Preparation method for in-situ generation of Ti3SiC2 reinforced Co-based coating

Abstract

The invention belongs to the technical field of modified coatings, and particularly relates to a preparation method for in-situ generation of a Ti3SiC2 reinforced Co-based coating, which comprises the following steps: S1, preparing mixed powder: the mixed powder comprises Co powder, Ti powder, Si powder and TiC powder; s2, the mixed powder prepared in the step S1 is subjected to ball milling, and preset composite powder is obtained; and S3, the preset composite powder obtained in the step S2 is subjected to cladding on the surface of a base body through a laser cladding technology, and the in-situ generated Ti3SiC2 reinforced Co-based coating is obtained. According to the method, Ti3SiC2 is generated in situ through laser cladding, so that the phenomena that the wettability and the matching property of a coating matrix are relatively poor, the distribution uniformity is relatively difficult to control and an agglomeration phenomenon is possibly caused due to direct addition of an MAX phase are avoided, the excellent performance of the coating is further ensured, the hardness, the wear resistance and other surface properties of the 45 steel can be effectively improved, and the application range of the 45 steel can be expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of modified coatings, and in particular relates to a preparation method for an in-situ generated Ti3SiC2 reinforced Co-based coating. Background Art

[0002] Today, amidst the booming machinery manufacturing industry, higher performance requirements are being placed on structural steel. In addition to its inherently excellent strength and toughness, its surface properties, such as hardness and wear resistance, are attracting increasing attention. 45 steel, due to its excellent tensile strength and yield strength, is widely used in various industrial fields, including machinery, automotive, and construction. However, its low surface hardness and poor wear resistance are key factors limiting its application. Therefore, improving the hardness and wear resistance of 45 steel is an urgent issue.

[0003] Common surface modification techniques include physical vapor deposition, chemical vapor deposition, surfacing, laser cladding, and thermal spraying. Laser cladding technology has the advantages of being able to produce complex structural components, reducing material loss, using a wide range of materials, and being able to combine different material systems according to working conditions. The coating obtained through laser cladding has a low dilution rate, minimal substrate deformation, a high surface finish, and a strong metallurgical bond between the coating and the substrate, making it less susceptible to flaking. In addition, the high laser energy density and rapid cooling rate can produce a more refined grain structure. By adjusting the laser cladding process, an excellent coating with high hardness and good wear resistance can be obtained, thereby improving the surface properties of 45 steel.

[0004] Cobalt-based alloys have become the focus of attention of researchers at home and abroad due to their excellent high-temperature wear resistance, corrosion resistance, and oxidation resistance. As a self-fluxing alloy powder, during the laser cladding process, the Cr element in the alloy reacts with the C element to form hard carbides. These carbides effectively improve the hardness of the alloy by dispersing in the cobalt alloy matrix. A large number of studies have shown that laser cladding cobalt-based alloy coatings can significantly enhance the wear resistance of the matrix. Among all MAX phases, Ti3SiC2 is a typical representative of ternary layered compounds. Due to its unique layered structure, it has excellent properties similar to metals and ceramics. Therefore, Ti3SiC2, as one of the most widely used ternary compounds in the MAX phase, is currently mainly used in lubricating materials, electrical contact materials and other fields. Based on this, adding Ti3SiC2 to Co-based alloys can enhance the hardness of the material and reduce the wear rate. However, studies have shown that directly adding MAX phase has poor wettability and matching with the coating substrate, and its distribution uniformity is difficult to control, which may cause agglomeration. The in-situ generation of MAX phase coatings by laser cladding can overcome the above defects by forming small and stable particle reinforcement phases through chemical reactions.

[0005] In order to improve the surface properties of 45 steel and expand its application range, it is urgent to invent a composite coating containing a MAX phase metal matrix that is synthesized in situ by laser cladding to improve the hardness and wear resistance of 45 steel. Summary of the Invention

[0006] In view of the deficiencies in the above-mentioned prior art, the present invention provides a method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating, which has high hardness and good wear resistance and can well improve the mechanical properties of the substrate surface.

