Ti3sic2 modified silicide coating and method of making

Abstract

The application discloses a Ti3SiC2 modified silicide coating and a preparation method thereof, and belongs to the technical field of high-temperature alloy thermal protection. In the application, the base material of Nb-based ultrahigh-temperature alloy and mixed coating powder obtained by mixing, ball-milling and obtaining Ti3SiC2 powder, Nb powder and Si powder are loaded into a mold together, and are pressure-sintered in a discharge plasma sintering furnace, and then are cooled to obtain the Ti3SiC2 modified silicide coating-Ti3SiC2 / NbSi2. The Ti3SiC2 modified silicide coating has better toughness, fewer cracks, stronger oxidation resistance and longer working life at high temperature. The Ti3SiC2 modified silicide coating prepared by the above method has more excellent high-temperature oxidation resistance than the silicide coating without Ti3SiC2. After being oxidized at 1200 DEG C for 50 hours, the coating sample is dense and complete, and has no peeling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature alloy thermal protection, in particular to a Ti3SiC2 modified silicide coating and a preparation method thereof. BACKGROUND

[0002] Nb-based ultrahigh-temperature alloy is an important candidate for high-temperature structural materials of future aero-engines due to its high melting point, moderate density, excellent high-temperature mechanical properties and other advantages. However, the poor oxidation resistance and the spalling of the oxide film at high temperature limit its application in the aviation field. It is difficult to meet the development requirements of aero-engines by relying on process improvement of the material itself, so the preparation of high-temperature protective coating on its surface is a key technology to promote the engineering application of the alloy.

[0003] Silicide coating has high melting point, good thermal stability, can form SiO2 at high temperature oxidation, and has good self-healing ability, so it is widely used in the high-temperature protection of Nb-based alloys. However, silicide is highly brittle (the fracture toughness of NbSi2 is only 2.5-3 MPa·m 1 / 2 ), and microcracks are easily generated, which generates a large internal stress inside when oxidized, resulting in cracking and even spalling of the coating and its oxide film. Yue et al. found that the WSi2 barrier layer in the MoSi2 / WSi2 / NbSi2 composite coating can effectively delay the outward diffusion of alloying elements, reduce the oxidation rate of the coating, and inhibit the interdiffusion between the coating and the substrate. However, the microcracks in the NbSi2 inner layer provide a fast channel for the invasion of oxygen, causing the continuous accumulation of oxides near the cracks, which eventually leads to the cracking and spalling of the coating. In recent years, the addition of modifying elements and their synergistic addition have played a key role in improving the fluidity of the oxide film on the surface of the coating and the adhesion between the oxide film and the coating, and have achieved certain results. However, the brittleness of the coating itself has not been fundamentally changed, and the problem of easy generation of microcracks has not been effectively solved, which limits the service life of the coating. Therefore, the present application provides a Ti3SiC2 modified silicide coating and a preparation method thereof. SUMMARY

[0004] The present application provides a Ti3SiC2 modified silicide coating and a preparation method thereof, which effectively solves the technical problems of poor inherent toughness and insufficient oxidation resistance of single silicide coating, and provides a Ti3SiC2 modified silicide coating with simple process, convenient operation, dense structure and mechanical strength.

[0005] The present application provides a preparation method of a Ti3SiC2 modified silicide coating, characterized in that it comprises the following steps:

[0006] S1, mixing, ball-milling Ti3SiC2 powder, Nb powder and Si powder to obtain mixed coating powder;

[0007] S2, cutting, grinding, cleaning Nb-based super high temperature alloy to obtain base material;

[0008] S2, loading the base material and the mixed coating powder in a mold and pressurizing sintering in a discharge plasma sintering furnace, and cooling to obtain Ti3SiC2 modified silicide coating.

[0009] Preferably, in S1, the mass ratio of Ti3SiC2 powder in the mixed coating powder is 4.07% to 76.33%, the mass ratio of Nb powder is 14.75% to 59.78%, and the mass ratio of Si powder is 8.92% to 36.15%.

[0010] Preferably, the atomic ratio of Nb to Si in the Nb powder and Si powder is 1:2.

[0011] Preferably, in S1, the ball-milling speed is 100 to 400 r / min, and the ball-milling time is 4 to 8 h.

[0012] Preferably, in S2, the first layer of mixed coating powder is laid on the bottom of the mold, and then the base material is placed, and then the second layer of mixed coating powder is laid on the base material.

