CN107937874A - A kind of method for preparing Pt Al high-temperature protection coatings on niobium alloy surface - Google Patents

Abstract

The invention discloses a method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy. Dry and set aside; (2) put the niobium alloy substrate treated in step (1) into an ion sputtering device to prepare the Pt layer; (3) prepare the niobium alloy containing the Pt layer prepared in step (2) After the substrate is embedded and infiltrated with Al, a Pt-Al high-temperature protective coating is prepared on the surface of the niobium alloy. The Al element content in the Pt-Al high temperature protective coating is 60-70wt%, the Pt element content is 2-8wt%, and the Nb element content is 20-30wt%. The Pt-Al high-temperature protective coating prepared by the present invention is continuous, dense and smooth, and is metallurgically bonded to the niobium alloy substrate. The bonding strength is high, and the preparation process is a vacuum ion sputtering method, which is different from the traditional electroplating method, and has the advantages of simple operation and energy saving. The advantages.

Description

A method for preparing Pt-Al high temperature protective coating on the surface of niobium alloy

technical field

The invention relates to the technical field of high-temperature coating protection, in particular to a method for preparing a Pt-Al high-temperature protection coating on the surface of a niobium alloy.

Background technique

With the development of high thrust-to-weight ratio aero-engines, the operating environment of their turbine blades is more harsh, which puts forward higher requirements on the performance of blade materials. Niobium has a high melting point, moderate density, high specific strength at high temperature, excellent high temperature mechanical properties and processing properties, and is considered one of the important candidate materials for high temperature structural materials. However, niobium has poor oxidation resistance and forms "pest" oxidation at 600°C, which greatly limits its application. According to relevant research reports, coating a protective coating on the surface of niobium alloys can effectively improve the high-temperature oxidation resistance of niobium alloys, and can also take into account its high-temperature mechanical properties, and the coating protection method is easy to implement and has a significant effect, so it is widely used use.

Aluminide coating is currently the most commonly used coating, which mainly relies on the combination of aluminum and oxygen at high temperature to form a dense aluminum oxide film to block the diffusion of oxygen, thereby improving the oxidation resistance of the material. However, the high-temperature mechanical properties of a single aluminide coating are poor, and the resistance to thermal shock and external force is weak, and the coating will fail under load. Platinum-modified aluminide coatings have been proven to improve the bonding force between the Al ₂ O ₃ film and the substrate, enhance the structural stability of the coating, and inhibit the outward diffusion of elements. Platinum can improve the selective formation of oxide film, and can quickly form a new oxide layer after the oxide film falls off, that is, it has a self-healing function. The doping of platinum can reduce the internal stress of the oxide film to a certain extent and improve the adhesion of the oxide film. In addition, the presence of platinum also reduces the enrichment of S elements, so that the interface between the metal layer and the oxide layer loses the possibility of generating holes. It has also been reported that platinum reduces the rate at which matrix elements diffuse into the coating, thereby reducing the formation of harmful oxides. A number of research results show that, compared with other modified aluminide coatings, the high-temperature oxidation resistance of platinum-modified aluminide coatings is much better than other coatings. Related application documents such as: (1) Chinese invention patent, a single-phase platinum-modified aluminide coating and its preparation process, application number 20141061091.1; (2) Chinese invention patent, a nano-platinum-aluminum oxidation resistance for superalloys Coating preparation method, application number 200810058933.0; (3) Chinese invention patent, a protective coating for single crystal superalloy and its preparation method, application number 201310509194.3, etc.

The preparation methods of the platinum layer mainly include: (1) Metallurgical processing of composite platinum, which is to prepare composite platinum by rolling, drawing, extrusion and other methods. The material composite interface prepared by this method has high bonding strength, continuous and non-porous platinum layer, and controllable thickness, but it is difficult to prepare a platinum layer below 10 μm, and it is even more difficult to process workpieces with complex shapes. (2) The platinum layer is prepared by the electroplating method, and the metal ions in the electroplating solution are reduced and deposited on the cathode (workpiece) by an external current to form platinum metal, including molten salt electroplating and aqueous solution electroplating. The molten salt platinum plating process is complicated, the operating environment is poor, and the cost is high; aqueous solution electroplating is currently a more economical and practical method to obtain a platinum layer. The disadvantage is that the required plating solution formula is complex and produces more industrial wastewater.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a Pt-Al high-temperature protective coating with low energy consumption, easy operation, continuous and dense coating, good combination with the substrate, and effective improvement of the high-temperature oxidation resistance of niobium alloys. Coating method.

