METHOD FOR REINFORCING RAIL BY LASER AND AUXILIARY HEAT SOURCE EFFICIENT HYBRID CLADDING

Abstract

The disclosure discloses a method for reinforcing a rail by laser and auxiliary heat source efficient hybrid cladding. The laser and the auxiliary heat source simultaneously apply on a region to be cladded of a rail surface. The laser serves as a main heat source to enable simultaneous and rapid fusion of an added metal powder and partial substrate material in the rail surface to form a molten pool. The auxiliary heat source moves with the laser heat source in the same direction at the same speed, and performs synchronous preheating and/or post-heating on the laser molten pool, the heat-affected zone and the surface layer of the rail substrate to reduce the temperature gradient, thereby reducing the cooling rate, and avoiding martensite transformation and cracking in the heat-affected zone.

Claims

1. A method for reinforcing a rail by laser and auxiliary heat source efficient hybrid cladding, wherein in the method, a laser and an auxiliary heat source are utilized to simultaneously apply on a region to be cladded of a rail surface; the laser serves as a main heat source to enable rapid fusion of an added powder material and a partial substrate material on the rail surface to form a molten pool and then to form a cladded coating; the auxiliary heat source is located in front of or/and behind the main heat source, moves with the main heat source in the same direction at the same speed, and performs synchronous preheating and/or post-heating on the molten pool, a heat-affected zone and a surface layer of a rail substrate to reduce a temperature gradient between the molten pool and heat-affected zone and the rail substrate, thereby reducing a cooling rate of the molten pool and heat-affected zone, and avoiding martensite transformation in the laser-heat-affected zone and generation of cracks in the cladded coating and the heat-affected zone at a high laser scanning rate.

2. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein a thermal cycle process of the heat-affected zone under laser action is reasonably regulated by the combined action of the laser and the auxiliary heat source such that a cooling time of the heat-affected zone is larger than a critical cooling time of transformation from austenite to pearlite in a continuous cooling transformation (CCT) curve or a time-temperature-transformation (TTT) curve, thereby meeting critical conditions of complete transformation from austenite to pearlite, and allowing the heat-affected zone to be transformed into a fine lamellar pearlite structure which has an interlamellar spacing less than or equal to that of the rail substrate and has a hardness between hardnesses of the cladded coating and the rail substrate, so that mechanical properties between the cladded coating, the heat-affected zone and the rail substrate are reasonably matched, the hardness curve is smooth, and the overall fatigue performance is good.

3. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the auxiliary heat source adopts any one of induction heating, oxyacetylene flame and propane torch, or any combination thereof.

4. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein a preheating temperature is 100-1000 C., and a post-heating temperature is 300-700 C.

5. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the cladded coating obtained by single processing has a thickness of 0.1-2 mm, a width of 3-20 mm, and a hardness which is controlled within a range of HV250 to HV500 according to specific requirements of the rail.

6. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the heat-affected zone has a width of less than 1 mm and a hardness of HV250 to HV400, and there is no martensite transformation in the heat-affected zone.

7. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the method comprises following specific implementation steps of: (1) polishing the region to be cladded of the rail surface first to remove surface rust and contaminants; (2) adjusting a defocusing distance of a laser beam to allow a laser spot to be a circular spot with a diameter of 3-20 mm or a rectangular spot with a size of (1-3) mm(6-30) mm; (3) adjusting relative position of the laser spot and the auxiliary heat source such that the laser spot is in front of, in the middle of or behind the auxiliary heat source; (4) turning on the laser and the auxiliary heat source, and synchronously feeding or pre-placing a coating material into a laser irradiation region of the rail surface by using an automatic powder feeder, so that the molten pool is formed when the focused laser beam is incident on the rail substrate, and then the cladded coating is formed on the rail surface after the molten pool is solidified, wherein the auxiliary heat source plays a role of preheating and/or post-heating the rail, with a preheating temperature of 100-1000 C. and a post-heating temperature of 300-700 C.; (5) after a layer of the cladded coating is formed, determining whether a thickness of the cladded coating meets working conditions, and if so, ending the cladding process; if not, repeating the above steps (2), (3) and (4) until the thickness requirements are met; (6) after the cladding process is finished, inspecting the surface of the corrosion-resistant cladded coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating; and (7) selectively performing cleaning and profile trimming on a rail tread to make its surface flat.

8. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the method is integrated with a fixed processing platform to perform off-line processing of the rail, or integrated with an on-line mobile laser processing vehicle to perform on-line laser cladding reinforcement or repair of the rail at a railway site.

9. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 3, wherein the induction heating is implemented by an induction power supply and an induction coil; wherein the induction coil is formed by bending and welding a copper tube, a magnet is embedded on the copper tube in a working area, a lower surface of the copper tube is parallel to a cladded surface of the rail, with a gap of 0.5-15 mm; a heating zone on the rail surface has a linear structure, which is parallel to a longitudinal direction of the rail and has a length of 10-500 mm.

10. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 1, wherein the added powder material is an iron-based alloy, main chemical compositions of which are: 0.01-0.60% C, 10-40% Cr, 5-18% Ni, 0.1-3.0% Si, 0-3% B, 0-3% Mo, 1-3% Mn and Fe balance; or the added powder material is a nickel-based alloy or a cobalt-based alloy, wherein main chemical compositions of the nickel-based alloy are: 0.01-0.50% C, 20-30% Cr, 5-10% W, 3-5% Si, 0-3% B, 5-10% Fe and Ni balance; and main chemical compositions of the cobalt-based alloy are: 0.01-0.5% C, 20-35% Cr, 1-10% Ni, 1-3% Si, 5-15% W, 0-3% B, 0.5-2% Mn and Co balance.

11. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the auxiliary heat source adopts any one of induction heating, oxyacetylene flame and propane torch, or any combination thereof.

12. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein a preheating temperature is 100-1000 C., and a post-heating temperature is 300-700 C.

13. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the cladded coating obtained by single processing has a thickness of 0.1-2 mm, a width of 3-20 mm, and a hardness which is controlled within a range of HV250 to HV500 according to specific requirements of the rail.

14. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the heat-affected zone has a width of less than 1 mm and a hardness of HV250 to HV400, and there is no martensite transformation in the heat-affected zone.

15. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the method comprises following specific implementation steps of: (1) polishing the region to be cladded of the rail surface first to remove surface rust and contaminants; (2) adjusting a defocusing distance of a laser beam to allow a laser spot to be a circular spot with a diameter of 3-20 mm or a rectangular spot with a size of (1-3) mm(6-30) mm; (3) adjusting relative position of the laser spot and the auxiliary heat source such that the laser spot is in front of, in the middle of or behind the auxiliary heat source; (4) turning on the laser and the auxiliary heat source, and synchronously feeding or pre-placing a coating material into a laser irradiation region of the rail surface by using an automatic powder feeder, so that the molten pool is formed when the focused laser beam is incident on the rail substrate, and then the cladded coating is formed on the rail surface after the molten pool is solidified, wherein the auxiliary heat source plays a role of preheating and/or post-heating the rail, with a preheating temperature of 100-1000 C. and a post-heating temperature of 300-700 C.; (5) after a layer of the cladded coating is formed, determining whether a thickness of the cladded coating meets working conditions, and if so, ending the cladding process; if not, repeating the above steps (2), (3) and (4) until the thickness requirements are met; (6) after the cladding process is finished, inspecting the surface of the corrosion-resistant cladded coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating; and (7) selectively performing cleaning and profile trimming on a rail tread to make its surface flat.

16. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the method is integrated with a fixed processing platform to perform off-line processing of the rail, or integrated with an on-line mobile laser processing vehicle to perform on-line laser cladding reinforcement or repair of the rail at a railway site.

17. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 11, wherein the induction heating is implemented by an induction power supply and an induction coil; wherein the induction coil is formed by bending and welding a copper tube, a magnet is embedded on the copper tube in a working area, a lower surface of the copper tube is parallel to a cladded surface of the rail, with a gap of 0.5-15 mm; a heating zone on the rail surface has a linear structure, which is parallel to a longitudinal direction of the rail and has a length of 10-500 mm.

