Alumina-yttria core-shell structured / nickel-based composite powder and laser cladding coating

Abstract

The application belongs to the technical field of laser cladding metal-based composite coating, and particularly relates to an alumina-yttria core-shell structure / nickel-based composite powder and a laser cladding coating. The preparation method of the composite powder comprises the following steps: dispersing yttrium nitrate and alpha-Al2O3 in deionized water, adding urea, and then heating and stirring to obtain a mixed powder; the mixed powder is cleaned and dried to obtain a precursor powder; the precursor powder is calcined to obtain an alumina-yttria core-shell structure powder; the alumina-yttria core-shell structure powder and a nickel-based powder are mixed, anhydrous ethanol is added, and wet grinding is performed to obtain a mixed slurry which is dried to obtain the composite powder. The composite powder is prepositioned on the surface of a pretreated substrate to perform laser cladding to obtain a composite laser cladding coating. The hard phase is wrapped with rare earth oxides, so that the characteristics of rare earth elements, such as grain refinement, purification of the structure, reduction of the dilution rate, improvement of the coating structure and mechanical properties, can be fully utilized to improve the forming quality and performance of the cladding layer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of laser cladding metal-based composite coating, and particularly relates to an alumina-yttria core-shell structure / nickel-based composite powder and a laser cladding coating. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission or any kind of suggestion that this information forms the general prior art previously visualized by those working in the field.

[0003] Laser cladding is a method of forming a metallurgical bonded additive cladding layer on the surface of a substrate by adding cladding material on the surface of the substrate and using a high-energy-density laser beam to melt the cladding material together with a thin layer on the surface of the substrate. Preparing a surface strengthening coating by using laser cladding technology is one of the important ways to improve the service performance of materials. Laser cladding technology has many advantages, such as high metallurgical bonding strength, low heat input, greatly reduced thermal deformation, controllable coating thickness, wide range of composite powder selection, etc. Generally, the composition and microstructure of the coating can be adjusted by changing the cladding process according to the working conditions, so as to improve the performance and prolong the service life of the parts. However, there are several defects in the laser cladding process, (1) the coating powder is prone to moisture, oxidation or oxidation reaction at high temperature before cladding, which can produce pores due to the production of gas; (2) under the premise of meeting good metallurgical bonding, it is easy to have too high dilution rate; (3) due to the fast cooling speed, it is easy to cause composition segregation and uneven microstructure of the cladding layer; (4) due to the difference in physical properties such as melting point between the substrate and the cladding layer material, combined with the rapid heating and extremely cold effect of high-density laser, it is easy to produce large residual thermal stress, which induces cracks in the cladding layer and causes damage to the parts. SUMMARY

[0004] In order to reduce the problems such as pores, cracks and high dilution rate of the laser cladding ceramic reinforced metal-based composite coating, and promote the uniform distribution of the reinforcing phase in the cladding layer, the purpose of the present application is to provide an alumina-yttria core-shell structure / nickel-based composite powder and a laser cladding coating. The present application uses homogeneous precipitation method to prepare (Al2O3-Y2O3) core-shell structure, which is added into Ni60 powder as a reinforcing phase to form a composite cladding powder to prepare a laser cladding coating. By wrapping the hard phase with rare earth oxides, the characteristics of rare earth elements such as grain refinement, purification of microstructure, reduction of dilution rate, improvement of coating microstructure and mechanical properties can be fully utilized to improve the forming quality and performance of the cladding layer.

[0005] In order to achieve the above-mentioned purpose, the present application realizes the technical scheme as follows:

[0006] In a first aspect, the present application provides a preparation method of an alumina-yttria core-shell structure / nickel-based composite powder, comprising the following steps:

[0007] dispersing yttrium nitrate and α-Al2O3 in deionized water, adding urea and then heating and stirring to obtain a mixed powder, washing and drying the mixed powder to obtain a precursor powder, and calcining the precursor powder to obtain an alumina-yttria core-shell structure powder;

[0008] mixing the alumina-yttria core-shell structure powder and a nickel-based powder, adding anhydrous ethanol for wet milling and mixing, and drying the obtained mixed slurry to obtain the alumina-yttria core-shell structure / nickel-based composite powder.

[0009] Preferably, the particle size of α-Al2O3 is 40-60 nm, the molar ratio of yttrium nitrate to α-Al2O3 is 3:2-3, and the concentration of yttrium nitrate dispersed in deionized water is 0.014-0.016 mol / L; the concentration of urea is 0.4-0.6 mol / L.