[0013] Preferably, the base material is a round piece with a diameter of 10 mm and a thickness of 4 mm, and the mass ratio of the first layer of mixed coating powder to the second layer of mixed coating powder is 1:1.

[0014] Preferably, in S2, the sintering temperature is 1300 to 1450℃, the holding time is 5 to 10 min, and the pressure is 25 to 35 MPa.

[0015] Preferably, in S1, the base material is obtained by using electric spark wire cutting Nb-based super high temperature alloy, polishing with SiC sandpaper, and cleaning in an ultrasonic cleaning machine with anhydrous ethanol.

[0016] The application also provides a Ti3SiC2 modified silicide coating prepared by the above preparation method.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] (1) The application packs the matrix material of the Nb-based ultrahigh-temperature alloy and mixed coating powder obtained by mixing, ball milling Ti3SiC2 powder, Nb powder and Si powder into a mold, and sintering under pressure in a spark plasma sintering furnace, and then cooling to obtain a Ti3SiC2 modified silicide coating-Ti3SiC2 / NbSi2. The silicide coating modified by Ti3SiC2 is better in toughness, less in cracks, stronger in oxidation resistance, and longer in working life at high temperature. The Ti3SiC2 modified silicide coating prepared by the above method is more excellent in high-temperature oxidation resistance than the silicide coating without Ti3SiC2, and the coating sample is dense and complete without peeling after 1200℃ oxidation for 50h.

[0019] (2) The oxidation weight gain of the Ti3SiC2 modified silicide coating prepared in Example 1 of the application is 7.94mg / cm 2 , and the oxidation weight gain of the Nb-based ultrahigh-temperature alloy in Comparative Example 1 and the unmodified silicide coating in Comparative Example 2 is 420.10mg / cm 2 and 185.09mg / cm 2 , respectively.

[0020] (3) The preparation process of the Ti3SiC2 modified silicide coating provided by the application is simple and convenient to operate, the prepared coating has dense structure and good performance, and is suitable for promotion and application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the technical roadmap of the Ti3SiC2 modified silicide coating of the application;

[0022] Figure 2 is the macroscopic morphology diagram of the Ti3SiC2 modified silicide coating on the surface of the Nb-based ultrahigh-temperature alloy in Example 1 of the application;

[0023] Figure 3 is the X-ray diffraction spectrum of the Ti3SiC2 modified silicide coating in Example 1 of the application;

[0024] Figure 4 is the cross-sectional morphology diagram of the Ti3SiC2 modified silicide coating on the surface of the Nb-based ultrahigh-temperature alloy in Example 1 of the application;

[0025] Figure 5 is the macroscopic morphology diagram of the Ti3SiC2 modified silicide coating prepared in Example 2 of the application after 1200℃ oxidation for 50h;

[0026] Figure 6 is the macroscopic morphology diagram of the unmodified silicide coating prepared in Comparative Example 2 of the application after 1200℃ oxidation for 50h;

[0027] Figure 7This is a macroscopic morphology image of the comparative example 1Nb-based superalloy of the present invention after oxidation at 1200℃ for 50 hours;

[0028] Figure 8 This is a graph showing the oxidative weight gain of the samples from Example 2, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0030] Example 1

[0031] This invention provides a method for preparing a Ti3SiC2 modified silicide coating, comprising the following steps:

[0032] (1) Preparation of matrix: Nb-based super high temperature alloy is cut into circular pieces with a size of Φ10mm×4mm by wire electrical discharge cutting, and polished smooth with SiC sandpaper of 80~800#. Then, it is cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then taken out and dried for later use.

[0033] (2) Preparation of coating powder: Accurately weigh 25.6% Ti3SiC2 powder, 46.3% Nb powder and 28.1% Si powder by mass percentage as coating material. Here, the volume ratio of Ti3SiC2 powder is 30%, the volume ratio of Nb powder and Si powder mixture is 70%, and the atomic ratio of Nb to Si is 1:2.

[0034] (3) Ball milling of coating powder: The prepared coating powder is ball milled and mixed using a ball mill at a speed of 400 r / min for 8 h.