[0007] The specific technical solutions are as follows:

[0008] A method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating comprises the following steps:

[0009] S1 prepares mixed powder: the mixed powder includes Co powder, Ti powder, Si powder and TiC powder;

[0010] S2 ball-mills the mixed powder prepared in step S1 to obtain a preset composite powder;

[0011] In step S3, the pre-set composite powder obtained in step S2 is clad on the surface of the substrate using a laser cladding process to obtain an in-situ generated Ti3SiC2 reinforced Co-based coating.

[0012] The present invention uses a Ti-Si-TiC powder system to form Ti3SiC2 by laser cladding, which has the following advantages over the Ti-Si-C powder system:

[0013] (1) Compared with C, the carbon element in TiC is "locked" and is more stable under high laser temperature. To a certain extent, it can reduce carbon loss, ensure the stability of the stoichiometric ratio, and improve the reaction reliability. The reaction path of Ti3SiC2 is: Ti+Si→Ti5Si3, Ti+C→TiC, Ti5Si3+TiC→Ti3SiC2. Replacing C with TiC can shorten the reaction chain, avoid the additional synthesis step of the intermediate phase (TiC), and make the reaction faster and more direct.

[0014] (2) TiC particles are wetted by molten Ti and Si, and have high interfacial reaction activity, while C has poor wettability with molten metal (large contact angle) and is easy to agglomerate and float. Therefore, replacing C with TiC can improve the uniformity of the molten pool, promote carbon diffusion, and reduce the residual unreacted carbon. At the same time, the residual unreacted TiC is compatible with the target (high hardness but not a harmful impurity), while the residual free carbon C will reduce the density, conductivity and strength. Therefore, replacing C with TiC can avoid free carbon contamination. The residual TiC can also enhance the hardness and wear resistance of the coating.

[0015] (3) In terms of process parameter tolerance, the Ti-Si-C powder system requires strict control of parameters (e.g., graphite residue is likely to remain at low temperatures, and high temperatures will aggravate burnout), while the Ti-Si-TiC powder system is less sensitive to fluctuations in laser power and scanning speed. Therefore, replacing C with TiC can improve process stability, reduce operational difficulty, and is more suitable for industrial applications.

[0016] (4) As for the uniformity of the structure, TiC as a nucleation point promotes the uniform precipitation of Ti3SiC2, which can refine the grains, while the uneven distribution of C can easily lead to local carbon richness or carbon deficiency, coarse or uneven structure. Therefore, using TiC instead of C can make the coating composition gradient smaller, the microstructure more uniform, and the mechanical properties more consistent.

[0017] Preferably, in step S1, the mass percentage of Co powder is 70% to 90%, the mass percentage of Ti powder is 2.45% to 7.35%, the mass percentage of Si powder is 1.43% to 4.29%, and the mass percentage of TiC powder is 6.12% to 18.36%.

[0018] Furthermore, in step S1, the mass ratio of Co powder to the total amount of Ti powder, Si powder and TiC powder, i.e. Co / (Ti+Si+TiC), is (7-9):(1-3), and the molar ratio of the Ti powder, Si powder and TiC powder is 1:1:2.

[0019] Preferably, in step S1 , the purity of the Co powder, Ti powder, Si powder and TiC powder is 99.0% to 99.9%, and the particle size is 100 to 200 μm.

[0020] Furthermore, in step S2, the ball milling time is 3 to 5 hours, and the rotation speed is 150 to 240 r / min.

[0021] Preferably, in step S3, the substrate is 45 steel. The present invention has no special requirements on the specific size, material, and specifications of the substrate. The substrates well known in the art are applicable to the method of the present invention.

[0022] Preferably, in step S3, the laser cladding process is specifically as follows: laser power is 0.9-1.6 kW; scanning speed is 240-300 mm / min; powder feeding amount is 20-28 g / min; overlap rate is 35%-45%, more preferably 35%-40%.

[0023] Preferably, in step S3, before performing the laser cladding operation, the substrate surface is also pretreated; the pretreatment includes grinding, cleaning and sandblasting; the grinding is preferably sandpaper grinding; the cleaning is preferably alcohol cleaning, and the present invention can remove oil stains on the substrate surface through the cleaning; the particle size of the sand used for the sandblasting is preferably 1 to 2 mm.

