High-temperature aluminizing protection coating and aluminizing protection method for tenon with air entraining hole

Abstract

The invention discloses a high-temperature aluminizing protection coating and an aluminizing protection method for a tenon with air entraining holes, the high-temperature aluminizing protection coating is used for tenon aluminizing protection, and comprises a first coating coated on the surface of a substrate and a second coating coated on the surface of the first coating; the first coating comprises a first coating, and the raw materials of the first coating comprise metal powder Ni, Cr, Al and a binder; the second coating comprises a second coating, raw materials of the second coating comprise metal powder Ni, Cr, Al and a binder, and the dosage of the metal powder Al in the first coating is smaller than that of the metal powder Al in the second coating. The aluminized protective coating can provide effective protection for the non-aluminized part of the high-temperature aluminized blade at the temperature of 1080 DEG C, the protected non-aluminized surface is free of leakage, the protection success rate is 100%, and platinum-aluminized tenon protection of aero-engine blades of multiple types has been widely used.

Description

Technical Field

[0001] The invention relates to the technical field of aeroengine and gas turbine manufacturing, and in particular to a high-temperature aluminizing protective coating and a tenon aluminizing protective method with air ducting holes. Background Art

[0002] With the development of modern aviation industry, the operating temperature of gas turbines is getting higher and higher. In order to meet the use requirements of gas turbines in high temperature, high speed and strong corrosive environment, gas turbine blades began to use aluminizing process. After the tenon is aluminized, it will cause notch sensitivity and easy to crack. Therefore, the tenon part cannot be aluminized and needs protection. The aluminizing temperature of aluminized parts can reach 1080℃ or higher, and the insulation time is as long as 6h. The protection of non-aluminized surface during high temperature and long-term aluminizing becomes a major problem.

[0003] In addition, in order to adapt to the increasing turbine temperature, the turbine blades of aircraft engines and gas turbines widely use internal cavity air film cooling technology, such as Figure 1 As shown, the cooling air enters the inner cavity of the blade from the tenon, and is discharged through the air film hole on the exhaust side to cool the blade; according to the use requirements of turbine blades, the blade body and air cooling channel require aluminum infiltration, and the tenon requires protection; if the protective cover method is used for protection, during the aluminum infiltration process, the aluminum infiltration atmosphere is easy to enter the tenon position through the exhaust hole and the tenon air inlet, resulting in protection failure; if the paint coating method is used, the paint is easy to flow into the inner cavity, resulting in the inner cavity requiring aluminum infiltration surface without a layer; at the same time, there is a risk that the residual paint in the inner cavity is difficult to clean, which will cause the parts to be scrapped in serious cases. Therefore, the tenon with an air inlet further increases the difficulty of high-temperature aluminum infiltration protection.

[0004] At present, the main protection schemes for non-aluminized parts of blades are: 1) Reserved margin method: After the overall aluminization, the aluminized layer is mechanically removed to achieve the purpose of no aluminized layer in this part. However, this method has the problem that the aluminized layer will crack due to the vibration of the machining process in the subsequent machining process, and the aluminized layer of the component is hard and brittle and is easily damaged, so the processing qualification rate of such parts in actual production is low. 2) Metal protective cover method: Li Ke et al. proposed in "Protection process of non-aluminized parts in gas phase aluminization of gas turbine blades" (Metal Processing-Hot Processing No. 23, 2012) to wrap the tenon with metal foil to achieve the purpose of non-aluminized surface protection. There is a good protective effect in the vapor phase aluminization of parts with no air inlet or small air inlet below 1000℃, but in the actual processing process, the metal foil is sintered on the surface of the substrate, which makes cleaning difficult, and in severe cases, the parts will be scrapped. In addition, it is difficult to ensure that the foil layer fits the parts well when wrapping parts with metal foil. During the high-temperature infiltration process, the metal foil will deform, causing the gap to further increase. The aluminizing atmosphere can easily enter the tenon part along the gap and through the exhaust hole and the tenon air inlet. In the vapor phase aluminizing below 1000℃, the tenon part protected by this method has a 0-5μm infiltration layer. In the platinum-aluminum infiltrated blades above 1000℃, the aluminizing layer of the tenon protected by this method is further deepened and has lost its protective effect.