[0035] (4) Mold assembly: Spread 0.8g of coating powder evenly on the bottom of the graphite mold, then place the prepared substrate in the center of the powder, and finally add 0.8g of coating powder into the mold to cover the substrate, and compact it with a graphite press head. Place a graphite foil between the press head and the powder to isolate the coating powder. Then wrap the sides of the mold with black graphite felt;

[0036] (5) Sintering: Install the mold in the discharge plasma sintering furnace, first evacuate the vacuum, and then start sintering. The sintering process uses infrared temperature measurement. The sintering temperature is 1350℃, and the holding time is 10min. The pressure is 35MPa. After sintering, turn off the power and let the furnace cool.

[0037] (6) Sampling: After the cooling is complete, the mold is taken out of the furnace cavity, the sample is pressed out with a universal testing machine, the coating condition is checked and the coating surface is cleaned with sandpaper to remove the surface graphite carbon paper, and finally Ti3SiC2 modified silicide coating is obtained.

[0038] The macroscopic morphology of the obtained Ti3SiC2 modified silicide coating is as follows: Figure 2 As shown, the X-ray diffraction pattern is as follows: Figure 3 As shown. The Ti3SiC2 modified silicide coating was cut in half along its diameter using wire electrical discharge machining (EDM). Metallographic mounting was performed using resin powder. The cross-section of the mounted sample was polished with 400-2000# SiC sandpaper and then polished with 1.5μm diamond polishing paste. The prepared sample was ultrasonically cleaned in anhydrous ethanol for 15 min and then dried with a hair dryer. Scanning electron microscopy analysis was performed, and the cross-sectional morphology of the obtained Ti3SiC2 modified silicide coating is shown in the figure. Figure 4 As shown, the Ti3SiC2 modified silicide coating has fewer cracks and a denser microstructure.

[0039] Example 2

[0040] This invention provides a method for preparing a Ti3SiC2 modified silicide coating, comprising the following steps:

[0041] (1) Preparation of matrix: Nb-based super high temperature alloy is cut into circular pieces with a size of Φ10mm×4mm by wire electrical discharge cutting, and polished smooth with SiC sandpaper of 80~800#. Then, it is cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then taken out and dried for later use.

[0042] (2) Preparation of coating powder: Accurately weigh 44.6% Ti3SiC2 powder, 34.5% Nb powder and 20.9% Si powder by mass percentage as coating material. Here, the volume ratio of Ti3SiC2 powder is 50%, the volume ratio of Nb powder and Si powder mixture is 50%, and the atomic ratio of Nb to Si is 1:2.

[0043] (3) Ball milling of coating powder: The prepared coating powder is ball milled and mixed using a ball mill at a speed of 400 r / min for 8 h.

[0044] (4) Mold assembly: Spread 0.8g of coating powder evenly on the bottom of the graphite mold, then place the prepared substrate in the center of the powder, and finally add 0.8g of coating powder into the mold to cover the substrate, and compact it with a graphite press head. Place a graphite foil between the press head and the powder to isolate the coating powder. Then wrap the sides of the mold with black graphite felt;

[0045] (5) Sintering: The mold is installed in the discharge plasma sintering furnace. First, a vacuum is drawn, and then sintering begins. Infrared temperature measurement is used during the sintering process. The sintering temperature is 1400℃, the holding time is 5min, and the pressure is 30MPa. After sintering, the power is turned off and the furnace is cooled.

[0046] (6) Sampling: After the temperature has cooled down, remove the mold from the furnace cavity and press out the sample using a universal testing machine;

[0047] (7) Cleaning: Inspect the coating condition and clean the coating surface with sandpaper, peel off the surface graphite carbon paper, and finally obtain the Ti3SiC2 modified silicide coating.

[0048] (8) Oxidation: The antioxidant performance was tested by using a high-temperature box furnace, and the oxidation was carried out at 1200℃ for 50h.

[0049] The macroscopic morphology of the obtained Ti3SiC2 modified silicide coating after oxidation is as follows: Figure 5 As shown, the coating is dense and intact, with no obvious peeling.

[0050] Example 3

[0051] This invention provides a method for preparing a Ti3SiC2 modified silicide coating, comprising the following steps:

[0052] (1) Preparation of matrix: Nb-based super high temperature alloy is cut into circular pieces with a size of Φ10mm×4mm by wire electrical discharge cutting, and polished smooth with SiC sandpaper of 80~800#. Then, it is cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then taken out and dried for later use.

