Method for refining and homogenizing NbC strengthening phase in iron-based wear-resistant coating
By adding graphene powder to an iron-based wear-resistant coating, a fine and uniformly distributed NbC reinforcing phase was prepared, which solved the wear problem caused by coarse NbC carbides in traditional alloy coatings and improved wear resistance and crack resistance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-03-27
AI Technical Summary
Traditional Fe-Cr-C alloy coatings are prone to forming coarse NbC carbides during wear, leading to accelerated wear and reduced service life. Furthermore, the morphology of NbC with high Nb content is detrimental to wear resistance and crack resistance.
By adding 0.01–0.4 wt.% graphene powder to an iron-based wear-resistant coating, using it as a high-quality carbon source, and combining it with submerged arc welding technology to prepare an NbC reinforcing phase, the coating is refined and homogenized, forming a fine and dispersed NbC distribution.
It significantly improves the wear resistance and crack sensitivity of iron-based alloy coatings, inhibits the formation of coarse NbC, and enhances the microhardness and electrical and thermal conductivity of the alloy.
Smart Images
Figure CN121732945A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating, belonging to the field of material surface technology. Background Technology
[0002] Traditional Fe-Cr-C alloy coatings are widely used in the repair of mining machinery parts due to their low cost, good processing performance, and excellent mechanical properties. However, during the coating preparation process, coarse primary M7C3 carbides are easily formed. Under wear conditions, although these coarse carbides bear the main load, they are prone to peeling off from the surface of the parts as the wear time increases, and participate in the wear of the base material as abrasive, thereby reducing the service life of the parts.
[0003] As a strong carbide-forming element, nitrogen (Nb) can combine with carbon (C) during the solidification process of the molten pool to form a high-melting-point, high-hardness NbC reinforcing phase. This phase can refine grains, improve the heat resistance of the alloy, and reduce hardenability, thereby significantly improving the wear resistance of the weld overlay alloy and its service performance in high-temperature environments. However, studies have shown that when the Nb content is too high, NbC tends to form coarse rod-shaped or bar-shaped morphologies. In addition, a large number of blocky NbC particles will also form in the coating. This type of reinforcing phase not only weakens the wear resistance of the coating but also increases crack sensitivity, limiting its further application in industrial production. Therefore, how to optimize the microstructure of the NbC reinforcing phase in iron-based alloys and thus improve their overall performance has become a key issue in improving the wear resistance of iron-based alloy coatings. Summary of the Invention
[0004] The purpose of this invention is to provide a method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating. The method achieves the refinement and homogenization of the NbC phase in the iron-based wear-resistant coating by adding graphene. The mass percentage of graphene powder in the iron-based wear-resistant coating is 0.01 to 0.4 wt.%.
[0005] Preferably, the iron-based wear-resistant coating of the present invention is prepared from the following mixed raw materials, and the raw materials and their mass percentages are as follows: ferromanganese powder 2-2.5 wt.%; Ni powder: 0.5-0.7 wt.%; ferroniobium powder: 3-6 wt.%; ferrosilicon powder: 0.5-0.8 wt.%; ferrochrome powder: 5-8 wt.%; graphene powder: 0.01-0.4 wt.%; the balance being spherical iron powder.
[0006] The spherical iron powder has a purity of 99.99%, and the Ni powder has a purity of 99.99 wt.%; the ferromanganese alloy powder composition is: Mn: 80.63 wt.%, C: 0.48 wt.%, with the balance being Fe; the ferroniobium alloy powder composition is: Nb: 66.9 wt.%, C: 0.1 wt.%, with the balance being Fe; the ferrosilicon alloy powder composition is: Si: 73.46 wt.%, C: 0.05 wt.%, with the balance being Fe; the graphene composition is: C: 99.5 wt.%; the low-carbon ferrochrome alloy powder composition is: Cr: 65.89 wt.%, C: 0.3 wt.%, with the balance being Fe.
[0007] Preferably, the iron-based wear-resistant coating of the present invention is prepared on a 60CrMnMo substrate by submerged arc welding. Before submerged arc welding, the mixed raw materials are dried and the 60CrMnMo substrate is subjected to rust removal and cleaning pretreatment.
[0008] Preferably, the drying process described in this invention is: drying at 100°C for 2 hours.
[0009] Preferably, the wire feeding speed of the submerged arc welding process of the present invention is 30m / h, the voltage is 25-30V, and the current is 300-400A.
[0010] Preferably, the interpass temperature of the submerged arc welding process of the present invention is 350-450℃.