[0024] The beneficial effects of the present invention are as follows:

[0025] During the laser cladding process, the pre-placed composite powder and the substrate form a molten pool at high temperature. Ti, Si, and TiC tend to form the self-lubricating phase Ti3SiC2 in situ. This in-situ autogenous generation refines the matrix structure and significantly improves the substrate's microhardness. This in-situ generation of Ti3SiC2 through laser cladding avoids the direct addition of the MAX phase, which suffers from poor wettability and compatibility with the coating substrate, as well as the difficulty in controlling its distribution uniformity and potential agglomeration. This ensures the coating's superior performance, effectively improving the hardness and wear resistance of 45 steel and expanding its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the laser cladding process of the present invention;

[0027] Figure 2 is the average hardness graph of the coating in Examples 1 to 3;

[0028] Figure 3 Graph showing the coefficient of friction of the coatings in Examples 1 to 3;

[0029] Figure 4 These are the wear morphologies of the coatings in Examples 1 to 3. DETAILED DESCRIPTION

[0030] The principles and features of the present invention are described below with reference to examples. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0031] Example 1

[0032] A method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating comprises the following steps:

[0033] S1: Weigh the raw material components according to the mass percentage of Co powder 90%, Ti powder 2.45%, Si powder 1.43%, and TiC powder 6.12% to prepare a mixed powder; wherein the purity of Co powder, Ti powder, Si powder, and TiC powder is 99.9%, and the particle size is 150μm;

[0034] S2: placing the mixed powder prepared in step S1 into a ball mill and milling at a speed of 200 r / min for 3 h to obtain a preset composite powder;

[0035] S3 pre-treats the surface of the 45 steel substrate by sandpaper polishing, alcohol cleaning, and 1mm sandblasting;

[0036] like Figure 1 As shown in the figure, the preset composite powder is clad on the substrate surface by laser cladding technology and synchronous powder feeding method with process parameters of laser power of 1 kW, scanning speed of 300 mm / min, powder feeding amount of 22 g / min, and argon flow rate of 15 L / min to obtain a Ti3AlC2-Co based high temperature wear-resistant coating; the overlap rate is 35% and the thickness is 2 mm.

[0037] Example 2

[0038] A method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating comprises the following steps:

[0039] S1: Weigh the raw material components according to the mass percentage of Co powder 80%, Ti powder 4.9%, Si powder 2.86%, and TiC powder 12.24% to prepare a mixed powder; wherein the purity of Co powder, Ti powder, Si powder, and TiC powder is 99.9%, and the particle size is 150μm;

[0040] S2: The mixed powder prepared in step S1 is placed in a ball mill and milled at a speed of 200 r / min for 3 hours to obtain a pre-set composite powder.

[0041] S3 pre-treats the surface of the 45 steel substrate by sandpaper polishing, alcohol cleaning, and 1mm sandblasting;

[0042] Laser cladding technology and synchronous powder feeding method are used to clad the preset composite powder on the substrate surface with process parameters of laser power of 1kW, scanning speed of 300mm / min, powder feeding amount of 22g / min, and argon flow rate of 15L / min to obtain a Ti3AlC2-Co based high temperature wear-resistant coating; the overlap rate is 35% and the thickness is 2mm.

[0043] Example 3

[0044] A method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating comprises the following steps:

[0045] S1: Weigh the raw material components according to the mass percentage of Co powder 70%, Ti powder 7.35%, Si powder 4.29%, and TiC powder 18.36% to prepare a mixed powder; wherein the purity of Co powder, Ti powder, Si powder, and TiC powder is 99.9%, and the particle size is 150μm;

[0046] S2: placing the mixed powder prepared in step S1 into a ball mill and milling at a speed of 200 r / min for 3 h to obtain a preset composite powder;

[0047] S3 pre-treats the surface of the 45 steel substrate by sandpaper polishing, alcohol cleaning, and 1mm sandblasting;

[0048] Laser cladding technology and synchronous powder feeding method are used to clad the preset composite powder on the substrate surface with process parameters of laser power of 1kW, scanning speed of 300mm / min, powder feeding amount of 22g / min, and argon flow rate of 15L / min to obtain a Ti3AlC2-Co based high temperature wear-resistant coating; the overlap rate is 35% and the thickness is 2mm.

[0049] test

[0050] The coatings obtained in Examples 1 to 3 were tested for hardness and friction performance.