[0005] Chinese patent CN107267912B discloses an aluminized protective coating, which is mainly suitable for solid powder embedding aluminization below 900°C. It is a protective coating made of metal nickel, zirconium oxide and a binder. It needs to be naturally dried for 6 to 24 hours after each coating, and the protection time is long. The protective effect is lost when it exceeds 1020°C, and high-temperature aluminization at a temperature of up to 1080°C cannot be used for non-aluminized surface protection. Chinese patent CN110923621A discloses an aluminum-chromium co-infiltrated protective coating, which uses metal nickel, metal chromium, metal aluminum and zirconium oxide as protective coatings for aluminum-chromium co-infiltrated non-infiltrated surface protection. The anti-seepage temperature can reach 1025 to 1080°C, but a single-component multi-layer coating is used for protection, and it is difficult to balance the anti-seepage effect and the ease of removal in terms of component ratio. Figure 2 As shown, after using this method for protection, some protective coating remains when the coating is removed and needs to be manually cleaned again; in addition, after the coating is applied, before entering the furnace for penetration, the strength of the protective layer coating is low, and it is very easy to be damaged during the subsequent sand blowing and hanging process before the parts enter the furnace. Summary of the invention

[0006] The invention provides a high-temperature aluminizing protective coating and a tenon aluminizing protective method with air duct holes, so as to solve the technical problems of poor protective effect, low strength of protective layer coating and easy residue in the existing protective coating.

[0007] According to one aspect of the present invention, a high-temperature aluminized protective coating is provided.

[0008] The high-temperature aluminizing protective coating is used for aluminizing protection, and comprises a first coating coated on the surface of a substrate and a second coating coated on the surface of the first coating;

[0009] The first coating layer comprises a first coating material, wherein the raw materials of the first coating material comprise metal powders Ni, Cr, Al and a binder;

[0010] The second coating layer comprises a second coating material, the raw materials of the second coating material comprise metal powders Ni, Cr, Al and a binder, and the amount of metal powder Al in the first coating material is less than the amount of metal powder Al in the second coating material.

[0011] Furthermore, the usage ratio of the metal powders Ni, Cr and Al in the first coating is 10-15:2-5:0.5-1.

[0012] Furthermore, the usage ratio of the metal powders Ni, Cr and Al in the second coating is 10-14:4-6:2-5.

[0013] Furthermore, the binder is a polyvinyl alcohol aqueous solution with a concentration of 5% to 15%.

[0014] Furthermore, the thickness of the first coating layer is 2-6 mm, and the thickness of the second coating layer is 3-6 mm.

[0015] Furthermore, the preparation method of the first coating and the second coating comprises the following steps:

[0016] The raw metal powders Ni, Cr and Al in the first coating are added to a ball mill and ground into a mixture, a binder is added to the mixture, and then ball milling is performed to obtain the first coating;

[0017] The raw metal powders Ni, Cr and Al in the second coating are added to a ball mill and crushed to obtain a mixture. A binder is added to the mixture, and then ball milling is performed to obtain the second coating.

[0018] According to another aspect of the present invention, there is also provided a method for protecting tenons from aluminum infiltration with air ducts, comprising the following steps:

[0019] S1: A protective piece is provided at the air inlet hole of the tenon to seal the air inlet hole;

[0020] S2: applying a first coating on the surface of the tenon, and curing the first coating to form a first coating;

[0021] S3: coating a second coating on the surface of the first coating on the tenon, and curing the second coating to form a second coating, so that the high-temperature aluminized protective coating is formed on the tenon;

[0022] S4: The parts with tenons are subjected to sandblasting and aluminizing treatment. After aluminizing, the parts are taken out and the coating on the tenons is knocked to peel off.

[0023] Furthermore, the method further comprises applying the first coating several times, and after each application, placing the tenon in an oven for baking to solidify the first coating;

[0024] The second coating is applied several times, and after each application, the tenon is placed in an oven to bake to cure the second coating.

[0025] Furthermore, the protective member is one of paper tape or nickel foil.

[0026] Furthermore, the method also includes finishing the paint on the parts and removing excess parts after completing the first coating or the second coating.

