Stainless steel composite powder and preparation method and application thereof

Abstract

The application provides a stainless steel composite powder and a preparation method and application thereof, and the stainless steel composite powder comprises the following preparation raw materials in percentage by weight: 70.8-90.2% of stainless steel powder, 2-6% of chromium powder, 2-5% of molybdenum powder, 0.3-1.2% of graphite powder, 1-3% of vanadium powder, 0.5-2% of niobium powder, 1-2% of silicon powder and 3-10% of copper-yttrium oxide composite modified titanium carbide; the method for preparing the copper-yttrium oxide composite modified titanium carbide comprises the following steps: S1, mixing titanium carbide and yttrium oxide with polyvinylpyrrolidone, and then performing ball milling to obtain a first mixture; mixing copper salt, a complexing agent and water, and then heating to obtain a second mixture; S2, mixing the first mixture, the second mixture and a reducing agent, and then heating to react. The stainless steel composite powder can improve the wear resistance and hardness of a cladding layer.

Description

Technical Field

[0001] This application relates to the field of powder metallurgy technology, and in particular to a stainless steel composite powder, its preparation method and application. Background Technology

[0002] Gray cast iron brake discs are widely used in automotive braking systems due to their excellent thermal conductivity and vibration damping properties. However, the wear resistance and hardness of traditional gray cast iron brake discs are no longer sufficient to meet current requirements.

[0003] Laser cladding is a surface treatment technology that uses a high-energy laser beam to heat the surface of a substrate, causing the cladding material to form a metallurgical bond with the substrate. In recent years, ultra-high-speed laser cladding (EHLA), as a major innovation in laser cladding technology, has received widespread attention. Previous studies have used EHLA technology to prepare a composite coating of 316L stainless steel and 16% TiC on gray cast iron brake discs, achieving a 44.4% reduction in wear mass loss at room temperature compared to the original substrate.

[0004] While titanium carbide possesses high hardness and is an ideal hard reinforcing phase, its wettability with the iron matrix is ​​poor. Current techniques typically involve directly and mechanically mixing titanium carbide with metal powder for cladding. However, under the cyclic shear stress of braking friction, titanium carbide particles are prone to peeling or detachment, making it difficult to fully realize its hard reinforcing effect.

[0005] Studies have shown that the addition of appropriate amounts of La2O3 can effectively improve the microstructure and properties of laser cladding layers, refining the microstructure and reducing cracks; the addition of appropriate amounts of CeO2 can refine TiC particles and improve the relative density of the coating; the addition of Y2O3 can significantly improve the forming quality of composite coatings, greatly reducing cracks and porosity. However, existing technologies typically add rare earth oxides to powders through mechanical mixing. Because rare earth oxides are nano- or submicron-sized particles with large specific surface areas and high surface energies, they are prone to agglomeration and uneven distribution during mixing, making it difficult to fully realize their potential for refining the microstructure and reducing cracks, thus limiting the improvement of the wear resistance and hardness of the cladding layer. Summary of the Invention

[0006] The present invention is made in view of the above-mentioned problems, and its purpose is to provide a stainless steel composite powder, a method for preparing the same, and its application, wherein the stainless steel composite powder can improve the wear resistance and hardness of the cladding layer.

[0007] Specifically, the first aspect of the present invention provides a stainless steel composite powder comprising the following raw materials in weight percentage: stainless steel powder: 70.8%–90.2%, chromium powder: 2%–6%, molybdenum powder: 2%–5%, graphite powder: 0.3%–1.2%, vanadium powder: 1%–3%, niobium powder: 0.5%–2%, silicon powder: 1%–2%, and copper-yttrium oxide composite modified titanium carbide: 3%–10%. The method for modifying titanium carbide with copper-yttrium oxide composite includes the following steps: S1. Titanium carbide, yttrium oxide and polyvinylpyrrolidone are mixed and then ball-milled to obtain the first mixture; A second mixture is prepared by mixing copper salt, complexing agent and water and heating. S2 is prepared by mixing the first mixture, the second mixture, and the reducing agent and then heating the mixture to react.

[0008] Optionally, the total molar ratio of the graphite powder to the vanadium powder and the niobium powder is 1:0.8 to 1.2.

[0009] Optionally, in step S1, the mass ratio of titanium carbide, yttrium oxide and polyvinylpyrrolidone is 100:(0.05-2):(0.3-1.5).