[0011] Another objective of this invention is to provide an iron-based wear-resistant coating in which the NbC wear-resistant phase is distributed in a fine and dispersed manner; the surface of the NbC iron-based alloy wear-resistant coating prepared with graphene as a high-quality carbon source is free of cracks, and the bulk NbC is significantly reduced.
[0012] The synergistic welding of raw materials and process parameters described in this invention can significantly reduce the presence of large-sized blocky NbC particles in traditional Fe-Cr-Nb-C alloys, while refining the morphology of rod-shaped NbC precipitates. In the initial stage of wear performance testing, the large-sized blocky and rod-shaped NbC particles preferentially contact the friction pair during wear, protecting the matrix. However, as wear progresses to the middle and later stages, these large-sized blocky and rod-shaped NbC particles detach from the matrix after wear, becoming abrasive particles that further intensify wear. The refined and homogenized NbC obtained by adding graphene can effectively disperse the negative impact of load during wear, reducing stress concentration tendency and thus improving wear resistance.
[0013] The beneficial effects of this invention are: (1) During the preparation of traditional Fe-Cr-Nb-C alloys, coarse NbC precipitates are formed at the grain boundaries, which is not conducive to the improvement of wear and impact performance. Therefore, fine and uniform NbC precipitates are the key factors to improve the wear resistance of iron-based alloys. The wear-resistant coating of iron-based alloy prepared by submerged arc welding on the surface of 60CrMnMo in this invention has a fine and uniform NbC strengthening phase prepared with graphene as carbon source in the coating, which effectively suppresses the adverse behavior of coarse strengthening phases and makes the alloy coating have high microhardness, excellent wear resistance and high crack resistance.
[0014] (2) During the reaction, carbon atoms in the graphene lattice directly participate in diffusion and combine with niobium, which promotes the in-situ generation of fine and uniformly distributed NbC precipitates, effectively suppressing the segregation behavior of NbC. During the friction and wear test, the uniformly distributed precipitates can disperse the stress concentration caused by the applied load, hinder the direct wear of the friction pair on the substrate, thereby reducing the tendency of interface shedding and improving wear resistance.
[0015] (3) The NbC optimized by graphene is uniformly distributed in the matrix, which can hinder crack propagation and thus improve its toughness. In addition, graphene and iron-based alloys can produce a synergistic effect, which not only combines the high hardness and high melting point of NbC with the excellent electrical and thermal conductivity of graphene, but may also introduce new interface effects to further improve the overall performance of the material. Attached Figure Description
[0016] Figure 1 This is a metallographic image magnified 1000 times to show the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating, obtained by adding graphene powder to control the microstructure.
[0017] Figure 2 This is a scanning electron microscope (SEM) image, magnified 2000x, showing the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating, obtained by adding graphene powder to control the microstructure.
[0018] Figure 3 This is a metallographic image magnified 1000 times to show the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating, obtained by adding graphene powder to control the microstructure.
[0019] Figure 4 This is a scanning electron microscope (SEM) image at 2000x magnification, showing the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating, obtained by adding graphene powder to control the microstructure.
[0020] Figure 5The image shows the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating without the addition of graphene powder, magnified 1000 times.
[0021] Figure 6 This is a scanning electron microscope (SEM) image at 2000x magnification showing the microstructure and mechanical properties of the NbC wear-resistant phase in the iron-based wear-resistant coating without the addition of graphene powder, as described in Comparative Example 1. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.
[0023] In this embodiment of the invention, the spherical iron powder has a purity of 99.99%, the Ni powder has a purity of 99.99 wt.%, the ferromanganese alloy powder composition is: Mn: 80.63 wt.%, C: 0.48 wt.%, with the balance being Fe; the ferroniobium alloy powder composition is: Nb: 66.9 wt.%, C: 0.1 wt.%, with the balance being Fe; the ferrosilicon alloy powder composition is: Si: 73.46 wt.%, C: 0.05 wt.%, with the balance being Fe; the graphene composition is: C: 99.5 wt.%; and the low-carbon ferrochrome alloy powder composition is: Cr: 65.89 wt.%, C: 0.3 wt.%, with the balance being Fe.
[0024] Example 1 A method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating specifically includes the following steps: (1) Weigh the raw materials accurately according to the following mass percentages: 2.5 wt.% manganese iron powder; 0.5 wt.% Ni powder; 3 wt.% niobium iron powder; 0.5 wt.% silicon iron powder; 5 wt.% chromium iron powder; 0.15 wt.% graphene powder; the remainder is spherical iron powder.
[0025] (2) After mixing the iron-based alloy powder raw materials evenly, dry them at 100℃ for 2 h; the substrate is 60CrMnMo, and the surface of the substrate is derusted using 320-2000 grit sandpaper, and the surface of the substrate after derusting is cleaned with alcohol.
