Aging heat treatment method for high hardness nickel-based alloy laser cladding coating

Abstract

The application discloses an aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating and belongs to the technical field of coating preparation. First, a nickel-based alloy powder is prepared, which comprises 50-60% of Ni45, 0-10% of Nb, 20-30% of NbC, 0-10% of WC and 0-5% of Y2O3 in terms of mass fraction; then, the nickel-based alloy powder is subjected to ball-milling alloying modification treatment by using a ball-milling method; meanwhile, the relationship between hardness and plasticity is solved by adopting an aging heat treatment method, so that a copper alloy with the high-hardness nickel-based alloy cladding coating is prepared. The coating hardness is further improved through two steps, and finally, the problems of easy deformation of the copper plate caused by heating, high hardness of the coating, great brittleness of the coating and serious cracking of the coating in the direct preparation process (namely one-step preparation) can be avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coating preparation, and particularly relates to an aging heat treatment method of a high-hardness nickel-based alloy laser cladding coating. BACKGROUND

[0002] Copper and copper alloys are widely used in various fields such as electronics, petrochemical industry and mechanical industry due to their excellent electrical conductivity, thermal conductivity and plasticity. However, due to the harsh working environment, general copper alloys cannot meet the production requirements. In order to improve the performance of copper alloys, an alloy coating is usually cladded on the surface of the copper alloys.

[0003] Compared with other base alloy materials, when a high-performance nickel-based alloy coating is prepared on the copper alloy, the coating is prone to cracking in the cladding process due to the characteristics of the copper alloy, such as high thermal conductivity, good plasticity and large thermal deformation, and it is difficult to prepare a high-hardness coating on the surface of the copper alloy. In addition, the nickel-based alloy powder used has the characteristics of large composition difference, high hardness and different melting points, which makes the prepared coating have very high hardness and further increases the possibility of cracking. In the traditional preparation of a nickel-based alloy coating on the surface of a copper alloy, the nickel-based alloy powder is mechanically mixed, and then a layer of nickel-based alloy coating is cladded on the surface of the base body by using laser as a heat source. However, since high hardness and plasticity are a pair of contradictory relationship, the high hardness produced by this method will inevitably cause brittleness, resulting in cracking of the coating, and the hardness is difficult to be further improved. Therefore, it is urgent to develop a method to make the nickel-based alloy coating on the surface of the copper base have high hardness and no cracking performance, so as to meet the actual production requirements. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide an aging heat treatment method of a high-hardness nickel-based alloy laser cladding coating, which effectively solves the problem of cracking when further preparing a high-hardness nickel-based alloy coating on the surface of a copper base.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application discloses an aging heat treatment method of a high-hardness nickel-based alloy laser cladding coating, and the steps are as follows:

[0007] 1) Cladding the nickel-based alloy powder after ball milling treatment on the surface of the copper alloy;

[0008] 2) Aging heat treatment of the copper alloy with cladded nickel-based alloy powder to obtain a copper alloy with cladded high-hardness nickel-based alloy coating.

[0009] Preferably, a pure nickel transition layer is cladded on the surface of the copper alloy before step 1).

[0010] Further preferably, the copper alloy surface is polished and cleaned with alcohol before a pure nickel transition layer is cladded on the copper alloy surface.

[0011] Preferably, in step 1), ball milling is performed by using a ball mill.

[0012] Preferably, in step 1), the nickel-based alloy powder comprises 50-60% of Ni45, 0-10% of Nb, 20-30% of NbC, 0-10% of WC and 0-5% of Y2O3 by mass fraction.

[0013] Preferably, in step 1), the ball milling is performed at a positive and negative rotation speed of 5-10 rad / s for 15-20 min, with a rest time of 5-15 min, and a total ball milling time of 120-180 min.

[0014] Preferably, in step 1), the cladding is laser cladding.

[0015] Further preferably, the laser cladding is performed at a power of 2.7-3.6 KW, a scanning speed of 30-45 mm / s, and a step distance of 1.5-2.0 mm.

[0016] Preferably, the laser cladding is performed at a powder feeding speed of 30-50 r / min.

[0017] Preferably, in step 2), the aging heat treatment is performed at a temperature of 350-550 ℃ for 30-50 h, and is air-cooled.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The application provides an aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating.