18. The method for reinforcing the rail by laser and auxiliary heat source efficient hybrid cladding according to claim 2, wherein the added powder material is an iron-based alloy, main chemical compositions (by weight percentage) of which are: 0.01-0.60% C, 10-40% Cr, 5-18% Ni, 0.1-3.0% Si, 0-3% B, 0-3% Mo, 1-3% Mn and Fe balanc; or the added powder material is a nickel-based alloy or a cobalt-based alloy, wherein main chemical compositions (by weight percentage) of the nickel-based alloy are: 0.01-0.50% C, 20-30% Cr, 5-10% W, 3-5% Si, 0-3% B, 5-10% Fe and Ni balance; and main chemical compositions (by weight percentage) of the cobalt-based alloy are: 0.01-0.5% C, 20-35% Cr, 1-310% Ni, 1-3% Si, 5-15% W, 0-3% B, 0.5-2% Mn and Co balance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a top view showing laser and induction post-heating hybrid cladding on a rail surface in a case where the laser spot is located in front of induction heating.

[0029] FIG. 2 is a top view showing laser, induction preheating and induction post-heating hybrid cladding on a rail surface in a case where the laser spot is located in the middle of induction heating.

[0030] FIG. 3 is a top view showing laser, induction heating and oxyacetylene flame (or laser, induction heating and propane torch) heating hybrid cladding on a rail surface.

[0031] FIG. 4 is a top view showing laser and oxyacetylene flame (or laser and propane torch) heating hybrid cladding on a rail surface.

[0032] FIG. 5 is a hardness distribution diagram along the depth direction of a rail with a

[0033] Fe-based metal cladded coating prepared by laser and induction post-heating hybrid cladding.

[0034] FIG. 6 is a hardness distribution diagram along the depth direction of a rail with a Ni-based metal cladded coating prepared by laser, induction preheating and induction post-heating hybrid cladding.

[0035] FIG. 7 is a hardness distribution diagram along the depth direction of a rail with a Co-based metal cladded coating prepared by laser, induction heating and oxyacetylene flame (or laser, induction heating and propane torch) heating hybrid cladding.

[0036] FIG. 8 is a hardness distribution diagram along the depth direction of a rail with a Fe-based metal cladded coating prepared by laser and oxyacetylene flame (or laser and propane torch) heating hybrid cladding.

[0037] In the figures: 1, laser spot; 2, induction heating coil; 2(a), induction preheating coil; 2(b), induction post-heating coil; and 3, oxyacetylene flame (or propane torch).

DESCRIPTION OF THE EMBODIMENTS

[0038] For clear understanding of the objectives, features and advantages of the present disclosure, detailed description of the present disclosure will be given below in conjunction with accompanying drawings and specific embodiments. It should be noted that the embodiments described herein are only meant to explain the present disclosure, and not to limit the scope of the present disclosure. Furthermore, the technical features related to the embodiments of the disclosure described below can be mutually combined if they are not found to be mutually exclusive.

[0039] In the present disclosure, a laser is used as a main heat source to deposit an alloy material on a surface of a rail, and an auxiliary heat source preheats or/and post-heats the rail to reduce the cooling rate of the cladded coating and the heat-affected zone, so that a functional coating with wear resistance, fatigue resistance and corrosion resistance can be efficiently prepared on the rail surface, or the damaged rail can be repaired. The thickness of the cladded coating obtained in a single processing is 0.1-2 mm, and the hardness can be adjusted in a range of HV250 to HV500 according to the specific requirements of the rail. Meanwhile, by adopting the technical route proposed by the present disclosure, martensite is not generated in the heat-affected zone of the rail, and the mechanical properties of the cladded coating and the rail substrate are reasonably matched, so that the rail has better bending fatigue and contact fatigue performance while being reinforced and repaired. The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0040] The present disclosure provides a method for reinforcing a rail by using laser and auxiliary heat source hybrid cladding, in which the auxiliary heat source may adopt induction heating, oxyacetylene flame, propane torch or a combination of induction heating and oxyacetylene flame (or propane torch). The present method can be integrated with fixed laser processing equipment to perform off-line processing on a rail, or integrated with a vehicle-mounted laser processing platform to perform on-line reinforcement or repair on a rail at the railway site. The implementation steps include the following.

[0041] (1) Polish a region to be cladded of a rail surface to remove surface rust and contaminants.

[0042] (2) Adjust the defocusing distance of a laser beam to allow a laser spot to be circular with a diameter of 3-20 mm or rectangular with a size of (1-3) mm(6-30) mm.

[0043] (3) Adjust the relative position of the laser spot and the auxiliary heat source so that the laser spot is in front of, in the middle of or behind the auxiliary heat source.

