Laves phase reinforced heavy-load steel rail repair alloy powder

Abstract

The invention relates to a Laves phase reinforced heavy-load steel rail repair alloy powder which comprises the following raw materials: 8% of Ni, 8% of Cr, 8% of Mn, 0.1% of Ta, 0.1% of Ti, 0.1% of Nb, 0.3% of Si and the balance of Fe. According to the Fe-based powder, local plasma additive repair is conducted on the steel rail, a cladding layer formed by the cladding powder basically guarantees the original component proportion of the powder, the repair layer and a steel rail base body have good bonding performance, and the repair layer is of a fine eutectic structure and has a soft FCC phase and a hard Laves phase. Ni, Cr and Mn are used for stabilizing an FCC phase and improving the hardenability, and Ta, Ti, Nb and Si are used for forming a hard Laves phase. The FCC phase provides good plasticity and toughness, and the Laves phase can effectively improve hardness and wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of cladding materials, and in particular to a cladding material for repairing rails. Background Art

[0002] U75V rails (60 rails) are the main type of rails currently used in my country's heavy-duty freight lines. During long-term service, the rail surface and rail ends are prone to severe wear and even block loss. When the size of the damaged part reaches the overhaul range, the rails will be replaced. Replacing the rails not only affects the normal operation of the rails, but also increases maintenance costs and a lot of manpower and material resources. Therefore, it is urgent to repair them through remanufacturing methods to increase the service life of the rails and reduce maintenance costs.

[0003] Considering the short maintenance window of rails, rail repair must be completed in a short time, which requires a highly efficient repair method. Plasma additive technology has higher efficiency than laser additive technology, and can ensure the service performance of the repair layer, making it the most suitable method for on-site repair. However, there is currently no commercial grade powder suitable for rail plasma additive repair. Therefore, it is necessary to design powder suitable for U75V rail plasma repair in response to the service requirements of heavy-duty rails.

[0004] The following issues need to be considered in powder design: 1. The powder components must have high compatibility and bonding with the rail matrix.

[0005] 2. The powder needs to be self-fluxing and have good formability.

[0006] 3. The performance of the cladding layer should be limited to exceed the U75V rail to avoid accelerated wear of the wheelset. Summary of the invention

[0007] The object of the present invention is to provide a Laves phase-reinforced heavy-duty rail repair alloy powder. The Fe-based alloy powder of the present invention is used for local plasma cladding repair of rails. The repair layer has good bonding with the rail substrate. The repair layer is a fine eutectic structure with a soft FCC phase and a hard Laves phase. The role of Ni, Cr, and Mn elements is to stabilize the FCC phase and is beneficial to improving hardenability. The role of Ta, Ti, Nb, and Si is to form a hard Laves phase. The FCC phase provides better plasticity, toughness, and fatigue resistance, and the Laves phase can effectively improve strength, hardness, and wear resistance.

[0008] To achieve the above object, the present invention provides the following technical solutions: A Laves phase strengthened heavy-duty rail repair alloy powder, wherein the raw materials are composed of the following by weight percentage: Ni: 8%, Cr: 8%, Mn: 8%, Ta: 0.1%, Ti: 0.1%, Nb: 0.1%, Si: 0.3%, and the balance is Fe.

[0009] The preparation method of the powder is to mix the materials uniformly according to the proportion, and the average particle size of the powder is 80-150 μm.

[0010] The rail material is U75V.

[0011] The powder is suitable for plasma cladding, and is suitable for plasma cladding of U75V substrate. The parameters are cladding current 100A, powder feeding voltage 4 V, scanning speed 60 mm / min, and central gas flow rate 2.5 L / min.

[0012] The design principle of the powder composition of the present invention is: Ni, Cr, and Mn elements have high solubility in FCC-Fe and have strong austenite stabilization effect. At the same time, during the plasma additive solidification process, they ensure high hardenability and avoid uneven temperature and stress fields in the rail cladding layer. However, excessive addition will lead to the formation of brittle σ phase. After thermodynamic phase diagram analysis and solidification kinetics analysis, the total addition should be less than 25%. At the same time, in order to form a high entropy effect in the local microstructure, the principle of adding Ni, Cr, and Mn elements in equal proportions is adopted, and 8% is added each. The design principle is as shown in the attached Fig.10 and Fig.11 shown.

[0013] The addition of Ta, Ti, and Nb elements is mainly to form a dispersed strengthening phase in the FCC matrix. Ta, Ti, and Nb elements can form a hard Laves phase with Si elements, which has a significant strengthening effect on the FCC matrix. When the total addition amount does not exceed 0.3%, it will not cause a significant decrease in toughness and plasticity. A single Laves phase-forming element may cause segregation during the solidification process. In order to ensure the dispersed and uniform distribution of the Laves phase, Ta, Ti, and Nb are used in equal proportions with Si elements to form a hard Laves phase to ensure the fine dispersion of the precipitated phase.