[0010] Preferably, the calcination temperature is 550-650℃, and the time is 1.9-2.1 h.

[0011] Preferably, the nickel-based powder comprises Ni60, the particle size of the nickel-based powder is 45-75 μm, and the mass of the alumina-yttria core-shell structure powder is 1-3 wt% of the sum of the masses of the alumina-yttria core-shell structure powder and the nickel-based powder.

[0012] Preferably, the ball powder ratio for wet milling and mixing is 50:3, the rotation speed is 20 rpm, and the ball milling time is 24 h.

[0013] In a second aspect, the present application provides an alumina-yttria core-shell structure / nickel-based composite powder obtained by the preparation method of the first aspect.

[0014] In a third aspect, the present application provides a laser cladding method of an alumina-yttria core-shell structure / nickel-based composite laser cladding coating, comprising the following steps:

[0015] pretreating the surface of a substrate to remove surface rust and oxide layers;

[0016] prepositioning the alumina-yttria core-shell structure / nickel-based composite powder of the second aspect on the surface of the substrate, and performing laser cladding under a protective atmosphere to obtain an alumina-yttria core-shell structure / nickel-based composite laser cladding coating.

[0017] Preferably, the pretreatment is ordinary polishing treatment or special processing treatment.

[0018] Preferably, the pre-layer is pre-set on the surface of the substrate by mixing the alumina-yttria core-shell structure / nickel-based composite powder as described in the second aspect with alcohol and co-drying; the protective atmosphere comprises argon or nitrogen.

[0019] In a fourth aspect, the present application provides an alumina-yttria core-shell structure / nickel-based composite laser cladding coating, which is characterized in that it is obtained by the laser cladding method as described in the third aspect.

[0020] The one or more technical solutions of the present application have the following beneficial effects:

[0021] The present application uses a homogeneous precipitation method to wrap Y2O3 outside the hard Al2O3 particles to form a complete core-shell structure composite particle, which fully utilizes the characteristics of rare earth elements, and can refine the coating grain and make the structure uniform compared with adding Al2O3 and Y2O3 alone.

[0022] The present application has the characteristics of low cost, simple process and excellent performance, and can realize industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings accompanying the specification of the present application form a part thereof and serve to provide further understanding of the present application, the illustrative embodiments of the present application and its description serve to explain the present application, and do not constitute an improper limitation of the present application.

[0024] Figure 1 is a flow chart of the laser cladding method of the alumina-yttria core-shell structure / nickel-based composite laser cladding coating of the present application;

[0025] Figure 2 is the SEM&EDS diagram of the alumina-yttria core-shell structure powder in Example 1;

[0026] Figure 3 is the XRD diagram of the alumina-yttria core-shell structure powder in Example 1;

[0027] Figure 4 is the TEM&EDS diagram of the alumina-yttria core-shell structure powder in Example 1;

[0028] Figure 5 is the microstructure morphology diagram of the laser cladding formed part in Example 1;

[0029] Figure 6 is the microstructure morphology diagram of the laser cladding formed part in Comparative Example 1;

[0030] Figure 7 is the hardness comparison diagram of the laser cladding formed parts in Example 1 and Comparative Example 1 of the present application;

[0031] Figure 8 is a friction coefficient comparison chart of the laser cladding formed piece in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0032] In order to enable a person skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples and comparative examples.

[0033] Example 1

[0034] As shown in Figure 1 , the laser cladding method of the alumina-yttria core-shell structure / nickel-based composite laser cladding coating comprises the following steps:

[0035] (1) Pre-treat the surface of the substrate H13 steel to be cladded to remove surface rust and oxide layer;

[0036] (2) Prepare the alumina-yttria core-shell structure powder: disperse yttrium nitrate hexahydrate and nano α-Al2O3 in deionized water, maintain the content of Y 3+ in the solution at 0.015 mol / L, and maintain the molar ratio of yttrium nitrate to α-Al2O3 at 3:2.5, use 0.5 mol / L urea as the precipitant, heat and stir in a water bath heater at 90°C for 3h, wash the product with deionized water and anhydrous ethanol three times respectively, dry at 85°C for 12h, and finally calcine at 600°C for 2h.