[0051] Before testing, the coating was wire-cut to obtain a test sample measuring 10 mm x 10 mm x 20 mm. The sample was then ground and polished. 240#, 400#, 800#, or 1200# sandpaper was used for polishing. The present invention does not require any specific polishing method; any method familiar to those skilled in the art can be used.

[0052] (1) Hardness test

[0053] The in-situ generated Ti3SiC2 reinforced Co-based coating prepared in Examples 1 to 3 was subjected to a hardness test using the Vickers hardness test method. The test load was 200 g, the loading time was 15 seconds, and the number of test points for each sample was 8. One maximum point and one minimum point were removed, and the average hardness value of the remaining points was taken. The test temperature was room temperature. The results are shown in Table 1.

[0054] Table 1 Test results of average hardness of coatings in Examples 1 to 3

[0055] performance Example 1 Example 2 Example 3 <![CDATA[Average hardness / HV 0.2 > 453.8 563.3 679.2

[0056] As shown in Table 1, at room temperature, the Ti3SiC2-reinforced Co-based coating was in situ generated by laser cladding. As the (Ti-Si-TiC) powder content increased, the average hardness of the coating was significantly improved. The average hardness of the coating in Examples 1 to 3 was as follows: Figure 2 shown.

[0057] (2) Friction performance test

[0058] The present application tests the room temperature wear performance of the in-situ generated Ti3SiC2 reinforced Co-based coatings prepared in Examples 1 to 3. Table 2 shows the test results of the friction coefficient of the coatings in Examples 1 to 3.

[0059] Table 2 Test results of friction coefficient of coating in Examples 1 to 3

[0060] performance Example 1 Example 2 Example 3 Friction coefficient 0.573 0.565 0.543

[0061] From Table 2, we can see that at room temperature, the friction coefficient of the Ti3SiC2 reinforced Co-based coating generated by laser cladding in situ decreases with the increase of (Ti-Si-TiC) powder content. The friction coefficient and wear morphology of the coatings in Examples 1 to 3 are shown in Table 2. Figure 3 、 Figure 4 shown.

[0062] The in-situ generated Ti3SiC2 reinforced Co-based coating obtained by the above method provided by the present invention has a significantly improved hardness and further improved friction performance under the cladding process of the present invention.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an in-situ generated Ti3SiC2 reinforced Co-based coating, characterized in that: The preparation method comprises: S1 prepares mixed powder: the mixed powder includes Co powder, Ti powder, Si powder and TiC powder; S2 ball-mills the mixed powder prepared in step S1 to obtain a preset composite powder; In step S3, the pre-set composite powder obtained in step S2 is clad on the surface of the substrate using a laser cladding process to obtain an in-situ generated Ti3SiC2 reinforced Co-based coating.

2. The preparation method according to claim 1, characterized in that In step S1 , the mass percentage of Co powder is 70% to 90%, the mass percentage of Ti powder is 2.45% to 7.35%, the mass percentage of Si powder is 1.43% to 4.29%, and the mass percentage of TiC powder is 6.12% to 18.36%.

3. The preparation method according to claim 2, characterized in that In step S1, the mass ratio of Co powder to the total amount of Ti powder, Si powder and TiC powder is (7-9):(1-3); the molar ratio of the Ti powder, Si powder and TiC powder is 1:1:

2.

4. The preparation method according to claim 1, characterized in that In step S1 , the purity of Co powder, Ti powder, Si powder and TiC powder is 99.0% to 99.9%, and the particle size is 100 to 200 μm.

5. The preparation method according to claim 1, characterized in that In step S2, the ball milling time is 3 to 5 hours, and the rotation speed is 150 to 240 r / min.

6. The preparation method according to claim 1, characterized in that In step S3, the substrate is 45 steel.

7. The preparation method according to claim 1, characterized in that In step S3 , the laser cladding process is specifically as follows: laser power is 0.9-1.6 kW; scanning speed is 240-300 mm / min; powder feeding amount is 20-28 g / min; and overlap rate is 35%-45%.

8. The preparation method according to claim 1, characterized in that In step S3, before the laser cladding operation is performed, the substrate surface is pre-treated.

9. The preparation method according to claim 8, characterized in that The pretreatment includes grinding, cleaning and sandblasting.

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