[0010] Optionally, the heating temperature in step S1 is 50°C to 70°C.

[0011] Optionally, the complexing agent in step S1 is potassium tartrate.

[0012] Optionally, the reducing agent in step S2 is hypophosphite.

[0013] Optionally, the heating temperature in step S2 is 70°C to 80°C.

[0014] Optionally, the solid-liquid ratio of the first mixture to the second mixture in step S2 is 20 g / L to 40 g / L.

[0015] Optionally, the mass ratio of copper salt to potassium tartrate salt in step S1 is 1:(2-4).

[0016] Optionally, the mass ratio of copper salt in step S1 to hypophosphite in step S2 is 1:(1-2.5).

[0017] A second aspect of the present invention provides a method for preparing stainless steel composite powder, comprising the following steps: ball milling and mixing the raw materials, drying and sieving.

[0018] Optionally, the ball milling speed is 150 rpm to 250 rpm.

[0019] Optionally, the ball milling mixing time is 2h to 4h.

[0020] Optionally, the drying temperature is 60°C to 80°C.

[0021] A third aspect of the present invention provides an application of stainless steel composite powder on a brake disc, wherein the stainless steel composite powder forms a cladding layer on the surface of the brake disc after being subjected to ultra-high-speed laser cladding.

[0022] Optionally, the brake disc is a gray cast iron brake disc.

[0023] Optionally, the laser power of the ultra-high-speed laser cladding is 3.5kW to 5.5kW.

[0024] Optionally, the scanning speed of the ultra-high-speed laser cladding is 40m / min to 75m / min.

[0025] Optionally, the powder feeding rate of the ultra-high-speed laser cladding is 20 g / min to 35 g / min.

[0026] Optionally, the positive defocusing amount of the ultra-high-speed laser cladding is 8mm to 12mm.

[0027] Optionally, the overlap rate of the ultra-high-speed laser cladding is 65% to 75%.

[0028] Compared with the prior art, the present invention has the following beneficial effects: In the process of ultra-high-speed laser cladding, the copper-yttrium oxide composite modified titanium carbide provided by this invention undergoes instantaneous partial melting of the Cu phase, which effectively improves the wettability between the ceramic phase and the metal matrix; at the same time, Y2O3 is uniformly dispersed based on the TiC particle skeleton, which fully exerts the effect of refining grains.

[0029] This invention uses stainless steel powder as the matrix, adds copper-yttrium oxide composite modified titanium carbide as an external reinforcing phase, and introduces vanadium powder and niobium powder to form VC and NbC hard phases with graphite powder, so that the hardness of the cladding layer formed by ultra-high speed laser cladding of stainless steel composite powder reaches 484 HV. 0.3 ~518HV 0.3 The coefficient of friction is controlled within the range of 0.384 to 0.425. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a SEM image of the cladding layer formed by the stainless steel composite powder prepared in Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0033] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0034] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0035] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0036] The particle size range of the 430L stainless steel powder in the embodiments and comparative examples of this invention is 15μm to 53μm; The particle size range of chromium powder, molybdenum powder, vanadium powder, silicon powder, niobium powder, and titanium carbide is 10μm to 20μm. The particle size range of yttrium oxide is 20 nm to 50 nm; The graphite powder is in flake form with an average particle size of 5 μm. Polyvinylpyrrolidone was purchased from Henan Pengfei New Material Co., Ltd., with a K value of 15.5, N-vinylpyrrolidone content ≤0.1%, and nitrogen content of 12.1%.

[0037] Example 1 The stainless steel composite powder provided in this embodiment has the following mass percentages of raw materials: 430L stainless steel powder: 86%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.5%, vanadium powder: 1.5%, niobium powder: 0.8%, silicon powder: 1.2%, and copper-yttrium oxide composite modified titanium carbide: 5%.

[0038] The total molar ratio of graphite powder to vanadium powder and niobium powder is 1:0.91; The preparation method of copper-yttrium oxide composite modified titanium carbide in this embodiment consists of the following steps: Titanium carbide powder, yttrium oxide powder and polyvinylpyrrolidone were mixed and then ball-milled at 250 rpm for 3 hours with anhydrous ethanol as the medium and a ball-to-material ratio of 5:1 to obtain yttrium oxide modified titanium carbide.

[0039] Dissolve potassium sodium tartrate in water at 60°C, then add copper sulfate pentahydrate, and finally add sodium hypophosphite. Stir to prepare a chemical copper plating solution.