[0037] (3) Prepare the alumina-yttria core-shell structure / nickel-based composite powder by wet ball milling: mix 2wt.% alumina-yttria core-shell structure powder with 98wt.% Ni60A powder, add a small amount of anhydrous ethanol for wet milling and mixing, and then dry the mixed slurry in a 85°C vacuum drying oven for 12h;

[0038] (4) Laser cladding: pre-position the alumina-yttria core-shell structure / nickel-based composite powder on the surface of the substrate, and perform laser cladding under argon protection to successfully obtain a composite coating with uniform structure. The specific cladding process parameters are as follows: laser power is 1300W, spot size is 2mm, scanning speed is 6mm / s, overlap rate is 40%, and pre-positioned layer thickness is 1.5mm.

[0039] As shown in Figure 2 , the alumina-yttria core-shell structure powder is successfully prepared by homogeneous precipitation method, and Al, Y and O elements are uniformly distributed without doping other impurity elements. As shown in Figure 3 , the alumina-yttria core-shell structure powder is composed of alumina and yttria without other impurities. As shown in Figure 4 , the core-shell boundary of the alumina-yttria core-shell structure powder is obvious.

[0040] Comparative Example 1

[0041] The difference from Example 1 is that the cladding powder in Comparative Example 1 is Ni60A+Y2O3+Al2O3 alloy powder. Y2O3 and Al2O3 are added separately in a molar ratio of 3:5 and do not form a core-shell structure. The other steps are the same as in Example 1.

[0042] like Figure 5 , Figure 6 As shown, compared with Comparative Example 1, the addition of a core-shell structure (Al2O3-Y2O3) in Example 1 resulted in a refinement of the microstructure morphology of the cladding layer to a certain extent.

[0043] like Figure 7 As shown, compared with Comparative Example 1 where Y2O3 and Al2O3 were added alone, the hardness of the cladding layer in Example 1 increased after adding a core-shell structure (Al2O3-Y2O3).

[0044] like Figure 8 As shown, the friction coefficient of the cladding layer decreased after adding the core-shell structure (Al2O3-Y2O3).

[0045] Example 2

[0046] The laser cladding method for alumina-yttrium oxide core-shell structure / nickel-based composite laser cladding coating includes the following steps:

[0047] (1) Pre-treat the surface of the H13 steel substrate to be clad to remove surface rust and oxide layer;

[0048] (2) Preparation of alumina-yttrium oxide core-shell structured powder: Yttrium nitrate hexahydrate and nano-α-Al2O3 were dispersed in deionized water, so that the Y2O3 in the solution... 3+ The content was maintained at 0.015 mol / L, and the molar ratio of yttrium nitrate to α-Al2O3 was kept at 3:2. 0.5 mol / L urea was used as the precipitant. The mixture was heated and stirred at 90°C for 3 h in a water bath with a stirrer. The product was washed three times with deionized water and anhydrous ethanol, dried at 85°C for 12 h, and finally calcined at 600°C for 2 h.

[0049] (3) Preparation of alumina-yttrium core-shell structure / nickel-based composite powder by wet ball milling: 2 wt.% alumina-yttrium core-shell structure powder was mixed with 98 wt.% Ni60A powder, a small amount of anhydrous ethanol was added for wet milling, and then the mixture was dried in a vacuum drying oven at 85℃ for 12 h.

[0050] (4) Laser cladding: the alumina-yttria core-shell structure / nickel-based composite powder is pre-positioned on the surface of the substrate, and a uniform composite coating is successfully obtained by laser cladding under the protection of argon. The specific cladding process parameters are as follows: laser power is 1300W, spot size is 2mm, scanning speed is 6mm / s, overlap rate is 40%, and pre-positioned layer thickness is 1.5mm.

[0051] Example 3

[0052] The laser cladding method of the alumina-yttria core-shell structure / nickel-based composite laser cladding coating comprises the following steps:

[0053] (1) The surface of the substrate H13 steel to be cladded is pretreated to remove surface rust and oxide layer;

[0054] (2) Preparation of alumina-yttria core-shell structure powder: yttrium nitrate hexahydrate and nano α-Al2O3 are dispersed in deionized water, the content of Y 3+ in the solution is maintained at 0.015mol / L, and the molar ratio of yttrium nitrate to α-Al2O3 is maintained at 1:2, 0.5mol / L urea is used as a precipitant, the mixture is heated and stirred in a water bath heater at 90℃ for 3h, the product is washed with deionized water and anhydrous ethanol three times respectively, dried at 85℃ for 12h, and finally calcined at 600℃ for 2h;