[0026] (3) A wear-resistant iron-based alloy coating was prepared on the substrate surface by using a submerged arc welding machine. The submerged arc welding process parameters were: wire feeding speed of 30m / h, voltage of 30V, current of 350A; and interpass temperature of 350℃.
[0027] The wear resistance of the iron-based alloy coating prepared in this embodiment was tested: pin-disc friction wear was used, with a load of 80 N and a friction rate of 120 r / min; the test sample size was 30×30×5 mm, and the friction pair was a YG6 tungsten carbide hard alloy ball with a diameter of 6.5 mm; the sample was cleaned and dried before and after the test, and then weighed by an analytical balance and the wear loss was calculated (wear loss = weight before wear - weight after wear). The accuracy of the analytical balance was 0.0001 g. The average friction coefficient of the iron-based alloy coating was measured to be 0.5198. The weight of the sample before the wear test was 67.1311 g, and the weight of the sample after the wear test was 67.1129 g. The wear amount after 1 hour of wear was 18.2 mg.
[0028] No cracks were found in the coating structure when observed with metallographic microscope and scanning electron microscope, and the NbC strengthening phase in the coating was rod-shaped and bar-shaped, with fewer dot-shaped NbC. Figure 1 The image is a 1000x metallographic image obtained after adding 0.15 wt.% graphene. Figure 2 The corresponding 2000x scanning electron microscope image is shown. Combining the two images, it can be seen that the number of large NbC particles in the coating after adding graphene is significantly reduced, and the remaining precipitated phase is refined and homogenized. The wear resistance of the coating in this embodiment is significantly improved compared with Comparative Example 1 without graphene.
[0029] Example 2 A method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating specifically includes the following steps: (1) Weigh the raw materials accurately according to the following mass percentages: 2.5 wt.% manganese iron powder; 0.5 wt.% Ni powder; 3 wt.% niobium iron powder; 0.5 wt.% silicon iron powder; 5 wt.% chromium iron powder; 0.3 wt.% graphene powder; the remainder is spherical iron powder.
[0030] (2) After mixing the iron-based alloy powder raw materials evenly, dry them at 100℃ for 2 h; the substrate is 60CrMnMo, and the surface of the substrate is derusted using 320-2000 grit sandpaper, and the surface of the substrate after derusting is cleaned with alcohol.
[0031] (3) A wear-resistant iron-based alloy coating was prepared on the substrate surface by using a submerged arc welding machine. The submerged arc welding process parameters were: wire feeding speed of 30m / h, voltage of 28V, current of 300A; and interpass temperature of 450℃.
[0032] The wear resistance of the iron-based alloy coating prepared in this embodiment was tested using the same method as in Example 1. The average friction coefficient of the iron-based alloy coating was measured to be 0.6311. The weight of the sample before the wear test was 67.0579 g, and the weight of the sample after the wear test was 67.0469 g. The wear amount after 1 hour of wear was 11 mg.
[0033] Metallographic microscopy and scanning electron microscopy revealed no cracks in the coating microstructure. The number of rod-shaped and bar-shaped NbC reinforcing phases in the coating was significantly reduced, while the number of dot-shaped NbC phases increased, indicating that the precipitated phases were significantly refined. In addition, the number of large-sized blocky NbC phases in the coating was further reduced.
[0034] Figure 3 The image shows a 1000x metallographic view obtained after adding 0.3 wt.% graphene. Figure 4 The images are 2000x scanning electron microscope (SEM) images. Combining the two images, it can be seen that the large-sized blocky NbC particles in the optimized coating with added graphene are significantly reduced, and the remaining NbC precipitates are also significantly refined. Many dot-shaped NbC particles are uniformly distributed in the matrix within the coating. During wear performance testing, the coarse NbC precipitates, after detaching during the middle and later stages of wear, participate in the wear of the matrix, exacerbating the wear behavior. However, the NbC refined and homogenized by graphene can withstand greater loads without detaching, greatly improving wear behavior and enhancing the wear resistance of the coating. Therefore, the coating refined and homogenized with 0.3 wt.% graphene exhibits the best wear resistance.
[0035] Example 3 A method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating specifically includes the following steps: (1) Weigh the raw materials accurately according to the following mass percentages: 2.5 wt.% manganese iron powder; 0.5 wt.% Ni powder; 3 wt.% niobium iron powder; 0.5 wt.% silicon iron powder; 5 wt.% chromium iron powder; 0.05 wt.% graphene powder; the remainder is spherical iron powder.