[0040] Yttrium oxide-modified titanium carbide was mixed with a chemical copper plating solution at a solid-liquid ratio of 30 g / L. The mixture was stirred at 200 rpm for 45 min in a 75°C water bath, then naturally cooled to 25°C. The solid phase was collected, washed, and vacuum dried at 60°C for 6 h to obtain copper-yttrium oxide composite modified titanium carbide.

[0041] The mass ratio of titanium carbide powder, yttrium oxide powder and polyvinylpyrrolidone is 100:2:0.8. The mass ratio of copper sulfate, potassium sodium tartrate, and sodium hypophosphite is 1:2.8:1.5.

[0042] The preparation method of stainless steel composite powder in this embodiment is as follows: The raw materials for preparing the stainless steel composite powder were mixed and ball-milled at 180 rpm for 2.5 h under argon protection with anhydrous ethanol as the medium and a ball-to-material ratio of 2:1. The ball-milled slurry was then vacuum-dried at -0.08 MPa and 70 °C for 5 h. The dried composite powder was then sieved through 270 mesh and 1000 mesh sieves to obtain the stainless steel composite powder.

[0043] The method for preparing the cladding layer in this embodiment is as follows: Using gray cast iron brake discs as the base material, after surface degreasing and rust removal treatment, the surface is preheated to 300℃. Stainless steel composite powder is then clad onto the brake disc surface using ultra-high-speed laser cladding technology, forming a 0.2mm cladding layer. During the cladding process, high-purity argon gas (flow rate 15L / min) is used as the protective gas, with a laser power of 4.5kW, a scanning speed of 60m / min, a positive defocusing amount of 10mm, a powder feeding rate of 30g / min, and an overlap rate of 70%.

[0044] Figure 1This is a SEM image of the cladding layer formed by the stainless steel composite powder prepared in Example 1. The image shows that the granular phase is uniformly and diffusely distributed on the substrate surface. The particle morphology is close to spherical, and the overall dispersion is good, with no obvious agglomeration.

[0045] Example 2 The stainless steel composite powder provided in this embodiment differs from that in Embodiment 1 in that: The mass percentages of the raw materials used in the preparation are as follows: 430L stainless steel powder: 88%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.5%, vanadium powder: 1.5%, niobium powder: 0.8%, silicon powder: 1.2%, and copper-yttrium oxide composite modified titanium carbide: 3%.

[0046] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0047] Example 3 The stainless steel composite powder provided in this embodiment differs from that in Embodiment 1 in that: The raw materials include the following weight percentages: 430L stainless steel powder: 81%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.5%, vanadium powder: 1.5%, niobium powder: 0.8%, silicon powder: 1.2%, and copper-yttrium oxide composite modified titanium carbide: 10%.

[0048] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0049] Example 4 The stainless steel composite powder provided in this embodiment differs from that in Embodiment 1 in that: The mass percentages of the raw materials used in the preparation are as follows: 430L stainless steel powder: 85.93%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.57%, vanadium powder: 1.5%, niobium powder: 0.8%, silicon powder: 1.2%, and copper-yttrium oxide composite modified titanium carbide: 5%.

[0050] The total molar ratio of graphite powder to vanadium powder and niobium powder is 1:0.8; The mass ratio of titanium carbide, yttrium oxide and polyvinylpyrrolidone is 100:0.5:0.3.

[0051] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0052] Example 5 The stainless steel composite powder provided in this embodiment differs from that in Embodiment 1 in that: The mass percentages of the raw materials used in the preparation are as follows: 430L stainless steel powder: 86.12%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.38%, vanadium powder: 1.5%, niobium powder: 0.8%, silicon powder: 1.2%, and copper-yttrium oxide composite modified titanium carbide: 5%.

[0053] The total molar ratio of graphite powder to vanadium powder and niobium powder is 1:1.2; The mass ratio of titanium carbide, yttrium oxide and polyvinylpyrrolidone is 100:2:1.5.

[0054] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0055] Comparative Example 1 The stainless steel composite powder provided in this comparative example differs from that in Example 1 in the following ways: Replace copper-yttrium oxide composite modified titanium carbide with copper-modified titanium carbide.

[0056] The preparation method of copper-modified titanium carbide is as follows: Dissolve potassium sodium tartrate in water at 60°C, then add copper sulfate pentahydrate, and finally add sodium hypophosphite. Stir to prepare a chemical copper plating solution.