[0027] The present invention has the following beneficial effects:

[0028] 1) The high-temperature aluminized protective coating of the present invention is used for tenon aluminizing protection, including a first coating for coating on the tenon surface to form a first coating and a second coating for coating on the first coating surface to form a second coating. The raw materials of the first coating and the second coating are metal powder Ni, Cr, Al and a binder, and the amount of metal powder Al in the first coating is less than the amount of metal powder Al in the second coating. The first coating has the same composition as the second coating, has good thermal expansion coefficient and compatibility, and is not prone to stratification and peeling during the entire aluminizing process. Among them, metal Ni and Cr are used as sacrificial elements to form a continuous Ni and Cr powder coating layer on the tenon surface, so that they first react with Al in the aluminizing atmosphere to form a stable intermetallic compound, thereby preventing Al from quickly penetrating inward, and protecting the non-aluminized surface at high temperature. At the same time, Al can maintain a certain Al activity in the coating to prevent Al from expanding outward on the surface of the tenon substrate to form an Al-poor layer. In addition, the Al content in the first coating is lower than that in the second coating. When Al acts as a binder, there will not be too much excess to cause adhesion to the base metal, so that the coating is not easy to remain. The second coating has a high Al content. After the binder volatilizes at high temperature, the aluminum melts at high temperature and fills the gaps in the solid coating to form a tight protective coating, preventing the aluminizing atmosphere from entering the surface of the protected material substrate through the gaps, thereby improving the aluminizing protective effect.

[0029] 2) The aluminized protective coating obtained by using the high-temperature aluminized protective coating of the present invention can provide effective protection for the non-aluminized parts of the high-temperature aluminized blades at a temperature of 1080°C. There is no leakage on the non-aluminized surface after protection, and the protection success rate is 100%. It has been widely used for the protection of platinum-aluminum tenons of blades of multiple models of aircraft engines.

[0030] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be described in further detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 It is a cross-sectional view of the inner cavity of a gas turbine working blade with an air cooling channel;

[0033] Figure 2 This is a residual picture of the coating on the tenon after aluminizing in the prior art;

[0034] Figure 3 This is the high temperature aluminizing tenon protection flow chart;

[0035] Figure 4 Use paper tape to protect the tenon air intake holes;

[0036] Figure 5 The morphology diagram after the first coating is configured;

[0037] Figure 6 Applying a first coating and a second coating to the tenon and then modifying the topography;

[0038] Figure 7 This is a rendering of the protective coating peeling and removal effect;

[0039] Figure 8 This is the tenon morphology after coloring of the aluminized part. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0041] An embodiment of the first aspect of the present invention provides a high-temperature aluminized protective coating, wherein the high-temperature aluminized protective coating is used for aluminized protection, and comprises a first coating layer coated on a substrate surface and a second coating layer coated on a surface of the first coating layer;

[0042] The first coating layer comprises a first coating material, wherein the raw materials of the first coating material comprise metal powders Ni, Cr, Al and a binder;

[0043] The second coating layer comprises a second coating material, the raw materials of the second coating material comprise metal powders Ni, Cr, Al and a binder, and the amount of metal powder Al in the first coating material is less than the amount of metal powder Al in the second coating material.

[0044] The high-temperature aluminized protective coating of the present invention is used for tenon aluminizing protection, including a first coating for coating on the tenon surface to form a first coating and a second coating for coating on the first coating surface to form a second coating. The raw materials of the first coating and the second coating are metal powder Ni, Cr, Al and a binder, and the amount of metal powder Al in the first coating is less than the amount of metal powder Al in the second coating. The first coating has the same composition as the second coating, has good thermal expansion coefficient and compatibility, and is not prone to stratification and peeling during the entire aluminizing process. Among them, metal Ni and Cr are used as sacrificial elements to form a continuous Ni and Cr powder coating layer on the tenon surface, so that they first react with Al in the aluminizing atmosphere to form a stable intermetallic compound, thereby preventing Al from quickly penetrating inward, and protecting the non-aluminized surface at high temperature. At the same time, Al can maintain a certain Al activity in the coating to prevent Al from expanding outward on the surface of the tenon substrate to form an Al-poor layer. In addition, the Al content in the first coating is lower than that in the second coating. When Al acts as a binder, there will not be too much excess to cause adhesion to the base metal, so that the coating is not easy to remain. The second coating has a high Al content. After the binder volatilizes at high temperature, the aluminum melts at high temperature and fills the gaps in the solid coating to form a tight protective coating, preventing the aluminizing atmosphere from entering the surface of the protected material substrate through the gaps, thereby improving the aluminizing protective effect.