The technical scheme of the present invention is: a method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy, comprising the following steps:

(1) Pre-treat the surface of the niobium alloy substrate, polish it with 240#, 400#, 600#, 800#, 1000# and 1500# sandpaper in sequence, clean it with acetone ultrasonically, rinse it with deionized water, and dry it spare;

(2) Put the niobium alloy substrate treated in step (1) into the ion sputtering apparatus to prepare the Pt layer; the target is a pt target, the distance from the target to the niobium alloy substrate table is 20-30mm, and the vacuuming rate is 20-25I/min, the sputtering vacuum is 5-15Pa, the current is 45-48mA, the sputtering time is 2-5min, and a Pt layer with a thickness of 8-12nm is prepared on the surface of the niobium alloy substrate;

(3) The niobium alloy substrate containing the Pt layer prepared by step (2) is subjected to Al embedding treatment; firstly, the niobium alloy substrate containing the Pt layer is sealed into a crucible filled with aluminizing agent, and then the crucible is placed Put it into a vacuum tube furnace, vacuumize and raise the temperature to 300-350°C for 1-2 hours, then continue to heat up to 900-1000°C, keep it for 4-6 hours, then cool to room temperature with the vacuum tube furnace, and prepare Pt- on the surface of the niobium alloy. Al high temperature protective coating.

Further, the purity of the Pt target in the step (1) is 99.9-99.999%.

Further, the composition of the aluminizing agent in the step (3) is 5-12% by weight of Al powder, 1-5% of NaF powder, and the balance is Al ₂ O ₃ powder, and the above three powders are mixed Made by ball milling for 1 to 5 hours.

Further, the thickness of the Pt-Al high-temperature protective coating is 60-75 μm, the Al element content in the Pt-Al high-temperature protective coating is 60-70wt%, the Pt element content is 2-8wt%, and the Nb element content is 20 ~30wt%.

The beneficial effects of the present invention are:

1. The Pt layer preparation process adopted in the present invention is a vacuum ion sputtering method, which is different from the traditional electroplating method. It has the advantages of easy operation and energy saving, greatly shortens the preparation time of the Pt layer, and the ion sputtering instrument has Ultra-low discharge voltage, the current does not need to pass through the sample, the temperature rise is small, and the sample damage is weakened.

2. The Pt-Al high-temperature protective coating prepared by the present invention is continuous, dense and smooth, and is metallurgically bonded to the niobium alloy substrate, with high bonding strength.

3. Compared with the single aluminide coating, the oxidation resistance of the Pt-Al high temperature protective coating obtained in the present invention is greatly improved at the same temperature.

Description of drawings

Fig. 1 is a cross-sectional morphology diagram of the Pt-Al high temperature protective coating prepared in Example 1 of the present invention.

Fig. 2 is a comparison chart of high temperature oxidation weight gain of the Pt-Al high temperature protective coating prepared in Example 1 of the present invention and the single aluminized coating.

Fig. 3 is the XRD spectrum of the Pt-Al high temperature protective coating prepared in Example 1 of the present invention before and after oxidation.

Fig. 4 is a surface morphology diagram after oxidation of the Pt-Al high temperature protective coating prepared in Example 1 of the present invention.

Fig. 5 is a cross-sectional morphology diagram after oxidation of the Pt-Al high temperature protective coating prepared in Example 1 of the present invention.

Reference numerals: 1—electroless Ni plating protective layer, 2—Pt—Al high temperature protective coating, 3—C103 niobium alloy substrate, 4—oxidation product.

Detailed ways

Example 1

A method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy, comprising the following steps:

1. Select C103 niobium alloy as the substrate, and its chemical composition is shown in the table below

Element f Ti Zr W Ta Nb Content wt (%) 10.0 1.30 0.34 0.31 0.30 Bal.

Pre-treat the surface of the niobium alloy substrate, polish it with 240#, 400#, 600#, 800#, 1000# and 1500# sandpaper in sequence, clean it with acetone ultrasonically, rinse it with deionized water, and dry it for later use;

2. Put the niobium alloy substrate processed in step 1 into the MSP-1S ion sputtering apparatus to prepare the Pt layer; the target is a Pt target with a purity of 99.9-99.999%; the target is placed on the niobium alloy substrate platform The distance is 25mm, the vacuum rate is 20I/min, the sputtering vacuum is 10Pa, the current is 47mA, the sputtering time is 2min, and a Pt layer with a thickness of 8-12nm is prepared on the surface of the niobium alloy substrate;

3. The niobium alloy substrate containing the Pt layer prepared in step 2 is processed by embedding and infiltrating Al; first, the niobium alloy substrate containing the Pt layer is sealed into a crucible filled with an aluminizing agent, and the aluminizing agent composition is by weight The percentage is 10% Al powder, 3% NaF powder, and the balance is Al ₂ O ₃ powder. The above three powders are mixed and ball milled for 2 hours; then the crucible is placed in a vacuum tube furnace, vacuumed and heated Heat at 300°C for 1 hour, then continue to heat up to 940°C, hold for 4 hours, then cool to room temperature with a vacuum tube furnace, and prepare a Pt-Al high-temperature protective coating on the surface of the niobium alloy.

