diffusion resistance, while the ceramic diffusion barrier has good diffusion resistance, but is easy to peel off in the process of cooling and heating cycles. In addition, the fabrication process of the diffusion barrier increases the coating cost.

The reason why the ceramic diffusion barrier has good anti-diffusion performance is that the diffusion rate of anti-oxidation component Al in ceramics is low, and the solid solubility of Al in ceramics other than alumina is low. In other words, the extremely low solid solubility of Al in the ceramic diffusion barrier, or the extremely slow migration rate, can play a role in hindering the diffusion of Al in the coating to the substrate through the ceramic layer. There are two main reasons for the poor anti-stripping performance of ceramic diffusion barriers: the artificially prepared interface has insufficient bonding force, and the thermal expansion coefficient of ceramics is quite different from that of superalloys and MCrAlY coatings. When the thermal stress exceeds the interfacial bonding force, cracking occurs at the interface, which in turn causes the coating to peel off.

In order to meet the two requirements of anti-stripping performance and good diffusion resistance performance, it is necessary to develop a new diffusion-resistant high-temperature protective coating technology. To solve the problem of anti-stripping performance of ceramic diffusion barriers, we should mainly start from improving the interface bonding force, because it is difficult to control the thermal expansion coefficient of ceramics.

Contents of the invention

The invention provides a high-temperature-resistant protective coating technology for automatically generating a Cr ₂₃ C ₆ ceramic diffusion barrier in situ by using a self-heating dynamic reaction.

Concrete invention scheme is as follows:

A high-temperature resistant protective coating that does not affect the mechanical properties of a high-temperature alloy matrix is characterized in that:

The high temperature resistant protective coating is composed of Cr ₂₃ C ₆ phase intermediate layer (Cr ₂₃ C ₆ diffusion barrier layer formed spontaneously in situ) and MCrAlX surface layer;

The MCrAlX surface layer, wherein M is Ni and/or Co, X is at least one of Hf, Si, Zr, rare earth elements and mixed rare earth elements, and the rare earth elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; mixed rare earths are two or more of the above rare earth elements used simultaneously;

In the MCrAlX surface layer, the Cr content is 25wt%-40wt%, the Al content is 5wt%-15wt%, the X content is 0.05wt%-1.5wt%, and the M is the rest.

The thickness of the Cr ₂₃ C ₆ phase intermediate layer is 0.1 μm to 10 μm;

The thickness of the MCrAlX surface layer is 10 μm-1000 μm; the grain size is less than 100 nm.

Superalloys usually contain a small amount of C, which can form fine carbides at the grain boundaries with metals such as Cr, Mo, and W, thereby improving the creep properties of the alloy. Prepare a nanocrystalline MCrAlX surface layer with a Cr content that reaches a certain threshold (beyond the solid solubility of the parent phase) on the surface of a superalloy with a C content that reaches a certain threshold (enough to form carbides). Using the high diffusivity of nanocrystals, the coating can / interface forms a Cr ₂₃ C ₆ diffusion barrier. If the C content of the superalloy is too low, such as less than 0.01wt%, a layer of superalloy layer can be prepared first to increase the C content to 0.2wt% to 0.4wt%, so as to ensure that there is enough C under the MCrAlX surface layer. It can be used to form Cr ₂₃ C ₆ diffusion barrier. The solid solubility of Al in Cr ₂₃ C ₆ is extremely low, so Cr ₂₃ C ₆ can hinder the diffusion of Al and prevent the Al in the coating from diffusing into the matrix. The bonding force of in-situ formed Cr ₂₃ C ₆ to the coating and the substrate is significantly higher than that of the Cr ₂₃ C ₆ layer prepared by the coating method, so it has good anti-stripping performance.

The high-temperature protective coating of the present invention is characterized in that a ceramic layer with low thermal conductivity can be added on the surface of the MCrAlX surface layer, and its thickness is 30 μm to 1000 μm. The low thermal conductivity ceramic layer is preferably ZrO ₂ -xY ₂ O ₃ , Nd ₂ Zr ₂ O ₇ , Nd ₂ Zr ₂ O ₇ /ZrO ₂ -xY ₂ O ₃ , wherein ZrO ₂ -xY ₂ O ₃ is the bottom layer, Nd ₂ Zr ₂ O ₇ is the surface layer, x=6mol%～8mol%.

