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.

Description

BACKGROUNDTechnical Field[0001]The present disclosure belongs to the field of material processing, and particularly relates to a method for efficiently preparing a metal cladded coating on a rail surface by laser and auxiliary heat source hybrid cladding. The method can improve the wear resistance and contact fatigue performance of the rail, solve the problems of poor railway shunt, and repair the damaged rail.Description of Related Art[0002]China's rail transit has developed rapidly, and by the end of 2016, the national railway operation mileage has reached 124,000 kilometers. With the increase of railway transportation volume, train speed and axle load, damage problems such as rail wear, rolling contact fatigue and rail corrosion of rails are becoming more and more prominent. The damage of the rail mainly occurs on the surface, and thus, the preparation of the coating on the surface of the rail is of great significance for extending its service life.[0003]Thermal spraying, electro...

AI Technical Summary

Benefits of technology

The present disclosure provides a method for efficiently preparing a high-performance cladded coating on a rail surface using a laser and auxiliary heat source hybrid cladding to reinforce and repair the rail surface. The method avoids generation of cracks and harmful structures in the heat-affected zone and ensures that mechanical properties between the cladded coating, the heat-affected zone, and the rail substrate are well matched. The method can be used for improving wear resistance and contact fatigue performance of the rail, as well as solving problems of poor railway shunt and damaged rails. The method further involves reasonably regulating a temperature cycle curve of the heat-affected zone under laser action to meet critical conditions of complete transformation from austenite to pearlite and allow the heat-affected zone to be transformed into a fine lamellar pearlite structure which has good mechanical properties and overall fatigue performance.

Problems solved by technology

With the increase of railway transportation volume, train speed and axle load, damage problems such as rail wear, rolling contact fatigue and rail corrosion of rails are becoming more and more prominent.

The welding layer and the rail substrate are metallurgically bonded, but in this method, the heat input and heat-affected zone are large, resulting in that the microstructure and performance uniformity of the surfacing layer are poor, and the martensite structure is easily induced inside the rail substrate.

However, with the rapid heating and rapid cooling effect of the laser, high-carbon acicular martensite structure may be generated in the heat-affected zone of the rail.

The martensite structure has high hardness, but low toughness, which may easily cause the rail breakage.

In addition, since the cladded coating and the heat-affected zone have a high cooling rate and a large temperature gradient relative to the rail substrate at a high laser scanning rate, cracks may be easily generated in the cladded coating and the heat-affected zone, which affects the safe service of the train.

However, this method does not consider how to reduce and avoid the martensite phase transformation in the heat-affected zone when preparing a cladded coating on a large high-carbon steel substrate (such as a rail), as well as technical problems such as matching of mechanical properties of the cladded coating, the heat-affected zone and the substrate in a specific service environment (rolling rail contact).

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