Example 2

1. Select C103 niobium alloy as the substrate, and its chemical composition is shown in the table below

Element f Ti Zr W Ta Nb Content wt (%) 10.0 1.30 0.34 0.31 0.30 Bal.

Pre-treat the surface of the niobium alloy substrate, polish it with 240#, 400#, 600#, 800#, 1000# and 1500# sandpaper in sequence, clean it with acetone ultrasonically, rinse it with deionized water, and dry it for later use;

2. Put the niobium alloy substrate processed in step 1 into the MSP-1S ion sputtering apparatus to prepare the Pt layer; the target is a Pt target with a purity of 99.9-99.999%; the target is placed on the niobium alloy substrate platform The distance is 25mm, the vacuum rate is 20I/min, the sputtering vacuum is 10Pa, the current is 47mA, the sputtering time is 2min, and a Pt layer with a thickness of 8-12nm is prepared on the surface of the niobium alloy substrate;

3. The niobium alloy substrate containing the Pt layer prepared in step 2 is processed by embedding and infiltrating Al; first, the niobium alloy substrate containing the Pt layer is sealed into a crucible filled with an aluminizing agent, and the aluminizing agent composition is by weight The percentage is 10% Al powder, 5% NaF powder, and the balance is Al ₂ O ₃ powder. The above three powders are mixed and ball milled for 2 hours; then the crucible is placed in a vacuum tube furnace, vacuumed and heated Heat at 300°C for 1 hour, then continue to heat up to 940°C, hold for 4 hours, then cool to room temperature with a vacuum tube furnace, and prepare a Pt-Al high-temperature protective coating on the surface of the niobium alloy.

Example 3

1. Select C103 niobium alloy as the substrate, and its chemical composition is shown in the table below

Element f Ti Zr W Ta Nb Content wt (%) 10.0 1.30 0.34 0.31 0.30 Bal.

Pre-treat the surface of the niobium alloy substrate, polish it with 240#, 400#, 600#, 800#, 1000# and 1500# sandpaper in sequence, clean it with acetone ultrasonically, rinse it with deionized water, and dry it for later use;

2. Put the niobium alloy substrate processed in step 1 into the MSP-1S ion sputtering apparatus to prepare the Pt layer; the target is a Pt target with a purity of 99.9-99.999%; the target is placed on the niobium alloy substrate platform The distance is 25mm, the vacuum rate is 20I/min, the sputtering vacuum is 10Pa, the current is 47mA, the sputtering time is 2min, and a Pt layer with a thickness of 8-12nm is prepared on the surface of the niobium alloy substrate;

3. The niobium alloy substrate containing the Pt layer prepared in step 2 is processed by embedding and infiltrating Al; first, the niobium alloy substrate containing the Pt layer is sealed into a crucible filled with an aluminizing agent, and the aluminizing agent composition is by weight The percentage is 10% Al powder, 5% NaF powder, and the balance is Al ₂ O ₃ powder. The above three powders are mixed and ball milled for 2 hours; then the crucible is placed in a vacuum tube furnace, vacuumed and heated Heat at 300°C for 1 hour, then continue to heat up to 1000°C, hold for 4 hours, then cool to room temperature with a vacuum tube furnace, and prepare a Pt-Al high-temperature protective coating on the surface of the niobium alloy.

The phase structure of the coating was detected by X-ray diffraction, and the cross-sectional morphology of the coating was observed by scanning electron microscopy (SEM). When preparing the cross-section sample, a Ni layer was electrolessly plated on the surface of the sample in advance to protect the coating morphology of the cross-section sample.

As shown in Figure 1, the Pt-Al high-temperature protective coating prepared in Example 1 is continuous and dense, and is well bonded to the C103 niobium alloy substrate, without defects such as cracks and holes; it is found by EDS that the content of Al in the coating is 64.96 wt%, the Nb content is 22.34wt%, and the Pt content is 3.56 wt%.