[0020] Further, in the high-speed laser cladding process, the nickel-based alloy powder after ball milling alloying can be uniformly heated and melted by laser before impacting the surface of the substrate, and a high-plasticity nickel-based alloy coating is formed on the surface of the copper substrate. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a nickel-based alloy powder ball milling morphology;

[0022] Figure 2 It is a nickel-based alloy ball milling powder Eds analysis result graph; wherein a is Ni, b is Nb, and c is Y;

[0023] Figure 3 It is a nickel-based alloy powder mechanical mixing morphology;

[0024] Figure 4 It is a coating macro-morphology dyeing flaw detection graph after powder ball milling treatment and cladding;

[0025] Figure 5 It is a micro-morphology graph of the nickel-based alloy powder after ball milling and cladded on the surface of the copper alloy; wherein a is the overall cladding, b is the area of surface scanning, c1 is the distribution of the Ni element, c2 is the distribution of the Nb element, c3 is the distribution of the Y element, c4 is the distribution of the Fe element, c5 is the distribution of the C element, and c6 is the distribution of the Cr element;

[0026] Figure 6It is the coating corrosion microstructure morphology chart after ball milling and before heat treatment; wherein, a is the top, b is the middle, and c is the bottom;

[0027] Figure 7 It is the coating hardness change chart before and after 500 DEG C heat treatment based on high hardness nickel-based alloy laser cladding coating;

[0028] Figure 8 It is the coating corrosion microstructure chart after 500 DEG C heat treatment based on high hardness nickel-based alloy laser cladding coating; wherein, a is the top, b is the middle, and c is the bottom;

[0029] Figure 9 It is the coating hardness change chart before and after 800 DEG C heat treatment based on high hardness nickel-based alloy laser cladding coating;

[0030] Figure 10 It is the coating corrosion microstructure chart after 800 DEG C heat treatment based on high hardness nickel-based alloy laser cladding coating; wherein, a is the top, b is the middle, and c is the bottom. DETAILED DESCRIPTION

[0031] In order to make the personnel in the technical field better understand the application scheme, the technical scheme in the embodiment of the application will be described clearly and completely in the embodiment of the application combined with the drawings in the embodiment of the application. Obviously, the described embodiment is only a part of the embodiment of the application, not all. Based on the embodiment in the application, all other embodiments obtained by the ordinary skilled in the art without creative labor should belong to the protection scope of the application.

[0032] It should be noted that the terms "first", "second" and the like in the specification and claims of the application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0033] The application will be described in further detail below in conjunction with the drawings:

[0034] The application provides an aging heat treatment method based on high hardness nickel-based alloy laser cladding coating, and the steps are as follows:

[0035] 1. Pretreatment

[0036] The surface of the copper alloy to be treated is polished and cleaned with alcohol.

[0037] 2. Preparing the transition layer

[0038] The surface of the copper alloy after polishing and cleaning is laser cladded with a layer of pure nickel transition layer using pure nickel powder as the transition layer powder. The laser cladding equipment used is a six-axis robot, a 6KW fiber laser, a powder feeder, a gas feeding system and an integrated system control cabinet. The cladding parameters are: laser power of 2.7-3.6KW, scanning speed of 30-45mm / s, step distance of 1.5-2.0mm, and powder feeding speed of 30-50r / min.

[0039] 3. Preparing the cladding layer

[0040] 1) Preparing the nickel-based alloy powder

[0041] The nickel-based alloy powder comprises 50-60% of Ni45, 0-10% of Nb, 20-30% of NbC, 0-10% of WC and 0-5% of Y2O3 by mass fraction. The nickel-based alloy powder is prepared according to the above-mentioned proportions as the cladding powder.

[0042] 2) Ball milling

[0043] The nickel-based alloy powder prepared in step 1) is placed in a ball mill for ball milling treatment. The forward and reverse rotation speed of the ball mill is 5-10rad / s, the forward and reverse rotation time is 15-20min, the rest time is 5-15min, and the total ball milling time is 120-180min.