[0055] (3) Wet ball milling to prepare alumina-yttria core-shell structure / nickel-based composite powder: 2wt.% alumina-yttria core-shell structure powder and 98wt.% Ni60A powder are mixed, a small amount of anhydrous ethanol is added for wet milling, and then the mixed slurry is dried in a vacuum drying oven at 85℃ for 12h;

[0056] (4) Laser cladding: the alumina-yttria core-shell structure / nickel-based composite powder is pre-positioned on the surface of the substrate, and a uniform composite coating is successfully obtained by laser cladding under the protection of argon. The specific cladding process parameters are as follows: laser power is 1300W, spot size is 2mm, scanning speed is 6mm / s, overlap rate is 40%, and pre-positioned layer thickness is 1.5mm.

[0057] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. Use of an alumina-yttria core-shell structure / nickel-based composite powder in the preparation of an alumina-yttria core-shell structure / nickel-based composite laser cladding coating; The preparation method of the alumina-yttria core-shell structure / nickel-based composite powder comprises the following steps: yttrium nitrate and α-Al2O3 are dispersed in deionized water, and a mixed powder is obtained after adding urea and heating and stirring; the mixed powder is washed and dried to obtain a precursor powder, and the precursor powder is calcined to obtain an alumina-yttria core-shell structure powder; The alumina-yttria core-shell structure powder is mixed with a nickel-based powder, and then anhydrous ethanol is added for wet milling and mixing; the obtained mixed slurry is dried to obtain the alumina-yttria core-shell structure / nickel-based composite powder; The molar ratio of yttrium nitrate to α-Al2O3 is 3:2-3, and the concentration of yttrium nitrate dispersed in deionized water is 0.014-0.016 mol / L; The mass of the alumina-yttria core-shell structure powder is 1-3 wt% of the sum of the mass of the alumina-yttria core-shell structure powder and the nickel-based powder.

2. Use according to claim 1, wherein The particle size of α-Al2O3 is 40-60 nm; and the concentration of urea is 0.4-0.6 mol / L.

3. The use according to claim 1, wherein The calcination temperature is 550-650 ℃, and the time is 1.9-2.1 h.

4. The use according to claim 1, wherein The nickel-based powder comprises Ni60, and the particle size of the nickel-based powder is 45-75 μm.

5. The use according to claim 1, wherein The ball powder ratio of wet milling and mixing is 50:3, the rotation speed is 20 rpm, and the ball milling time is 24 h.

6. An alumina-yttria core-shell structure / nickel-based composite powder, characterized by, The preparation method of the alumina-yttria core-shell structure / nickel-based composite powder comprises the following steps: yttrium nitrate and α-Al2O3 are dispersed in deionized water, and a mixed powder is obtained after adding urea and heating and stirring; the mixed powder is washed and dried to obtain a precursor powder, and the precursor powder is calcined to obtain an alumina-yttria core-shell structure powder; The alumina-yttria core-shell structure powder is mixed with a nickel-based powder, and then anhydrous ethanol is added for wet milling and mixing; the obtained mixed slurry is dried to obtain the alumina-yttria core-shell structure / nickel-based composite powder; The molar ratio of yttrium nitrate to α-Al2O3 is 3:2-3, and the concentration of yttrium nitrate dispersed in deionized water is 0.014-0.016 mol / L; The mass of the alumina-yttria core-shell structure powder is 1-3 wt% of the sum of the mass of the alumina-yttria core-shell structure powder and the nickel-based powder.

7. A laser cladding method of an alumina-yttria core-shell structure / nickel-based composite laser cladding coating, characterized by, comprises the following steps: The surface of the substrate is pretreated to remove surface rust and oxide layer; The alumina-yttria core-shell structure / nickel-based composite powder of claim 6 is prepositioned on the surface of the substrate, and laser cladding is performed under a protective atmosphere to obtain an alumina-yttria core-shell structure / nickel-based composite laser cladding coating.

8. The laser cladding method of claim 7, wherein, The pretreatment is ordinary polishing treatment or special processing treatment.

9. The laser cladding method of claim 7, wherein, The alumina-yttria core-shell structure / nickel-based composite powder of claim 6 is mixed with alcohol and co-dried to form a prepositioned layer on the surface of the substrate; and the protective atmosphere comprises argon or nitrogen.

10. An alumina-yttria core-shell structure / nickel-based composite laser cladding coating, characterized in that, Obtained by the laser cladding method of any one of claims 7-9.

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