[0053] (2) Preparation of coating powder: Accurately weigh 4.07% Ti3SiC2 powder, 59.78% Nb powder and 36.15% Si powder by mass percentage as coating material. Here, the volume percentage of Ti3SiC2 powder is 5%, the volume percentage of the mixture of Nb powder and Si powder is 95%, and the atomic ratio of Nb to Si is 1:2.

[0054] (3) Ball milling of coating powder: The prepared coating powder is ball milled and mixed using a ball mill at a speed of 400 r / min for 8 h.

[0055] (4) Mold assembly: Spread 0.8g of coating powder evenly on the bottom of the graphite mold, then place the prepared substrate in the center of the powder, and finally add 0.8g of coating powder into the mold to cover the substrate, and compact it with a graphite press head. Place a graphite foil between the press head and the powder to isolate the coating powder. Then wrap the sides of the mold with black graphite felt;

[0056] (5) Sintering: Install the mold in the discharge plasma sintering furnace, first evacuate the vacuum, and then start sintering. Infrared temperature measurement is used during the sintering process. The sintering temperature is 1300℃, and the holding time is 5 minutes. The pressure is 30MPa. After sintering, turn off the power and let the furnace cool.

[0057] (6) Sampling: After the cooling is complete, the mold is taken out of the furnace cavity, the sample is pressed out with a universal testing machine, the coating condition is checked and the coating surface is cleaned with sandpaper to remove the surface graphite carbon paper, and finally Ti3SiC2 modified silicide coating is obtained.

[0058] Example 4

[0059] This invention provides a method for preparing a Ti3SiC2 modified silicide coating, comprising the following steps:

[0060] (1) Preparation of matrix: Nb-based super high temperature alloy is cut into circular pieces with a size of Φ10mm×4mm by wire electrical discharge cutting, and polished smooth with SiC sandpaper of 80~800#. Then, it is cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then taken out and dried for later use.

[0061] (2) Preparation of coating powder: Accurately weigh 76.33% Ti3SiC2 powder, 14.75% Nb powder and 8.92% Si powder by mass percentage as coating material. Here, the volume ratio of Ti3SiC2 powder is 80%, the volume ratio of Nb powder and Si powder mixture is 20%, and the atomic ratio of Nb to Si is 1:2.

[0062] (3) Ball milling of coating powder: The prepared coating powder is ball milled and mixed using a ball mill at a speed of 400 r / min for 8 h.

[0063] (4) Mold assembly: Spread 0.8g of coating powder evenly on the bottom of the graphite mold, then place the prepared substrate in the center of the powder, and finally add 0.8g of coating powder into the mold to cover the substrate, and compact it with a graphite press head. Place a graphite foil between the press head and the powder to isolate the coating powder. Then wrap the sides of the mold with black graphite felt;

[0064] (5) Sintering: Install the mold in the discharge plasma sintering furnace, first draw a vacuum, and then start sintering. The sintering process uses infrared temperature measurement. The sintering temperature is 1450℃, and the holding time is 5 minutes. The pressure is 25MPa. After sintering, turn off the power and let the furnace cool.

[0065] (6) Sampling: After cooling, the mold is taken out of the furnace cavity, the sample is pressed out with a universal testing machine, the coating condition is checked and the coating surface is cleaned with sandpaper to remove the surface graphite carbon paper, and finally Ti3SiC2 modified silicide coating is obtained.

[0066] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows:

[0067] Comparative Example 1

[0068] A method for preparing a silicide coating includes the following steps:

[0069] (1) Preparation of matrix: Nb-based super high temperature alloy is cut into circular pieces with a size of Φ10mm×4mm by wire electrical discharge cutting, and polished smooth with SiC sandpaper of 80~800#. Then, it is cleaned with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, and then taken out and dried for later use.

[0070] (2) Preparation of coating powder: Accurately weigh 62.3% Nb powder and 37.7% Si powder by mass percentage as coating material, with the atomic ratio of Nb to Si being 1:2.

[0071] (3) Ball milling of coating powder: The prepared coating powder is ball milled and mixed using a ball mill at a speed of 400 r / min for 8 h.

[0072] (4) Mold assembly: Spread 0.8g of coating powder evenly on the bottom of the graphite mold, then place the prepared substrate in the center of the powder, and finally add 0.8g of coating powder into the mold to cover the substrate, and compact it with a graphite press head. Place a graphite foil between the press head and the powder to isolate the coating powder. Then wrap the sides of the mold with black graphite felt;

[0073] (5) Sintering: Install the mold in the discharge plasma sintering furnace, first draw a vacuum, and then start sintering. The sintering process uses infrared temperature measurement, the sintering temperature is 1400℃, the holding time is 5min, the pressure is 30MPa, after sintering is completed, the power is turned off and the furnace is cooled.