[0044] (4) Turn on the laser and auxiliary heat source, and synchronously feed (or place in advance) the alloy powder material into the laser irradiation region of the rail surface by using an automatic powder feeder, so that a molten pool is formed when the focused laser beam irradiates on the rail substrate, and then a metal coating is formed on the rail surface after the molten pool is solidified; the auxiliary heat source acts on the rail for preheating and/or post-heating, with a preheating temperature of 100-1000 C. and a post-heating temperature of 300-700 C.

[0045] (5) After a layer of metal cladded coating is formed, determine whether the thickness of the cladded coating meets working conditions, and if so, end the cladding process; if not, repeat the above steps (2), (3) and (4) until the thickness requirements are met.

[0046] (6) After the cladding process is finished, inspect the surface of the corrosion-resistant cladded coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating.

[0047] (7) According to application requirements, selectively perform cleaning and profile trimming on the rail tread to make the surface flat, thereby obtaining a finished product.

[0048] Embodiment 1: on-line laser and induction post-heating efficient hybrid cladding at the railway site

[0049] In this embodiment, the service rail is efficiently reinforced or repaired at the railway site, in which induction heating acts as an auxiliary heat source, and an industrial manipulator or a three-dimensional motion axis is used as a machining motion and position control unit. A region to be cladded of a rail surface is heated with the heating temperature and time controlled by an induction heating device and a temperature control part. The induction heating device includes an induction power supply and an induction coil, and the temperature control part includes an infrared thermometer and a temperature controller, in which the induction coil is connected to the induction power supply, the infrared thermometer is connected to the temperature controller, and the temperature controller is connected to the induction power supply via a data line. A detection signal of the infrared thermometer is input to the temperature controller, and after calculation, the temperature controller outputs a control signal to adjust the output power of the induction heating power supply to achieve the control of the induction heating temperature of the rail. The laser spot is focused on the front of the induction coil, as shown in FIG. 1. Basic implementation steps for preparing a metal cladded coating on a rail surface by laser and induction post-heating hybrid cladding are as follows.

[0050] (1) Select iron-based alloy powder as cladding material, the main chemical compositions (Wt. %) of which are: (0.01-0.60) C, (10-40) Cr, (5-18) Ni, (0.1-3.0) Si, (0-3) B, (0-3) Mo, (1-3) Mn and Fe balance.

[0051] (2) Polish a region to be cladded of a rail surface to remove surface rust and contaminants.

[0052] (3) Adjust the position of the induction coil such that its lower surface is parallel to the region to be cladded of the rail surface with a gap of 5 mm; the infrared thermometer is targeted at the induction heating region of the rail surface, the infrared thermometer is connected to the temperature controller and the induction power supply to detect and control the induction heating temperature; the induction heating temperature is set to 700 C.

[0053] (4) Adjust the defocusing distance of a laser beam and the relative position of the laser spot and the induction coil such that the laser spot is focused on a rail surface in front of the induction coil; the laser spot is a circular spot with a diameter of 3 mm, the powder feed rate of a powder feeder is 10 g/min, the laser power is 1 kW, and the laser scanning speed is 0.4 m/min.

[0054] (5) Turn on a motion control unit, the laser and the induction heating power supply, and synchronously feed (or pre-place) the cladding material into the laser irradiation region of the rail surface by using an automatic powder feeder, so that a molten pool is formed when the focused laser beam is incident on the rail substrate, and then a metal cladded coating is formed on the rail surface after the molten pool is solidified.

[0055] (6) After a layer of cladded coating is formed, determine whether the thickness of the cladded coating meets working conditions, and if so, end the cladding process; if not, repeat the above steps (2), (3), (4) and (5) until the thickness requirements are met.

[0056] (7) After the cladding process is finished, inspect the surface of the metal coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating.

[0057] (8) According to application requirements, selectively perform cleaning and profile trimming on the rail tread to make the surface flat, thereby obtaining a finished product.

[0058] In this embodiment, the thickness of the prepared iron-based metal cladded coating is 0.1 mm, the mechanical properties between the cladded coating, the heat-affected zone and the rail substrate are reasonably matched, and the hardness distribution along the rail depth direction is as shown in FIG. 5.

[0059] Embodiment 2: on-line laser, induction preheating and induction post-heating efficient hybrid cladding at the railway site

[0060] In this embodiment, the service rail is efficiently reinforced or repaired at the railway site, in which induction heating acts as an auxiliary heat source, the induction heating control part is the same as that in Embodiment 1, and an industrial manipulator or a three-dimensional motion axis is used as a machining motion and position control unit. The laser spot is focused in the middle of the induction coil, as shown in FIG. 2. Basic implementation steps for preparing a metal cladded coating on a rail surface by laser, induction preheating and induction post-heating hybrid cladding are as follows.