[0057] Titanium carbide was mixed with electroless copper plating solution at a solid-liquid ratio of 30 g / L. The mixture was stirred at 200 rpm for 45 min in a water bath at 75 °C, and then naturally cooled to 25 °C. The solid phase was collected, washed, and dried under vacuum at 60 °C for 6 h to obtain copper-modified titanium carbide.

[0058] The mass ratio of copper sulfate, potassium sodium tartrate, and sodium hypophosphite is 1:2.8:1.5.

[0059] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0060] Comparative Example 2 The stainless steel composite powder provided in this comparative example differs from that in Example 1 in the following ways: Replace copper-yttrium oxide composite modified titanium carbide with yttrium oxide modified titanium carbide.

[0061] The preparation method of yttrium oxide modified titanium carbide is as follows: Titanium carbide powder, yttrium oxide powder and polyvinylpyrrolidone were mixed and then ball-milled at 250 rpm for 3 hours with anhydrous ethanol as the medium and a ball-to-material ratio of 5:1 to obtain yttrium oxide modified titanium carbide.

[0062] The mass ratio of titanium carbide powder, yttrium oxide powder and polyvinylpyrrolidone is 100:2:0.8.

[0063] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0064] Comparative Example 3 The stainless steel composite powder provided in this comparative example differs from that in Example 1 in the following ways: The mass percentages of the raw materials used in the preparation are as follows: 430L stainless steel powder: 91%, chromium powder: 2.5%, molybdenum powder: 2.5%, graphite powder: 0.5%, vanadium powder: 1.5%, niobium powder: 0.8%, and silicon powder: 1.2%.

[0065] The total molar ratio of graphite powder to vanadium powder and niobium powder is 1:0.91.

[0066] The preparation methods for stainless steel composite powder and cladding layer are as described in Example 1.

[0067] The performance of the cladding layers formed by the stainless steel composite powders prepared in Examples 1-5 and Comparative Examples 1-3 was evaluated.

[0068] (1) Friction coefficient: A pin-disc friction and wear tester was used. The grinding material was GCr15 steel ball, the load was 50N, the sliding speed was 0.2m / s, the sliding distance was 500m, and the friction coefficient was recorded.

[0069] (2) Microhardness: A Vickers hardness tester was used with a load of 300g and a holding time of 15s. Five different locations were selected for testing each sample, and the average value was taken as the hardness value of the sample.

[0070] The evaluation results of various properties of the cladding layers formed by the stainless steel composite powders prepared in Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0071] Table 1. Evaluation results of various properties of the cladding layers formed by the stainless steel composite powders prepared in Examples 1-5 and Comparative Examples 1-3.

[0072] As can be seen from Table 1, the hardness of the cladding layer formed by the stainless steel composite powder prepared in Examples 1-5 reaches 484 HV. 0.3 ~518HV 0.3 The coefficient of friction is controlled within the range of 0.384 to 0.425.

[0073] Compared to Example 1, the hardness of Example 2 decreased by 29 HV. 0.3 The friction coefficient increased by 0.038, which may be due to the reduced content of hard reinforcing phase in the cladding layer, weakening the dispersion strengthening effect and the load-bearing and friction-reducing effect of hard particles.

[0074] Compared to Example 1, the hardness of Example 3 decreased by 14 HV. 0.3The friction coefficient increased by 0.009, which may be due to the local agglomeration that occurred during the cladding process when the amount of reinforcing phase increased to 10%, causing micro-defects and resulting in a slight decrease in hardness. However, the sufficient reinforcing phase still maintained good wear resistance.

[0075] Compared to Example 1, the hardness of Example 4 decreased by 23 HV. 0.3 The friction coefficient increased by 0.017, which may be due to the low total molar ratio of graphite powder to vanadium powder and niobium powder, and the reduced proportion of yttrium oxide, which hindered the precipitation of hard carbides and reduced the interfacial bonding strength.

[0076] Compared to Example 1, the hardness of Example 5 decreased by 34 HV. 0.3 The friction coefficient increased by 0.041, which may be due to the increased total amount of graphite powder, vanadium powder, and niobium powder, the reduced amount of graphite powder added, the relative lack of carbon, and the less precipitation of hard carbides, resulting in a weakened dispersion strengthening effect and a decrease in both hardness and wear resistance.