[0045] The high-temperature aluminizing protective coating of the present invention is a two-layer composite anti-seepage coating, wherein the first coating used to be coated on the surface of the tenon to form a first coating is in direct contact with the non-aluminizing surface, has the characteristics of not adhering to the substrate surface, low coating strength, and easy removal; the second coating used to be coated on the surface of the first coating to form a second coating mainly plays an effective shielding role, preventing the external aluminizing atmosphere from entering the non-aluminizing surface, and playing an anti-seepage role; at the same time, the anti-seepage coating inside the tenon is wrapped and protected to prevent the anti-seepage coating from being damaged during sandblasting and cleaning or hanging before the parts enter the furnace.

[0046] If only the first coating is used, after the binder evaporates at high temperature, only the solid phase skeleton component and molten aluminum are left as high-temperature binder. Due to the low aluminum content in the first coating, it cannot fill the solid phase gaps well at high temperature, cannot form a dense protective layer, and cannot achieve a complete anti-seepage effect.

[0047] If only the second coating is used, the aluminum content is high. In addition to filling the solid phase gaps in the coating at high temperatures, the excess aluminum has the risk of local point bonding with the base metal, making it difficult to remove the coating, and at the same time destroying the alloy composition of the base metal.

[0048] In the present invention, during the high-temperature aluminizing process, the parts are protected by aluminizing with a first coating layer and a second coating layer formed by a first coating layer and a second coating layer, so that the non-aluminized surface can be protected at a temperature of up to 1050°C to 1090°C, and the protective coating is effective in protecting the non-aluminized surface, easy to remove, does not corrode the substrate, and does not cause depletion of the substrate alloy elements; in addition, the protective layer has sufficient strength to ensure that it is not easily damaged during the subsequent sandblasting and mounting processes.

[0049] The raw materials of the first coating and the second coating are metal powders Ni, Cr, Al and binders. Compared with the protective coating disclosed in the prior art CN110923621A, zirconium oxide is lacking. Zirconium oxide is a ceramic powder and an inert filler. It is not easy to bond with molten aluminum at high temperature (metal is not welded with ceramic), and it is not easy to ensure the strength and density of the coating. Therefore, the coating raw materials of the present invention do not use non-metallic filler zirconium oxide, but can improve the strength and density of the coating. The protective coating described in the prior art CN110923621A is easy to cause damage to the protective coating under the pressure of 0.1MPa sand blasting, and requires additional protection. The protective coating of the present invention can withstand the sand blasting pressure of 0.3MPa, so the strength of the coating is higher.

[0050] At the same time, the present invention also replaces the binder from the water-insoluble nitrocellulose binder with a water-soluble polyvinyl alcohol binder, and the replaced binder has higher strength and better safety after film formation. Nitrocellulose has been listed in the "List of Dangerous Chemicals that Can Be Exploded and Prepared", which has the risk of being flammable and explosive and difficult to purchase, while polyvinyl alcohol is not a dangerous chemical.

[0051] In an embodiment of the present invention, the usage ratio of the metal powders Ni, Cr and Al in the first coating is 10-15:2-5:0.5-1.

[0052] Preferably, the amount ratio of the metal powder Ni, Cr, and Al in the first coating is 12:4:1 or 10:3:0.5 or 15:5:1 or 14:4:0.7, or any combination of 10-15:2-5:0.5-1. The amount ratio of the metal powder Ni, Cr, and Al in the first coating is 10-15:2-5:0.5-1. Under this ratio, the presence of aluminum can prevent the protective coating from disintegrating due to the absence of the binder and leaving only solid nickel and chromium after the binder evaporates. At the same time, the aluminum content is lower than that of the second coating, so there will not be too much excess when it acts as a binder, causing the first coating to adhere to the base metal, thereby making it difficult to remove the coating.

[0053] In an embodiment of the present invention, the usage ratio of the metal powders Ni, Cr and Al in the second coating is 10-14:4-6:2-5.

[0054] Preferably, the amount ratio of the metal powder Ni, Cr, and Al in the second coating is 12:5:3 or 10:4:3 or 11:5:2 or 14:6:5, or any combination of 10-14:4-6:2-5. The amount ratio of the metal powder Ni, Cr, and Al in the second coating is 10-14:4-6:2-5. The aluminum content in the second coating is relatively high. At high temperature, after the binder volatilizes, the aluminum melts at high temperature and fills the gaps in the solid coating to form a tight protective coating, thereby preventing the aluminum-infiltrated atmosphere from entering the surface of the substrate of the protected material through the gaps.