[0044] 3) Cladding

[0045] A layer of ball-milled nickel-based alloy coating is laser cladded on the surface of the copper alloy with the transition layer cladded in step 2. The laser cladding equipment used is a six-axis robot, a 6KW fiber laser, a powder feeder, a gas feeding system and an integrated system control cabinet. The cladding parameters are: laser power of 2.7-3.6KW, scanning speed of 30-45mm / s, step distance of 1.5-2.0mm, and powder feeding speed of 30-50r / min. The copper alloy with the surface cladded with the nickel-based alloy coating is obtained. Then, whether the coating has cracks is detected by coloring flaw detection, and the composition and morphology of the coating are observed.

[0046] 4. Aging heat treatment

[0047] The copper alloy with the surface cladded with the nickel-based alloy coating obtained in step 3 is placed in a heat treatment furnace for relevant heat treatment, and the heat treatment parameters are as follows: the temperature is 350-550 DEG C, the time is 30-50 h, and the cooling mode is air cooling. After the heat treatment is completed, the copper alloy is taken out, and a micro Vickers hardness tester is used for hardness testing, and the micro hardness testing parameters are as follows: the test load is 100 gf, the holding time is 10 s, the test interval is 100 mu m, and the microstructure morphology change of the copper alloy after the heat treatment is observed.

[0048] Example 1

[0049] 1. Pretreatment

[0050] The surface of the Cu-Cr-Zr alloy is polished and cleaned with alcohol.

[0051] 2. Preparation of transition layer

[0052] Pure nickel powder is used as the transition layer powder, and a layer of pure nickel transition layer is laser cladded on the surface of the Cu-Cr-Zr alloy after polishing and cleaning. The laser cladding equipment used is a six-axis robot, a 6KW fiber laser, a powder feeder, a gas feeding system and an integrated system control cabinet, and the cladding parameters are as follows: the laser power is 3.0 KW, the scanning speed is 35 mm / s, the step distance is 1.8 mm, and the powder feeding speed is 40 r / min.

[0053] 3. Preparation of cladding layer

[0054] 1) Preparation of nickel-based alloy powder

[0055] The nickel-based alloy powder includes 50% of Ni45, 10% of Nb, 30% of NbC, 5% of WC and 5% of Y2O3 in terms of mass fraction, and the nickel-based alloy powder is prepared according to the above-mentioned proportion as the cladding powder;

[0056] 2) Ball milling

[0057] The prepared nickel-based alloy powder is placed in a ball mill with set parameters for ball milling treatment, and the forward and reverse rotation speed of the ball mill is 5 rad / s, the forward and reverse rotation time of the ball mill is 15 min, the rest time is 5 min, and the total ball milling time is 120 min;

[0058] 3) Cladding

[0059] A ball-milled nickel-based alloy coating was laser-laminated onto a 3cm thick Cu-Cr-Zr alloy surface with a transition layer. The laser cladding equipment used included a six-axis robot, a 6kW fiber laser, a powder feeder, a gas supply system, and an integrated system control cabinet. The cladding parameters were: laser power 3.0kW, scanning speed 35mm / s, step size 1.8mm, and powder feed speed 40r / min. This resulted in a copper alloy with a nickel-based alloy coating. The coating was then inspected for cracks and its composition and microstructure were observed.

[0060] See ball-milled morphology composition. Figure 1 and Figure 2 The morphology of conventionally mechanically mixed nickel-based alloy powders is shown in [reference]. Figure 3 . Figure 3 Powders mixed mechanically are simply several powders mixed together. However... Figure 1 and Figure 2 The powder after ball milling was not broken down by the high-speed grinding balls and remained spherical. The main body of the powder consisted of large Ni45 particles. Compared to the original powder, the surface of the dry-milled powder became rougher and was coated with a layer of fine flocculent material. Figure 2 Energy dispersive spectroscopy (EDS) analysis revealed that the surface scan results for Ni elements were lighter in color and had fewer particles, while the surface scan results for Nb and Y elements were darker in color and the particle distribution areas overlapped with those for Ni elements. This indicates that the powder morphology after dry milling is mainly Ni45 powder, with Nb, NbC, and Y2O3 powder particles uniformly embedded on the softer Ni45 powder surface, ultimately forming a powder coating state. Therefore, this experiment used the ball-milled powder as the cladding powder.