The preparation method of the high temperature resistant protective coating of the present invention is characterized in that:

The preparation equipment is: magnetron sputtering apparatus;

The preparation process is: (1), casting and processing the MCrAlX target; (2), adjusting the C content of the superalloy substrate target to 0.2wt% to 0.4wt%, casting and processing the superalloy substrate target; (3) 1. Using high-temperature alloy substrate target material, sputtering deposition of 5 μm ~ 10 μm coating; (4), using MCrAlX target material, sputtering deposition of 10 μm ~ 1000 μm MCrAlX coating; (5), 900 ℃ ~ 1000 ℃ for parts Vacuum annealing, the time is 1h ~ 2h.

For superalloy parts with a C content higher than 0.2wt%, processes (2) and (3) can be omitted, that is, casting and processing of superalloy substrate targets and deposition of superalloy layers are not required;

For superalloy parts whose working temperature is higher than 900°C, the process (5) can be omitted, that is, the vacuum annealing process is not required;

During the preparation process, the temperature of the vacuum chamber should be controlled within the range of 150°C to 290°C.

The process (5) can be replaced by the following process: use electron beam physical vapor deposition, plasma spraying or chemical vapor deposition to deposit a low thermal conductivity ceramic layer, and the heating temperature of the parts is 900°C to 1080°C.

The chemical composition of the MCrAlX target in the process (1) is preferably Co 19wt%-23wt%, Cr 25wt%-27wt%, Al 9wt%-11wt%, Y 0.1wt%-0.5wt%, Hf 0.05wt%-0.5 wt%, Si 0.1wt% ~ 0.9wt%, the sum of Y, Hf, Si content is not more than 1.5wt%, Ni is the balance.

The present invention adopts the magnetron sputtering method to deposit the MCrAlX surface layer on the superalloy substrate. During the vacuum annealing or service process, the Cr in the MCrAlX surface layer and the C in the substrate undergo an interfacial reaction to form a Cr ₂₃ C ₆ interphase The middle layer is a diffusion barrier layer, which can significantly reduce the occurrence of Al in the coating to diffuse into the substrate, thereby preventing the mechanical degradation of the substrate caused by interdiffusion. The high temperature resistant protective coating has good peeling resistance.

Description of drawings

Figure 1 Schematic diagram of the coating architecture.

Figure 2 is the cross-sectional morphology of the NiCrAlYSiHf coating deposited by magnetron sputtering on the surface of the nickel-based superalloy K417G, after 100 cycles of 1000°C heat preservation for 5 min-water quenching test.

Figure 3 is the NiCrAlYSiHf coating deposited by magnetron sputtering on the surface of the nickel-based superalloy K417G, and the element surface distribution of the cross-sectional electron probe oxidized at 1000°C for 40h. Region III is the Cr ₂₃ C ₆ diffusion barrier formed in situ.

Detailed ways

Example 1

Vacuum smelting casting target material Ni-25Cr-10Al-0.5Y-0.5Si-0.5Hf (wt.%), processed into a flat target; using magnetron sputtering method to deposit NiCrAlYSiHf coating on the surface of nickel-based superalloy K417G parts, coating The layer thickness is about 30μm, and the grain size is less than 20nm; vacuum annealing is carried out at 1000℃×2h. Carry out a water quenching test on the coated parts (1000°C for a sufficient time to heat the parts thoroughly; then put the parts into deionized water, the water temperature is 15°C to 35°C, and the water volume is sufficient so that the temperature rise of the parts does not exceed 30°C; when the temperature of the parts is the same as that of the water, take out the parts and dry them with dry hot air for 1 cycle). After 100 cycles of testing, the surface coating of the parts did not crack or peel off. An anatomical analysis of the parts revealed that the coating/substrate interface formed a dense and firmly bonded Cr ₂₃ C ₆ diffusion barrier during the annealing process, and there was no cracking during the test, as shown in Figure 2.

Example 2

The preparation method is the same as in Example 1. Oxidation test (1000°C×40h) was carried out on the coated parts. An anatomical analysis of the parts revealed that the dense and firmly bonded Cr ₂₃ C ₆ diffusion barrier formed at the coating/substrate interface during the annealing process did not crack during the test. A Cr-poor region appears in the coating near the diffusion barrier, as shown in Figure 3, indicating that the formation mechanism of the diffusion barrier is: Cr in the coating diffuses to the coating/substrate interface, and forms Cr ₂₃ C ₆ with C in the substrate. Floor. The Al content in the Cr ₂₃ C ₆ layer is extremely low, indicating that it is difficult for Al to pass through the diffusion barrier.