[0055] In an embodiment of the present invention, the binder is a polyvinyl alcohol aqueous solution. Furthermore, the concentration of the polyvinyl alcohol aqueous solution is 5% to 15%. Preferably, the concentration of the polyvinyl alcohol aqueous solution is any one of 5%, 7%, 9%, 10%, 12%, and 15%. The present invention uses a polyvinyl alcohol aqueous solution as a binder, which has moderate bonding strength and is easy to remove after aluminizing without residue. The adhesive has high viscosity and is not easy to stratify after mixing with metal powder, thereby ensuring the uniformity of the coating. During configuration, the coating and the binder are mixed in a volume ratio of 0.8 to 1.2:0.8 to 1.2. Preferably, the coating and the binder are mixed in a volume ratio of 1:1.

[0056] Polyvinyl alcohol is a water-soluble solvent with high viscosity. Only about 10% is needed to meet the coating adhesion requirements. It is easy to form a uniform film on the surface of the base metal. At the same time, polyvinyl alcohol will decompose at above 200°C. After high-temperature aluminization, polyvinyl alcohol has been completely decomposed, so the paint after high-temperature aluminization loses its adhesion, making the paint easy to remove without residue.

[0057] According to an embodiment of the second aspect of the present invention, there is also provided a method for preparing a first coating and a second coating, comprising the following steps:

[0058] The raw metal powders Ni, Cr and Al in the first coating are added to a ball mill and ground into a mixture, a binder is added to the mixture, and then ball milling is performed to obtain the first coating;

[0059] The raw metal powders Ni, Cr and Al in the second coating are added to a ball mill and crushed to obtain a mixture. A binder is added to the mixture, and then ball milling is performed to obtain the second coating.

[0060] In the present invention, the first coating and the second coating are prepared separately. When preparing the first coating or the second coating, metal powders Ni, Cr, and Al are added to a ball mill in proportion and ball milled for 0.5-3 hours, and then a binder is added to the mixture in proportion, and ball milling is continued for 0.5-3 hours to obtain a protective coating.

[0061] According to an embodiment of the third aspect of the present invention, there is also provided a method for protecting aluminizing a tenon with air duct holes, comprising the following steps (see Figure 3 ):

[0062] S1: Set a protective piece at the air inlet hole of the tenon to seal the air inlet hole (see Figure 4 );

[0063] S2: applying a first coating on the surface of the tenon, and curing the first coating to form a first coating;

[0064] S3: coating a second coating on the surface of the first coating on the tenon, and curing the second coating to form a second coating, so that the high-temperature aluminized protective coating is formed on the tenon;

[0065] S4: The parts with tenons are subjected to sandblasting and aluminizing treatment. After aluminizing, the parts are taken out and the coating on the tenons is knocked to peel off.

[0066] In step S1, before the protective coating is applied, a protective piece is used to seal the air inlet of the tenon to seal the air inlet, and then the protective coating is applied to prevent the anti-seepage coating from entering the inner cavity from the tenon. Furthermore, the protective piece is one of a paper tape or a nickel foil, and preferably, the protective piece is a paper tape. The paper tape will carbonize at high temperatures. After sectioning and analysis, it was found that the paper tape did not affect the matrix components. When the protective coating is used to protect the tenon with an air inlet, if the tenon is directly coated, the coating can easily enter the inner cavity, resulting in the inner cavity requiring aluminization without a layer, and even the coating remains in the inner cavity and cannot be removed, resulting in the scrapping of the parts. In the patent literature of non-aluminized surface protective coatings, most of them only disclose anti-seepage methods for non-aluminized surfaces, and do not provide specific implementation plans for aluminizing tenons with air inlets. The present invention solves the problem of aluminizing tenons with air inlets by using cheap paper tape to stick on the tenon air inlet.

[0067] In step S2, the first coating is applied several times, preferably 2-3 times, and after each application, the tenon is placed in an oven at 80°C to 120°C for 30°C to 120 minutes to cure the first coating, so that the thickness of the first coating is 2-6 mm;

[0068] In step S3, the second coating is applied several times, preferably 2-3 times. After each application, the tenon is placed in an oven at 80°C to 120°C and dried for 30°C to 120 minutes to solidify the second coating, so that the thickness of the second coating is 3-6 mm.