[0077] Compared with Example 1, the hardness of Comparative Example 1 decreased by 11.4% and the coefficient of friction increased by 17.7%. This may be due to the lack of yttrium oxide modification, which prevented the effective improvement of the shape and distribution of titanium carbide particles, resulting in insufficient refinement of the internal structure of the cladding layer and a decrease in both hardness and wear resistance.

[0078] Compared with Example 1, Comparative Example 2 showed a 15.8% decrease in hardness and a 26.3% increase in friction coefficient. This may be due to the lack of copper interface modification, which reduced the interfacial wettability and bonding strength between titanium carbide and the iron matrix. The reinforcing phase was prone to peeling off during friction, exacerbating abrasive wear.

[0079] Compared with Example 1, Comparative Example 3 showed a 22.2% decrease in hardness and a 38% increase in friction coefficient. This may be due to the absence of copper-yttrium oxide composite modified titanium carbide as a key hard reinforcing phase, resulting in a lack of dispersed ceramic particles in the cladding layer for dispersion reinforcement. The matrix mainly relies on solid solution reinforcement of alloying elements, resulting in a single reinforcement mechanism and a significant decrease in overall hardness. At the same time, due to the lack of anti-abrasive wear support from the high-hardness reinforcing phase, the cladding layer is more prone to adhesion and plowing wear during friction, leading to a significant increase in the friction coefficient.

[0080] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A stainless steel composite powder, characterized in that, The raw materials include the following weight percentages: stainless steel powder: 70.8%–90.2%, chromium powder: 2%–6%, molybdenum powder: 2%–5%, graphite powder: 0.3%–1.2%, vanadium powder: 1%–3%, niobium powder: 0.5%–2%, silicon powder: 1%–2%, and copper-yttrium oxide composite modified titanium carbide: 3%–10%. The method for modifying titanium carbide with copper-yttrium oxide composite includes the following steps: S1. Titanium carbide, yttrium oxide and polyvinylpyrrolidone are mixed and then ball-milled to obtain the first mixture; A second mixture is prepared by mixing copper salt, complexing agent and water and heating. S2 is prepared by mixing the first mixture, the second mixture, and the reducing agent and then heating the mixture to react.

2. The stainless steel composite powder according to claim 1, characterized in that, The total molar ratio of the graphite powder to the vanadium powder and the niobium powder is 1:0.8 to 1.

2.

3. The stainless steel composite powder according to claim 1, characterized in that, In step S1, the mass ratio of titanium carbide, yttrium oxide and polyvinylpyrrolidone is 100:(0.05-2):(0.3-1.5).

4. The stainless steel composite powder according to claim 1, characterized in that, The heating temperature in step S1 is 50℃~70℃; And / or, the complexing agent in step S1 is potassium tartrate; And / or, the reducing agent in step S2 is hypophosphite; And / or, the heating temperature in step S2 is 70°C to 80°C; And / or, in step S2, the solid-liquid ratio of the first mixture to the second mixture is 20 g / L to 40 g / L.

5. The stainless steel composite powder according to claim 4, characterized in that, In step S1, the mass ratio of copper salt to potassium tartrate salt is 1:(2-4).

6. The stainless steel composite powder according to claim 4, characterized in that, The mass ratio of copper salt in step S1 to hypophosphite in step S2 is 1:(1-2.5).

7. A method for preparing stainless steel composite powder as described in any one of claims 1 to 6, characterized in that, The process includes the following steps: ball milling and mixing the raw materials, drying and sieving.

8. The method for preparing stainless steel composite powder according to claim 7, characterized in that, The ball milling speed is 150 rpm to 250 rpm; And / or, the ball milling mixing time is 2h to 4h; And / or, the drying temperature is 60°C to 80°C.

9. An application of the stainless steel composite powder as described in any one of claims 1 to 6 on a brake disc, characterized in that, The stainless steel composite powder forms a cladding layer on the surface of the brake disc after being clad by ultra-high-speed laser.

10. The application of the stainless steel composite powder according to claim 9 on brake discs, characterized in that, The brake disc is a gray cast iron brake disc; And / or, the laser power of the ultra-high-speed laser cladding is 3.5kW to 5.5kW; And / or, the scanning speed of the ultra-high-speed laser cladding is 40m / min to 75m / min; And / or, the powder feeding rate of the ultra-high-speed laser cladding is 20g / min to 35g / min; And / or, the positive defocusing amount of the ultra-high-speed laser cladding is 8mm to 12mm; And / or, the overlap rate of the ultra-high-speed laser cladding is 65% to 75%.

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