Example 3

Vacuum melting cast coating target material Ni-30Cr-6Al-0.4Y-0.1Ce-0.1Dy (wt.%), processed into a flat target; vacuum melting casting alloy target material Ni-10Co-9Cr-7W-5Al-0.1Ti -0.3C (wt.%), processed into a flat target; use magnetron sputtering method to deposit Ni-10Co-9Cr-7W on the surface of nickel-based superalloy Ni-10Co-9Cr-7W-5Al-0.1Ti-0.01C parts -5Al-0.1Ti-0.3C nanocrystalline layer with a thickness of 5 μm and a grain size of less than 20 nm; then deposit a nanocrystalline NiCrAlYCeDy coating with a thickness of about 30 μm and a grain size of less than 20 nm by magnetron sputtering. Conduct oxidation test at 1000℃×300h. An anatomical analysis of the parts revealed that the dense and firmly bonded Cr ₂₃ C ₆ diffusion barrier formed at the coating/substrate interface during the annealing process did not crack during the test. The Al content in the Cr ₂₃ C ₆ layer is extremely low, indicating that it is difficult for Al to pass through the diffusion barrier.

Example 4

On the basis of the coating preparation in Example 3, the ZrO ₂ -7Y ₂ O ₃ coating was prepared by EB-PVD (Electron Beam Physical Vapor Deposition), the preparation temperature was 980°C, and the thickness of the ZrO ₂ -7Y ₂ O ₃ layer was 150 μm. Carry out the thermal shock resistance test of the parts (use the plasma flame to blow the parts to coat the coated surface, and use compressed air to blow the uncoated back of the parts, the maximum temperature of the hot side is 1050 ℃, and the maximum temperature of the cold side is 800 ℃; 5min, stop for 5min as a cycle). After 1000 cycles of testing, the coating did not peel off. An anatomical analysis of the parts revealed that the dense and firmly bonded Cr ₂₃ C ₆ diffusion barrier formed at the coating/substrate interface during the annealing process did not crack during the test. The Al content in the Cr ₂₃ C ₆ layer is extremely low, indicating that it is difficult for Al to pass through the diffusion barrier.

Example 5

The preparation method is the same as in Example 1. An oxidation test (1000°C×100h) was carried out on the coated sample, followed by a durability performance test (the test temperature was 760°C, and the test stress was 645MPa). Compared with the low-pressure plasma sprayed NiCrAlY coating sample, the oxidation test and endurance life test of the same test parameters were carried out. The test results show that the durable life data of the 5 samples coated with this coating are: 189h, 193h, 221h, 225h, 240h; the durable life data of the 5 samples coated with the comparative coating are: 49h, 83h, 131h, 135h, 140h. In contrast, the average life of the sample coated with this coating (213.6h) is basically the same as that of the uncoated sample (~220h), and it is about twice as long as that of the sample coated with the comparative coating (107.6h) .

Example 6

Vacuum melting casting target material Ni-21Co-25Cr-10Al-0.5Y (wt.%), processed into a flat target; NiCoCrAlY coating was deposited on the surface of nickel-based superalloy K417G parts by magnetron sputtering, and the coating thickness was about 10 μm , the grain size is less than 20nm; vacuum annealing is carried out at 1000℃×2h. Using the same method as in Example 1 to carry out the water quenching test for 100 cycles, no cracking or peeling of the part surface coating occurred.

Example 7

Co-30Cr-7Al-0.1Dy (wt.%) casting target material was vacuum smelted and processed into a planar target; a CoCrAlDy coating was deposited on the surface of nickel-based superalloy K417G parts by magnetron sputtering. The coating thickness was about 10 μm, and the crystal The particle size is less than 15nm; vacuum annealing is carried out at 1000℃×2h. Using the same method as in Example 1 to carry out the water quenching test for 100 cycles, no cracking or peeling of the part surface coating occurred.