[0061] (1) Select nickel-based alloy powder as cladding material, the main chemical compositions (Wt. %) of which are: (0.01-0.50) C, (20-30) Cr, (5-10) W, (3-5) Si, (0-3) B, (5-10) Fe and Ni balance.

[0062] (2) Polish a region to be cladded of a rail surface to remove surface rust and contaminants.

[0063] (3) Adjust the position of the induction coil such that the lower surface is parallel to the region to be cladded of the rail surface with a gap of 0.5 mm; the infrared thermometer is targeted at the induction heating region of the rail surface, and the infrared thermometer is connected to the temperature controller and the induction power supply to detect and control the induction heating temperature; the induction heating temperature is set to 500 C.

[0064] (4) Adjust the defocusing distance of a laser beam and the relative position of the laser spot and the induction coil such that the laser spot is focused on a rail surface in front of the induction coil; the laser spot is a rectangular spot with a size of 16 mm, the powder feed rate of a powder feeder is 50 g/min, the laser power is 5 kW, and the laser scanning speed is 2 m/min.

[0065] (5) Turn on a motion control unit, the laser and the induction heating power supply, and synchronously feed (or pre-place) the cladding material into the laser irradiation region of the rail surface by using an automatic powder feeder, so that a molten pool is formed when the focused laser beam is incident on the rail substrate, and then a metal cladded coating is formed on the rail surface after the molten pool is solidified.

[0066] (6) After a layer of cladded coating is formed, determine whether the thickness of the cladded coating meets working conditions, and if so, end the cladding process; if not, repeat the above steps (2), (3), (4) and (5) until the thickness requirements are met.

[0067] (7) After the cladding process is finished, inspect the surface of the metal coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating.

[0068] (8) According to application requirements, selectively perform cleaning and profile trimming on the rail tread to make the surface flat, thereby obtaining a finished product.

[0069] In this embodiment, the induction coil consists of two parts: 4(a) and 4(b) connected by a copper tube, in which 4(a) plays a role of preheating the rail, and 4(b) plays a role of delaying the cooling rate of the rail. In practical applications, under the premise of reasonable matching of mechanical properties, the cladding efficiency can be effectively improved, which is conducive to energy conservation. The thickness of the prepared nickel-based metal cladded coating is 0.5 mm, the mechanical properties between the cladded coating, the heat-affected zone and the rail substrate are reasonably matched, and the hardness distribution along the rail depth direction is as shown in FIG. 6.

[0070] Embodiment 3: off-line laser, induction heating and oxyacetylene flame (or propane torch) heating efficient hybrid cladding on a rail surface

[0071] In this embodiment, off-line reinforcement or repair is performed on the rail, in which induction heating and oxyacetylene flame (or propane torch) act as the auxiliary heat source. The laser spot is focused in front of the induction coil, and the oxyacetylene flame (or propane torch) preheats a rail surface to be cladded, as shown in FIG. 3. The laser and the induction coil move in the same direction at the same speed, and the induction heating synchronously preheats the laser molten pool and the heat-affected zone of the rail. The basic implementation steps are as follows:

[0072] (1) Select cobalt-based alloy powder as cladding material, the main chemical compositions (Wt. %) of which are: (0.01-0.5) C, (20-35) Cr, (1-10) Ni, (1-3) Si, (5-15) W, (0-3) B, (0.5-2) Mn and Co balance.

[0073] (2) Polish a region to be cladded of a rail surface to remove surface rust and contaminants.

[0074] (3) Adjust the position of the induction coil such that the lower surface is parallel to the region to be cladded of the rail surface with a gap of 15 mm; the infrared thermometer is targeted at the induction heating region of the rail surface, and the infrared thermometer is connected to the temperature controller and the induction power supply to detect and control the induction heating temperature; the induction heating temperature is set to 300 C.

[0075] (4) Adjust the defocusing distance of a laser beam and the relative position of the laser spot and the induction coil so that the laser spot is focused on a rail surface in front of the induction coil; the laser spot is a rectangular spot with a size of 330 mm, the powder feed rate of a powder feeder is 250 g/min, the laser power is 20 kW, and the laser scanning speed is 30 m/min.