[0069] In the present invention, the protective coating needs to be applied multiple times so that the first coating and the second coating form a certain thickness. The multi-layer coating prevents the uneven single-layer coating from causing insufficient local thickness and improves the anti-seepage and isolation effects. If the thickness of the first coating is insufficient, the second coating is easy to penetrate into the first coating, resulting in difficulty in removing the coating after aluminizing. After each coating, the parts are placed in an oven for drying, so that the water in the polyvinyl alcohol aqueous solution can be volatilized to form a film, thereby ensuring the strength of the protective coating before entering the furnace for aluminizing.

[0070] It also includes finishing the coating on the parts after the first coating or the second coating is completed, removing the first coating and the second coating remaining on the surface to be aluminized (such as the blade body); finishing the protective coating around the aluminized and non-aluminized surfaces, exposing part of the metal matrix in the transition zone and removing the excess part. After the coated parts are cleaned, they are put into the furnace for aluminizing. After the aluminizing is completed, the protective coating is removed by knocking or squeezing. If some protective coating remains, it is cleaned with a soft brush or compressed air.

[0071] The present invention adopts cheap and readily available paper tape to seal the tenon air inlet hole (such as Figure 5 As shown in the figure), the tenon protective coating is then applied to solve the non-aluminized surface protection problem of the tenon blade with air inlet hole. The protective effect is good, and there is no leakage near the air inlet hole and residual protective coating in the inner cavity; the inner layer of the protective coating is easy to remove and clean. After the aluminizing is completed, the coating is crushed and broken by force, and the coating is separated from the substrate without residue (as shown in the figure). Figure 8 shown).

[0072] The following examples describe the present disclosure in more detail, and these examples are intended for illustrative purposes only.

[0073] Example 1

[0074] This embodiment provides a high-temperature aluminized protective coating, which is used for tenon aluminized protection, including a first coating for coating on the tenon surface to form a first coating and a second coating for coating on the surface of the first coating to form a second coating, wherein the amount ratio of metal powder Ni, Cr, and Al in the first coating is 12:4:1, the binder is a 5% polyvinyl alcohol aqueous solution, and the amount ratio of metal powder to binder is 1:1;

[0075] The amount ratio of the metal powders Ni, Cr and Al in the second coating is 12:5:3, the binder is a 12% polyvinyl alcohol aqueous solution, and the amount ratio of the metal powder to the binder is 1:1.

[0076] The preparation method of the protective coating comprises the following steps: adding metal powders Ni, Cr and Al into a ball mill in proportion and milling them for 1 hour, then adding a binder into the mixture in proportion and continuing milling for 1 hour to obtain the protective coating.

[0077] Example 2

[0078] The only difference between this embodiment and embodiment 1 is that the usage ratio of the metal powders Ni, Cr, and Al in the first coating in embodiment 1 is 10:3:0.5; and the usage ratio of the metal powders Ni, Cr, and Al in the second coating is 10:4:3.

[0079] Example 3

[0080] The only difference between this embodiment and embodiment 1 is that the usage ratio of the metal powders Ni, Cr, and Al in the first coating in embodiment 1 is 15:5:1; and the usage ratio of the metal powders Ni, Cr, and Al in the second coating is 11:5:2.

[0081] Example 4

[0082] The only difference between this embodiment and embodiment 1 is that the usage ratio of the metal powders Ni, Cr, and Al in the first coating in embodiment 1 is 14:4:0.7; and the usage ratio of the metal powders Ni, Cr, and Al in the second coating is 14:6:5.

[0083] Example 5

[0084] The only difference between this embodiment and embodiment 2 is that the binder in the first coating in embodiment 2 is a 9% polyvinyl alcohol aqueous solution; and the binder in the second coating is a 15% polyvinyl alcohol aqueous solution.

[0085] Example 6

[0086] The only difference between this embodiment and embodiment 3 is that the binder in the first coating in embodiment 3 is a 10% polyvinyl alcohol aqueous solution; and the binder in the second coating is a 14% polyvinyl alcohol aqueous solution.

[0087] Example 7

[0088] The only difference between this embodiment and Embodiment 1 is that in the raw materials of the first coating and the second coating in Embodiment 1, the usage ratio of the metal powder to the binder is 0.8:1.

[0089] Example 8

[0090] The only difference between this embodiment and Embodiment 2 is that in the raw materials of the first coating and the second coating in Embodiment 2, the usage ratio of the metal powder to the binder is 1:1.2.

[0091] The protective coatings in Examples 1-8 were used for tenon aluminum infiltration protection, with good anti-seepage effect and no residue, and a protection success rate of 100%.