[0014] There are two main reasons for adding Si element. One is that it can deoxidize and slag, and is a good deoxidizer. The other is that it forms a hard Laves phase with Ta, Ti, and Nb elements. However, if the Si content exceeds 0.35%, the plasticity and toughness of the repair layer will be reduced, so the silicon content is determined to be 0.3%.

[0015] The beneficial effects produced by adopting the above technical solution are: The Fe-based powder of the present invention is used to perform local plasma additive repair on the rail. The cladding layer formed by the cladding powder basically ensures the original composition ratio of the powder. The repair layer has good bonding with the rail matrix. The repair layer is a fine eutectic structure with a soft FCC phase and a hard Laves phase. The role of Ni, Cr, and Mn elements is to stabilize the FCC phase and is beneficial to improving hardenability. The role of Ta, Ti, Nb, and Si is to form a hard Laves phase. The FCC phase provides better plasticity, toughness, and fatigue resistance, and the Laves phase can effectively improve strength, hardness, and wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the powder of the embodiment of the present invention.

[0017] Figure 2 This is the solidification tissue simulation of the embodiment of the present invention.

[0018] Figure 3 It is the macroscopic morphology obtained under different process parameters. The macroscopic morphology obtained under the process parameters of the embodiment of the present invention is sample 9#.

[0019] Figure 4 It is the interface microstructure between the cladding layer and the substrate prepared in the embodiment of the present invention.

[0020] Figure 5 This is the microstructure morphology of the cladding layers prepared in the embodiment of the present invention.

[0021] Figure 6 This is the microstructure TEM of the cladding layer prepared in the embodiment of the present invention.

[0022] Figure 7 Graph 1 is the hardness distribution of the cladding layer and the substrate prepared in the embodiment of the present invention.

[0023] Figure 8 It is an impact sample of the cladding layer prepared in the embodiment of the present invention.

[0024] Fig. 9 It is the on-site repair of the embodiment of the present invention.

[0025] Fig.10 It is the equilibrium phase diagram of FeCrNiMn.

[0026] Fig.11 It is the rapid solidification solid phase stability of FeCrNiMn. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the following embodiments and comparative examples, the substrate is U75V rail, and the size of the repair layer is 35 mm×10 mm×3 mm (within the range of minor rail repair).

[0029] The preparation method of the powder is to mix the materials evenly according to the ratio, and the average particle size of the powder is 80-150μm. Plasma cladding technology is used to simulate the solidification process through the cellular automaton method. At the same time, combined with experiments, the process parameters are optimized, and the optimal parameters are cladding current 100 A, powder feeding voltage 4 V, scanning speed 60 mm / min, and central gas flow 2.5 L / min.

[0030] The organization of the cladding layer was analyzed by metallographic microscope, scanning electron microscope, transmission electron microscope, etc. It was found that the organization was uniform and continuous, there was no obvious metallurgical defect, the elements were evenly distributed, the interface was well bonded, the interlayer was continuously transitioned, the cladding layer was a two-phase organization composed of austenite and martensite, there was a fine hard Laves phase in the austenite, and the organization composition in the layer was uniform. The average hardness of the matrix was 370HV, and the average hardness of the repaired layer was 392HV. The hardness was continuously transitioned and evenly distributed, and the hardness of the repaired layer was slightly higher than that of the matrix. The average impact energy Ak at room temperature was 58J, and the hardness and impact performance met the standard requirements of railway rails. The repair quality met the railway industry standard TB\T1631--2002 Technical Conditions for Arc Repair of Rails. The mechanical properties are higher than the room temperature impact energy of 45J required by the railway industry standard "Technical Conditions for Ordering 43Kg / m-75Kg / m Rails" (TB / T 2344), and the Brinell hardness (HB S10 / 3000) is maintained at 330-380.

[0031] The alloy powder of the present invention was used to repair the Chidabai railway line on site, and no metallurgical defects were found after flaw detection. The actual service situation was tracked for 6 months, and no obvious wear and cracks were found, and no defects were found after flaw detection.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A Laves phase strengthened heavy-duty rail repair alloy powder, characterized in that: The raw materials are composed as follows by weight percentage: Ni: 8%, Cr: 8%, Mn: 8%, Ta: 0.1%, Ti: 0.1%, Nb: 0.1%, Si: 0.3%, and the balance is Fe.

2. The alloy powder according to claim 1, characterized in that: The material of the rail to be repaired is U75V.

3. The alloy powder according to claim 1, characterized in that: The alloy powder is used to repair the rail by plasma cladding method, and the parameters are cladding current 100 A, powder feeding voltage 4 V, scanning speed 60 mm / min, and central gas flow rate 2.5 L / min.

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