Example 8

Vacuum melting and casting targets A and B, wherein the chemical composition of target A is Ni-0.3C-10Co-8.9Cr-7W-2Mo-5.3Al-0.8Ti-3.8Ta-1.5Hf-0.015B (wt.%) , the chemical composition of the B target is Ni-20Co-25Cr-10Al-0.3Y-0.2Hf-0.5Si (wt.%), which is processed into a planar target. Using the magnetron sputtering method, the above-mentioned targets A and B are sequentially used to deposit layers A and B on the surface of the directionally solidified nickel-based superalloy DZ125 part, and the coating thicknesses are about 8 μm and about 40 μm, respectively. Then use the EB-PVD (Electron Beam Physical Vapor Deposition) method to deposit ZrO ₂ -xY ₂ O ₃ and Nd ₂ Zr ₂ O ₇ layers in sequence, the preparation temperature is 980 ° C, and the thickness of the ZrO ₂ -xY ₂ O ₃ layer is 30 μm , x=6mol%, and the thickness of the Nd ₂ Zr ₂ O ₇ layer is 120 μm. An anatomical analysis of the part revealed that the layer A/layer B interface formed a dense and firmly bonded Cr ₂₃ C ₆ diffusion barrier. The Al content in the Cr ₂₃ C ₆ layer is extremely low, indicating that it is difficult for Al to pass through the diffusion barrier. Carry out the thermal shock resistance test of the parts (use the plasma flame to blow the parts to coat the coated surface, and use compressed air to blow the uncoated back of the parts, the maximum temperature of the hot side is 1050 ℃, and the maximum temperature of the cold side is 800 ℃; 5min, stop for 5min as a cycle). After 1000 cycles of testing, the coating did not peel off.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A high temperature resistant protective coating that does not affect the mechanical properties of a superalloy substrate, characterized in that: The high temperature resistant protective coating is composed of Cr ₂₃ C ₆ phase intermediate layer and MCrAlX surface layer; The MCrAlX surface layer, wherein M is Ni and/or Co, X is at least one of Hf, Si, Zr, rare earth elements and mixed rare earth elements, and the rare earth elements are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y; mixed rare earths are two or more of the above rare earth elements used simultaneously; In the MCrAlX surface layer, the content of Cr is 25wt%-40wt%, the content of Al is 5wt%-15wt%, and the content of X is 0.05wt%-1.5wt%. 2. According to the described high temperature resistant protective coating of claim 1, it is characterized in that: The thickness of the Cr ₂₃ C ₆ phase intermediate layer is 0.1 μm to 10 μm; The thickness of the MCrAlX surface layer is 10 μm to 1000 μm; The grain size of the MCrAlX surface layer is less than 100nm. 3. The high temperature resistant protective coating according to claim 1, characterized in that: a ceramic layer with low thermal conductivity is added on the surface of the MCrAlX surface layer, the thickness of which is 30 μm-1000 μm. 4. The high temperature resistant protective coating according to claim 3, characterized in that: the low thermal conductivity ceramic layer is ZrO ₂ -xY ₂ O ₃ , Nd ₂ Zr ₂ O ₇ , Nd ₂ Zr ₂ O ₇ /ZrO ₂ -xY ₂ O ₃ , wherein ZrO ₂ -xY ₂ O ₃ is the bottom layer, Nd ₂ Zr ₂ O ₇ is the surface layer, x=6mol%～8mol%. 5. a preparation method of the described high temperature resistant protective coating of claim 1, is characterized in that: The preparation equipment is: magnetron sputtering apparatus; The preparation process is: (1), casting and processing the MCrAlX target material; (2), adjusting the C content of the superalloy matrix target material to 0.2wt% to 0.4wt%, casting and processing the superalloy matrix target material; (3) 1. Using high-temperature alloy substrate target material, sputtering deposition of 5 μm ~ 10 μm coating; (4), using MCrAlX target material, sputtering deposition of 10 μm ~ 1000 μm MCrAlX coating; (5), 900 ℃ ~ 1000 ℃ for parts Vacuum annealing, the time is 1h ~ 2h. 6. according to the preparation method of the described high temperature resistant protective coating of claim 5, it is characterized in that: for the superalloy parts with C content higher than 0.2wt%, omit the process (2) and (3) described in claim 5 . 7. The preparation method of the high temperature resistant protective coating according to claim 5, characterized in that: for superalloy parts with working temperature higher than 900°C, the process (5) of claim 5 is omitted. 8. The method for preparing the high temperature resistant protective coating according to claim 5, characterized in that: the temperature of the vacuum chamber in the process (3) and (4) is controlled within the range of 150°C to 290°C. 9. according to the preparation method of the described high-temperature protective coating of claim 5, it is characterized in that: process (5) can be replaced by following process: adopt electron beam physical vapor deposition, plasma spraying or chemical vapor deposition method, deposition Low thermal conductivity ceramic layer, the heating temperature of parts is 900℃～1080℃. 10. According to the preparation method of the high temperature resistant protective coating according to claim 5, it is characterized in that: the chemical composition of the MCrAlX target is Co 19wt%-23wt%, Cr 25wt%-27wt%, Al 9wt%-11wt% , Y 0.1wt% ~ 0.5wt%, Hf 0.05wt% ~ 0.5wt%, Si 0.1wt% ~ 0.9wt%, the sum of Y, Hf, Si content is not more than 1.5wt%, Ni is the balance.