[0036] (2) After mixing the iron-based alloy powder raw materials evenly, dry them at 100℃ for 2 h; the substrate is 60CrMnMo, and the surface of the substrate is derusted using 320-2000 grit sandpaper, and the surface of the substrate after derusting is cleaned with alcohol.
[0037] (3) A wear-resistant iron-based alloy coating was prepared on the substrate surface by using a submerged arc welding machine. The submerged arc welding process parameters were: wire feeding speed of 30m / h, voltage of 28V, current of 300A; and interpass temperature of 450℃.
[0038] The wear resistance of the iron-based alloy coating prepared in this embodiment was tested.
[0039] The average friction coefficient of the iron-based alloy coating was measured to be 0.7833. The weight of the sample before the wear test was 67.4621 g, and the weight of the sample after the wear test was 67.4333 g. The wear amount after 1 hour of wear was 28.8 mg. The mass loss of this example is significantly improved compared with the comparative example 1 without graphene, that is, the wear resistance is significantly improved.
[0040] Comparative Example 1 A method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating specifically includes the following steps: Weigh the raw materials accurately according to the following mass percentages: ferromanganese powder 2.5 wt.%; Ni powder: 0.7 wt.%; ferroniobium powder: 4 wt.%; ferrosilicon powder: 0.5 wt.%; ferrochrome powder: 5 wt.%; the balance is spherical iron powder.
[0041] The iron-based alloy powder raw materials were mixed evenly and dried at 100℃ for 2 h. The substrate was 60CrMnMo. Rust was removed from the substrate surface using 320-2000 grit sandpaper, and the surface was cleaned with alcohol. A submerged arc welding machine was used to prepare a wear-resistant iron-based alloy coating on the substrate surface. The submerged arc welding process parameters were: wire feed speed of 30 m / h, voltage of 30 V, current of 350 A; and interpass temperature of 400℃.
[0042] The wear resistance of the iron-based alloy coating prepared in this embodiment was tested using the same method as in Example 1: the average friction coefficient of the iron-based alloy coating was measured to be 0.7670, the weight of the sample before the wear test was 68.4763 g, the weight of the sample after the wear test was 68.4351 g, and the wear amount after 1 hour of wear was 41.2 mg.
[0043] No cracks were found in the coating microstructure observed using metallographic microscopy and scanning electron microscopy. The NbC reinforcing phase in the coating was rod-shaped and rod-shaped, and there were large areas of blocky NbC.
[0044] Figure 5 A 1000x metallographic image was prepared for comparison experiments; Figure 6 The corresponding 2000x scanning electron microscope image is shown. Combining the two images, it can be seen that there are large areas of blocky and elongated NbC in the coating. These large-sized precipitates are prone to stress concentration and detachment during wear, which aggravates the wear behavior. Therefore, the coating of this comparative example has a higher coefficient of friction and the greatest mass loss, indicating that the coating prepared in this comparative example has poor wear resistance.
[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating, characterized in that: The NbC phase in the iron-based wear-resistant coating is refined and homogenized by adding graphene. The mass percentage of graphene powder in the iron-based wear-resistant coating is 0.01 to 0.4 wt.%.
2. The method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating according to claim 1, characterized in that: The iron-based wear-resistant coating is prepared from the following mixed raw materials, and the raw materials and their mass percentages are as follows: ferromanganese powder 2-2.5 wt.%; Ni powder 0.5-0.7 wt.%; ferroniobium powder 3-6 wt.%; ferrosilicon powder 0.5-0.8 wt.%; ferrochrome powder 5-8 wt.%; graphene powder 0.01-0.4 wt.%; the balance is spherical iron powder.
3. The method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating according to claim 2, characterized in that: The iron-based wear-resistant coating is prepared on a 60CrMnMo substrate using a submerged arc welding process. Before submerged arc welding, the mixed raw materials are dried, and the 60CrMnMo substrate is subjected to rust removal and cleaning pretreatment.
4. The method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating according to claim 3, characterized in that: The drying process involves drying at 100°C for 2 hours.
5. The method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating according to claim 3, characterized in that: The wire feeding speed of the submerged arc welding process is 30m / h, the voltage is 25-30V, and the current is 300-400A.
6. The method for refining and homogenizing the NbC reinforcing phase in an iron-based wear-resistant coating according to claim 5, characterized in that: The interpass temperature for submerged arc welding is 350-450℃.
7. The iron-based wear-resistant coating prepared by the method according to any one of claims 1 to 6, characterized in that: The NbC wear-resistant phase is distributed in the coating in a fine, dispersed manner.