[0076] (5) Preheat the region to be cladded of the rail surface with oxyacetylene flame/propane torch, in which the infrared thermometer 6-2 is aimed at the heated region of the rail surface to monitor the preheating temperature, and when the preheating temperature reaches 100-200 C., the oxyacetylene flame/propane torch device is closed.

[0077] (6) Turn on the laser and the induction heating power supply, and synchronously feed (or pre-place) the cladding material into the laser irradiation region of the rail surface by using an automatic powder feeder, so that a molten pool is formed when the focused laser beam is incident on the rail substrate, and then a metal cladded coating is formed on the rail surface after the molten pool is solidified.

[0078] (7) After a layer of cladded coating is formed, determine whether the thickness of the cladded coating meets working conditions, and if so, end the cladding process; if not, repeat the above steps (2), (3), (4), (5) and (6) until the thickness requirements are met.

[0079] (8) After the cladding process is finished, inspect the surface of the metal coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating.

[0080] (9) According to application requirements, selectively perform cleaning and profile trimming on the rail tread to make the surface flat, thereby obtaining a finished product.

[0081] In this embodiment, the thickness of the prepared cobalt-based metal cladded coating is 0.2 mm, the mechanical properties between the cladded coating, the heat-affected zone and the rail substrate are reasonably matched, and the hardness distribution along the rail depth direction is as shown in FIG. 7.

[0082] Embodiment 4: off-line laser and oxyacetylene flame (or propane torch) heating efficient hybrid cladding on a rail surface

[0083] In this embodiment, off-line reinforcement and repair is performed on the rail, in which oxyacetylene flame (or propane torch) is selected as an auxiliary heat source. As shown in FIG. 4, basic implementation steps for preparing a metal cladded coating on a rail surface by laser and oxyacetylene flame (or laser and propane torch) hybrid cladding are as follows.

[0084] (1) Select iron-based alloy powder as cladding material, the main chemical compositions (Wt. %) of which are: (0.01-0.60) C, (10-40) Cr, (5-18) Ni, (0.1-3.0) Si, (0-3) B, (0-3) Mo, (1-3) Mn and Fe balance.

[0085] (2) Polish a region to be cladded of a rail surface to remove surface rust and contaminants.

[0086] (3) adjust parameters such that the laser beam is circular with a diameter of 20 mm, the laser power is 15 kW, the powder feed rate of a powder feeder is 180 g/min, and the laser scanning speed is 10 m/min.

[0087] (4) Preheat the region to be cladded of the rail surface with oxyacetylene flame/propane torch, in which the infrared thermometer is aimed at the heated region of the rail surface and monitors the preheating temperature of the rail surface to be 800-1000 C.

[0088] (5) Turn on the laser, and synchronously feed (or pre-place) the alloy powder material into the laser irradiation region of the rail surface by using an automatic powder feeder, so that a molten pool is formed when the focused laser beam is incident on the rail substrate, and then a metal cladded coating is formed on the rail surface after the molten pool is solidified; meanwhile, perform post-heating on the cladded region of the rail surface with the oxyacetylene flame/propane torch at a post-heating temperature of 300-400 C. (monitored by the infrared thermometer), and turn off the oxyacetylene flame/propane torch after a certain holding time.

[0089] (6) After a layer of cladded coating is formed, determine whether the thickness of the cladded coating meets working conditions, and if so, end the cladding process; if not, repeat the above steps (3), (4) and (5) until the thickness requirements are met.

[0090] (7) After the cladding process is finished, inspect the surface of the metal coating by penetration or ultrasonic inspection, to ensure that there are no metallurgical defects in the cladded coating.

[0091] (8) According to application requirements, selectively perform cleaning and profile trimming on the rail tread to make the surface flat, thereby obtaining a finished product.

[0092] In this embodiment, the thickness of the prepared iron-based metal cladded coating is 2 mm, the mechanical properties between the cladded coating, the heat-affected zone and the rail substrate are reasonably matched, and the hardness distribution along the rail depth direction is as shown in FIG. 8.

[0093] It should be readily understood to those skilled in the art that the above description is only preferred embodiments of the present disclosure, and does not limit the scope of the present disclosure. Any change, equivalent substitution and modification made without departing from the spirit and scope of the present disclosure should be included within the scope of the protection of the present disclosure.