[0092] Example 9

[0093] This embodiment provides a method for protecting tenons from aluminum infiltration with air duct holes, comprising the following steps:

[0094] S1: Use paper tape to seal the air inlet hole at the tenon, see Figure 4 ;

[0095] S2: Prepare the first coating according to the raw material ratio in Example 1. After the metal powder is prepared, it is ball-milled for 1 hour. After the solid-liquid mixture is mixed, it is ball-milled for another 1 hour. The ball-milled first coating is applied to the surface of the tenon to be protected, with a thickness of 1mm to 2mm / layer. After the coating is completed, the part is placed in an oven at 85°C and baked for 30 minutes. After the previous layer of coating is completely cured, the next layer is applied. After coating, it is dried. A total of 2 layers are applied to form the first coating. See Figure 5 ;

[0096] After the first coating is applied and dried, remove the remaining coating that has flowed or accidentally applied to the surface that needs to be aluminized (such as the blade body);

[0097] S3: Prepare the coating according to the proportion of Example 1, ball-mill the solid powder for 1 hour after preparation, and ball-mill for another 1 hour after solid-liquid mixing, and apply the ball-milled coating on the tenon surface coated with the first coating, with a thickness of 1 mm to 2 mm per layer. After coating, place the workpiece with the tenon facing upward in an oven at 85° C. and bake for 30 minutes until the previous layer of coating is completely cured, and then apply the next layer. After coating, dry the coating, and apply a total of 3 layers to form a second coating;

[0098] After the second coating is dried, remove the residual coating that has flowed or accidentally applied to the surface that needs to be aluminized (such as the blade body); finish the protective coating in the transition area between the aluminized surface and the non-aluminized surface to expose part of the metal matrix in the transition area, see Figure 6 ;

[0099] S4: According to the requirements of aluminizing the parts, the aluminizing surface of the protected parts is sandblasted, and after sandblasting, the parts are placed in a vapor phase aluminizing furnace for aluminizing. The aluminizing temperature is 1080°C and the aluminizing holding time is 6 hours.

[0100] After aluminizing, take out the parts and tap the tenon protective layer with a mallet. The protective coating will peel off and there will be no coating residue. Figure 7 .

[0101] The aluminized parts of Example 9 were subjected to overall sandblasting. After sandblasting, the parts were placed in an air box furnace for color treatment at 580°C for 1 hour. After color treatment, the aluminized surface was yellow and the tenon part was blue, indicating that there was no aluminized layer on the tenon and the protection was effective. Figure 8 .

[0102] Example 10

[0103] This embodiment provides a method for protecting tenons from aluminum infiltration with air duct holes, comprising the following steps:

[0104] S1: Use paper tape to seal the air inlet hole at the tenon;

[0105] S2: Prepare the first coating according to the raw material ratio in Example 2. After the metal powder is prepared, ball mill it for 1.5 hours, and then ball mill it for 1 hour after solid-liquid mixing. Apply the first coating that has been ball milled to the surface of the tenon to be protected, with a thickness of 1mm to 2mm / layer. After the coating is completed, place the part in an oven at 100°C and bake it for 50 minutes. After the previous layer of coating is completely cured, apply the next layer, and then dry it after coating. Apply 2 layers in total to form a first coating;

[0106] After the first coating is applied and dried, remove the remaining coating that has flowed or accidentally applied to the surface that needs to be aluminized (such as the blade body);

[0107] S3: Prepare the coating according to the proportion of Example 2, ball-mill the solid powder for 1.5 hours after preparation, and ball-mill for another 1.5 hours after solid-liquid mixing, and apply the ball-milled coating on the tenon surface coated with the first coating, with a thickness of 1 mm to 2 mm per layer. After coating, place the workpiece with the tenon facing upward in an oven at 100° C. and bake for 50 minutes until the previous layer of coating is completely cured, and then apply the next layer, and perform drying after coating. A total of 3 layers are applied to form a second coating;

[0108] After the second coating is dried, the residual coating that has flowed or accidentally applied to the surface that needs to be aluminized (such as the blade body) is removed; the protective coating of the transition area between the aluminized surface and the non-aluminized surface is arranged to expose part of the metal matrix in the transition area;

[0109] S4: According to the requirements of aluminizing the parts, the aluminizing surface of the protected parts is sandblasted, and after sandblasting, the parts are placed in a vapor phase aluminizing furnace for aluminizing. The aluminizing temperature is 1080°C and the aluminizing holding time is 6 hours.