[0074] (6) Sampling: After the temperature has cooled down, remove the mold from the furnace cavity and press out the sample using a universal testing machine;

[0075] (7) Cleaning: Inspect the coating condition and clean the coating surface with sandpaper, peel off the surface graphite carbon paper, and finally obtain the unmodified siliconized coating.

[0076] (8) Oxidation: The antioxidant performance was tested by using a high-temperature box furnace, and the oxidation was carried out at 1200℃ for 50h.

[0077] The macroscopic morphology of the obtained unmodified silicide coating after oxidation is as follows: Figure 6 As shown (as) Figure 5 (Comparative test) The coating was oxidized into powder.

[0078] Comparative Example 2

[0079] (1) Sample preparation: The Nb-based super-high temperature alloy (C-103Nb alloy) was cut into block samples with dimensions of 8mm×8mm×4mm by wire electrical discharge machining.

[0080] (2) Polishing and cleaning: First, polish with 80-1000# SiC sandpaper to make it smooth, then clean with anhydrous ethanol in an ultrasonic cleaner for 10 minutes, take it out and blow it dry for later use.

[0081] (3) Weighing: Weighing was performed using an analytical balance with an accuracy of 0.1 mg;

[0082] (4) Oxidation test: The antioxidant performance was tested by using a high-temperature box furnace and oxidized at 1200℃ for 50h.

[0083] The macroscopic morphology of the obtained matrix after oxidation is as follows Figure 7 As shown. (For) Figure 5 and Figure 6 (Comparative test) The Ti3SiC2 modified silicide coating prepared in Example 2 of this invention has better high-temperature oxidation resistance than the silicide coating without Ti3SiC2. After oxidation at 1200℃ for 50h, the coating sample is dense and intact, with no peeling.

[0084] The oxidation weight gain diagrams of the samples prepared in Example 2, Comparative Example 1, and Comparative Example 2 of this invention are shown below. Figure 8 As shown, the oxidative weight gain of the Ti3SiC2 modified silicide coating prepared in Example 2 was 7.94 mg / cm³. 2 The oxidation weight gain of the Nb-based superalloy in Comparative Example 2 and the unmodified silicide coating in Comparative Example 1 reached 420.10 mg / cm³, respectively. 2 and 185.09 mg / cm 2 .

[0085] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a Ti3SiC2 modified silicide coating, characterized in that, Includes the following steps: S1, Ti3SiC2 powder, Nb powder and Si powder are mixed and ball-milled to obtain a mixed coating powder; the mass percentage of Ti3SiC2 powder in the mixed coating powder is 4.07%~76.33%, the mass percentage of Nb powder is 14.75%~59.78%, and the mass percentage of Si powder is 8.92%~36.15%; the atomic ratio of Nb to Si in the Nb powder and Si powder is 1:2; The Nb-based superalloy was cut, ground, and cleaned to obtain the matrix material. S2, the matrix material and mixed coating powder of S1 are loaded into a mold and sintered under pressure in a spark plasma sintering furnace, and then cooled to obtain a Ti3SiC2 modified silicide coating; the sintering temperature is 1300~1450℃, the holding time is 5~10min, and the pressure is 25~35MPa.

2. The preparation method according to claim 1, characterized in that, In S1, the ball milling speed is 100~400 r / min, and the ball milling time is 4~8 h.

3. The preparation method according to claim 1, characterized in that, In S2, a first layer of the mixed coating powder is laid at the bottom of the mold, then the base material is placed on it, and a second layer of the mixed coating powder is laid on the base material.

4. The preparation method according to claim 3, characterized in that, The substrate material is a circular sheet with a diameter of 10 mm and a thickness of 4 mm. The mass ratio of the first layer of mixed coating powder to the second layer of mixed coating powder is 1:

1.

5. The preparation method according to claim 1, characterized in that, In S1, the matrix material is obtained by wire cutting an Nb-based ultra-high temperature alloy with electrical discharge machining, polishing it smooth with SiC sandpaper, and cleaning it with anhydrous ethanol in an ultrasonic cleaner.

6. A Ti3SiC2 modified silicide coating prepared by the preparation method according to any one of claims 1 to 5.

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