[0061] The ball-milled powder was fused onto the substrate surface, and the results of dye penetrant testing were performed on the macroscopic morphology of the coating surface. Figure 4 It can be seen that the coating as a whole has virtually no cracks. However, coatings prepared by traditional methods show obvious cracking, mainly because a high-hardness nickel-based alloy coating is directly prepared on the substrate surface. The excessive hardness leads to low plasticity. In addition, the thermal stress concentration during the laser cladding process and the easy deformation of the substrate due to heat make the coating very prone to cracking.

[0062] See the overall microstructure of the coating. Figure 5 For the microstructure of the coating after ball milling and before heat treatment, please refer to [reference needed]. Figure 6 ,from Figure 5 In section a, it can be observed that the entire coating consists of a cladding layer, a transition layer, and a substrate, without any related cracks. (Bond surface scan) Figure 5 b and Figure 5 From c1 to c6, it can be observed that these irregular structures are mainly composed of Ni, Nb, Fe, and Cr elements. Figure 5The white particles in the Ni matrix are mainly composed of Nb elements and are dispersed and relatively uniformly distributed throughout the coating. No black carbide structures were observed in the microstructure, indicating that they did not precipitate to form hard and brittle carbides, but rather remained dissolved in the Ni matrix.

[0063] 4. Aging heat treatment

[0064] After completing the cladding process in step 3 according to specifications, the copper alloy with a nickel-based alloy coating was wire-cut into heat-treated samples approximately 10mm x 10mm in length and width. These samples were then placed in a heat treatment furnace for heat treatment. The heat treatment parameters were: temperature 550℃, time 40h, and air cooling. After heat treatment, the samples were removed and their hardness was tested using a micro Vickers hardness tester. The microhardness test parameters were: test load 100gf, holding time 10s, and test interval 100μm. Changes in the microstructure were observed.

[0065] The nickel-based alloy coatings prepared using this method are compared by examining the changes in hardness before and after heat treatment. (See [reference needed]). Figure 7 It can be observed that the coating hardness has increased significantly, by approximately 18% (the highest hardness of the coating is 427 HV). 100 This indicates that the coating underwent age-strengthening during the heat treatment process. Comparing the coating before heat treatment (…), Figure 6 ), observe the microstructure of the coating after corrosion following heat treatment at 500℃. Figure 8 As can be seen, the Ni-based framework exhibits significant shrinkage and gaps, resulting in discontinuities and the formation of some black material. This is mainly due to the precipitation of carbides dissolved in the Ni matrix during heat treatment, causing distortion of the Ni lattice and significantly increasing the coating's hardness. Simultaneously, the increased hardness of the transition layer is primarily due to the diffusion of coating components into the pure Ni layer during heat treatment. Furthermore, the increased internal energy of the Cu matrix under prolonged heat treatment reduces the interaction forces between copper atoms, decreasing the stability of the molecular arrangement and thus softening the matrix. Ultimately, this reduces the hardness difference between the transition layer and the matrix. This demonstrates that this method can improve coating hardness while preventing cracking.

[0066] Example 2

[0067] 1. Preprocessing

[0068] Polish and clean the surface of the Cu-Cr-Zr alloy with alcohol.

[0069] 2. Preparation of transition layer

[0070] The pure nickel powder is used as the transition layer powder, and a pure nickel transition layer is laser cladded on the Cu-Cr-Zr alloy surface after polishing and cleaning. The laser cladding equipment used is a six-axis robot, a 6KW fiber laser, a powder feeder, a gas feeding system and an integrated system control cabinet. The cladding parameters are as follows: the laser power is 3.6KW, the scanning speed is 30mm / s, the step distance is 2.0mm, and the powder feeding speed is 50r / min.

[0071] 3. Preparing the cladding layer

[0072] 1) Preparing the nickel-based alloy powder

[0073] The nickel-based alloy powder comprises 60% of Ni45, 5% of Nb, 25% of NbC, 5% of WC and 5% of Y2O3 by mass fraction. The nickel-based alloy powder is prepared according to the above-mentioned proportion as the cladding powder.

[0074] 2) Ball milling

[0075] The prepared nickel-based alloy powder is placed in the ball mill with the set parameters for ball milling treatment. The forward and reverse rotation speed of the ball mill is 10rad / s, the forward and reverse rotation time of the ball mill is 20min, the rest time is 15min, and the total ball milling time is 160min.