[0110] After aluminizing is completed, take out the parts and tap the tenon protective layer with a wooden hammer. The protective coating will peel off and there will be no coating residue.

[0111] The aluminized parts of Example 10 were subjected to overall sand blasting. After sand blasting, the parts were placed in an air box furnace for color treatment at 580°C for 1 hour. After color treatment, the aluminized surface was yellow and the tenon part was blue, indicating that there was no aluminized layer on the tenon and the protection was effective.

[0112] Comparative Example 1

[0113] The only difference between this comparative example and Example 10 is that only the first coating is applied to the surface of the tenon to form an anti-seepage protective layer.

[0114] As a result, due to the low aluminum content in the first coating, it could not fill the solid phase gaps well at high temperature, could not form a dense protective layer, and could not achieve a complete anti-seepage effect, causing aluminum infiltration in the tenon.

[0115] Comparative Example 2

[0116] The only difference between this comparative example and Example 10 is that only the second coating is coated on the surface of the tenon to form an anti-seepage protective layer.

[0117] Results Due to the high aluminum content in the second coating, the excess aluminum at high temperature not only filled the solid phase gaps in the coating, but also had the risk of local point bonding with the base metal. After the aluminum infiltration was completed, the coating was difficult to remove and the alloy composition of the base metal was destroyed.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high temperature aluminized protective coating, characterized in that: The high-temperature aluminizing protective coating is used for aluminizing protection, and comprises a first coating coated on the surface of a substrate and a second coating coated on the surface of the first coating; The first coating layer includes a first coating material, wherein the raw materials of the first coating material include metal powders Ni, Cr, Al and a binder; The second coating layer comprises a second coating material, the raw materials of the second coating material comprise metal powders Ni, Cr, Al and a binder, and the amount of metal powder Al in the first coating material is less than the amount of metal powder Al in the second coating material.

2. The high temperature aluminized protective coating according to claim 1, characterized in that: The usage ratio of the metal powders Ni, Cr and Al in the first coating is 10-15:2-5:0.5-1.

3. The high temperature aluminized protective coating according to claim 1, characterized in that: The usage ratio of the metal powders Ni, Cr and Al in the second coating is 10-14:4-6:2-5.

4. The high temperature aluminized protective coating according to claim 1, characterized in that: The binder is a polyvinyl alcohol aqueous solution with a concentration of 5% to 15%.

5. The high temperature aluminized protective coating according to claim 1, characterized in that: The thickness of the first coating layer is 2-6 mm, and the thickness of the second coating layer is 3-6 mm.

6. The high temperature aluminized protective coating according to claim 1, characterized in that: The method for preparing the first coating and the second coating comprises the following steps: The raw metal powders Ni, Cr and Al in the first coating are added to a ball mill and ground into a mixture, a binder is added to the mixture, and then ball milling is performed to obtain the first coating; The raw metal powders Ni, Cr and Al in the second coating are added to a ball mill and crushed to obtain a mixture. A binder is added to the mixture, and then ball milling is performed to obtain the second coating.

7. A method for protecting tenons from aluminizing with air ducts, characterized in that: The following steps are involved: S1: A protective piece is provided at the air inlet hole of the tenon to seal the air inlet hole; S2: applying a first coating on the surface of the tenon, and curing the first coating to form a first coating; S3: applying a second coating on the surface of the first coating on the tenon, and curing the second coating to form a second coating, so that the high-temperature aluminized protective coating according to any one of claims 1 to 6 is formed on the tenon; S4: The parts with tenons are subjected to sandblasting and aluminizing treatment. After aluminizing, the parts are taken out and the coating on the tenons is knocked to peel off.

8. The method for aluminizing and protecting tenons with air ducting holes according to claim 7, characterized in that: The method also includes applying the first coating several times, and placing the tenon in an oven for baking after each application to solidify the first coating; The second coating is applied several times, and after each application, the tenon is placed in an oven to bake to cure the second coating.

9. The method for protecting tenons by aluminizing with air ducts according to claim 7, characterized in that: The protective member is one of a paper tape or a nickel foil.

10. The method for protecting tenons by aluminizing with air ducts according to claim 7, characterized in that: It also includes finishing the paint on the parts and removing the excess after the first or second coat.

Images