As a comparative reference, the difference between the preparation method of the Al coating on the surface of the C103 niobium alloy substrate and that of Example 1 is that there is no step 2. The Pt-Al high-temperature protective coating prepared in Example 1 and the monopermeable Al coating on the surface of the niobium alloy substrate were respectively subjected to high-temperature oxidation experiments in a resistance furnace. The experimental temperature was 1100 ° C, and the experimental time was 100 hours. , 2h, 5h, 10h, 20h, 30h, 50h and 100h, weigh the mass of the sample and record it.

As shown in Figure 2, the quality growth of the Pt-Al coating and the single-aluminized coating was relatively flat before 20 hours of oxidation, and the single-aluminized coating began to be rapidly oxidized after 20 hours, and the slope of the quality change curve changed. large, the Pt-Al coating oxidizes slowly before 30h, and the oxidation resistance after 30h is also significantly increased compared with the single aluminized coating; in contrast, the Pt-Al coating prepared in Example 1 has a negative effect on the C103 niobium alloy substrate It has better high temperature protection.

As shown in Figure 3, the Pt-Al high-temperature protective coating prepared in Example 1 is composed of _two phases, Al ₃ Nb and PtAl ₂ . It diffuses outwards and combines with Al elements deposited on the surface to form Al ₃ Nb phase. After oxidation, Al ₂ O ₃ and part of Nb ₂ O ₅ phases are formed on the coating surface. As shown in Figure 2, compared with the single aluminized coating, the presence of Pt element makes the Al element easy to diffuse to a certain extent, promotes the formation of the Al ₂ O ₃ film layer, and improves the self-healing ability of the Al ₂ O ₃ film , improve the oxidation resistance of the coating. As the oxidation progresses, the PtAl ₂ phase is gradually consumed, and the Al ₂ O ₃ film gradually falls off, and the Nb element in the matrix combines with O to form the Nb ₂ O ₅ phase.

As shown in Figure 4 and Figure 5, after the Pt-Al high temperature protective coating prepared in Example 1 is oxidized, flocculent oxidation products are formed on the surface. According to EDS detection, the O element content is 35.64wt%, and the Al element content is 41.02 wt%, Nb element content is 8.10wt%, combined with the analysis of XRD detection results in Figure 3, it can be obtained that the oxidation products are Al ₂ O ₃ and Nb ₂ O ₅ . After oxidation, the inner layer of the coating is still dense and continuous, without cracks and holes, and the bonding is good.

The above is only a specific implementation of the present invention, but the scope of protection of the present invention is not limited thereto, and any changes or simple replacements that do not go through creative work should be covered within the scope of protection of the present invention.

Claims (4)

1. A method for preparing a Pt-Al high-temperature protective coating on the niobium alloy surface, is characterized in that, comprises the following steps: (1) Pre-treat the surface of the niobium alloy substrate, polish it with 240#, 400#, 600#, 800#, 1000# and 1500# sandpaper in sequence, clean it with acetone ultrasonically, rinse it with deionized water, and dry it spare; (2) Put the niobium alloy substrate treated in step (1) into the ion sputtering apparatus to prepare the Pt layer; the target is a pt target, the distance from the target to the niobium alloy substrate table is 20-30mm, and the vacuuming rate is 20-25I/min, the sputtering vacuum is 5-15Pa, the current is 45-48mA, the sputtering time is 2-5min, and a Pt layer with a thickness of 8-12nm is prepared on the surface of the niobium alloy substrate; (3) The niobium alloy substrate containing the Pt layer prepared by step (2) is subjected to Al embedding treatment; firstly, the niobium alloy substrate containing the Pt layer is sealed into a crucible filled with aluminizing agent, and then the crucible is placed Put it into a vacuum tube furnace, evacuate and heat up to 300-350°C for 1-2 hours, then continue to heat up to 900-1000°C, keep it for 4-6 hours, then cool to room temperature with the vacuum tube furnace, and prepare Pt- on the surface of niobium alloy. Al high temperature protective coating. 2. The method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy according to claim 1, characterized in that: the purity of the Pt target in the step (1) is 99.9-99.999%. 3. The method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy according to claim 1, characterized in that: the aluminizing agent composition in the step (3) is 5-12% Al by weight percentage powder, 1-5% NaF powder, and the balance Al ₂ O ₃ powder. The above three powders are mixed and milled for 1-5 hours. 4. The method for preparing a Pt-Al high-temperature protective coating on the surface of a niobium alloy according to claim 1, characterized in that: the thickness of the Pt-Al high-temperature protective coating is 60 to 75 μm, and the Pt-Al high-temperature protective coating The Al element content in the layer is 60-70wt%, the Pt element content is 2-8wt%, and the Nb element content is 20-30wt%.