[0076] 3) Cladding

[0077] A layer of ball-milled nickel-based alloy coating is laser cladded on the surface of the Cu-Cr-Zr alloy with a transition layer of 3cm thick. The laser cladding equipment used is a six-axis robot, a 6KW fiber laser, a powder feeder, a gas feeding system and an integrated system control cabinet. The cladding parameters are as follows: the laser power is 3.6KW, the scanning speed is 30mm / s, the step distance is 2.0mm, and the powder feeding speed is 50r / min. Thus, the copper alloy with the nickel-based alloy coating on the surface is obtained.

[0078] 4. Aging heat treatment

[0079] The copper alloy with the nickel-based alloy coating on the surface obtained after the cladding of step 3 is completed according to the specification is wire cut into heat treatment samples with a length and width of about 10mm and 10mm respectively, and then placed in a heat treatment furnace for heat treatment. The heat treatment parameters are as follows: the temperature is 800℃, the time is 8h, and the cooling mode is air cooling. After the heat treatment is completed, the sample is taken out, the hardness is tested by using a micro Vickers hardness tester, the micro hardness testing parameters are as follows: the test load is 100gf, the holding time is 10s, the test interval is 100μm, and the microstructure morphology is observed.

[0080] The hardness test results are shown in Figure 9 By comparing the hardness change of the coating before and after the heat treatment, the hardness of the coating also increases obviously, which increases by about 15%. The maximum hardness of the coating is 419HV100 )。To Figure 10 After heat treatment at 800℃, the microstructure of the coating after corrosion was observed, and the same phenomenon as heat treatment at 500℃ was found, the Ni-based skeleton was obviously contracted and notched, and discontinuity was generated, indicating that the precipitation of carbide in the Ni-based skeleton improved the hardness of the coating.

[0081] From the results of the above examples, it can be found that after aging heat treatment, the hardness of the coating at 500℃ or 800℃ is obviously greatly improved compared with the original coating, which can avoid the cracking problem caused by the high hardness of the coating in the direct preparation process (i.e. one-step preparation), and also provides relevant ideas for further improving the hardness of the coating in the future.

[0082] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. An aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating, characterized in that, The steps are as follows: 1) The nickel-based alloy powder after ball milling is clad onto the surface of the copper alloy; wherein, the nickel-based alloy powder, by mass fraction, includes 50%~60% Ni45, 5%~10% Nb, 20%~30% NbC, 5% WC and 5% Y2O3. 2) The copper alloy coated with nickel-based alloy powder is subjected to aging heat treatment. The cooling method of aging heat treatment is air cooling, the temperature is 350~550℃, and the time is 30~50 h, to obtain a copper alloy coated with a high-hardness nickel-based alloy coating.

2. The aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating according to claim 1, characterized in that, Before step 1), a pure nickel transition layer is fused onto the surface of the copper alloy.

3. The aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating according to claim 2, characterized in that, Before cladding the copper alloy surface with a pure nickel transition layer, the copper alloy surface is polished and cleaned with alcohol.

4. The aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating according to claim 1, characterized in that, In step 1), a ball mill is used for ball milling treatment.

5. The aging heat treatment method for a high-hardness nickel-based alloy laser cladding coating according to claim 1, characterized in that, In step 1), the ball milling process is as follows: the ball milling speed is 5~10 rad / s, the ball milling time is 15~20 min, the rest time is 5~15 min, and the total ball milling time is 120~180 min.

6. The aging heat treatment method based on a high-hardness nickel-based alloy laser cladding coating according to claim 1, characterized in that, In step 1), the cladding is laser cladding.

7. The aging heat treatment method for a high-hardness nickel-based alloy laser cladding coating according to claim 6, characterized in that, The laser cladding power is 2.7~3.6 KW, the laser cladding scanning speed is 30~45 mm / s, and the laser cladding step size is 1.5~2.0 mm.

8. The aging heat treatment method for a high-hardness nickel-based alloy laser cladding coating according to claim 6, characterized in that, The powder feeding speed for laser cladding is 30~50 r / min.

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