| The rapid development of high-speed railway provides important support for promoting the coordinated development of China’s regions and accelerating the process of urbanization and industrialization.As the core component of the basic braking device of high-speed train,the brake disc plays an important role in the safety and reliability of the train.However,due to the continuous influence of operating conditions,excessive wear such as abnormal wear and scratches frequently occur on the brake disc of high-speed trains,resulting in early failure,which poses a serious challenge to traffic safety and operation and maintenance efficiency.Laser remanufacturing coating technology can realize the repair and reuse of damaged brake discs because it is easy to form a good metallurgical bond with the substrate and has a small heat affected zone and excellent coating performance.The Co-based alloy has excellent high temperature strength and stability,and is more suitable for laser remanufacturing of damaged brake disc cladding materials.Therefore,the use of laser cladding Co-based coating to repair the worn brake disc of high-speed trains can effectively improve the performance of the brake disc and prolong the service life of the brake disc,which is of great significance to alleviate the severe operation and maintenance situation of high-speed trains.In this paper,Co-based alloy powder was used as cladding material,and Co-based coating was prepared on the surface of high-speed train wear brake disc by laser cladding technology to repair the damaged brake disc.The effects of laser cladding process parameters on the microstructure and properties of Co-based cladding layer and interface fusion zone were systematically studied by means of optical microscope,scanning electron microscope,tensile and shear performance testing machine,nano-indenter,high temperature friction and wear testing machine,and the tribological properties and wear mechanism of Co-based cladding layer at high temperature were explored.The results show that:（1）As the laser energy density increases from 60 J·mm-3 to 120 J·mm-3,the number of pores in the Co-based cladding layer decreases first and then increases.Under the laser energy density of 80 J·mm-3 and 90 J·mm-3,no obvious pores are found in the Co-based cladding layer.The hardness and tensile strength of the Co-based cladding layer reach the maximum when the laser energy density is 90 J·mm-3,the scanning speed is 900 mm/s,and the power is195 W.This is because under this process parameter,the number of equiaxed grains in the cobalt-based cladding layer is the largest,the grains are finer,and the mechanical properties are better.（2）When the laser energy density is 80 and 90 J·mm-3,the width of the interface fusion zone changes with the change of the scanning speed,and obvious element diffusion occurs,indicating that the cladding layer and the brake disc damage surface form a good metallurgical bonding.When the laser energy density is 90 J·mm-3,the scanning speed is 900mm/s,and the power is 195 W,the nano-hardness,tensile strength and shear strength of the interface fusion zone are the best,and the bonding performance is the best.（3）The friction coefficient characteristic curve of Co-based cladding layer under different temperature conditions is more stable than that of brake disc matrix.The average friction coefficient and wear rate of Co-based cladding layer at high temperature are lower than those of brake disc matrix.The wear mechanism of Co-based cladding layer at high temperature is mainly adhesive wear,while the wear mechanism of brake disc at high temperature is mainly fatigue wear and oxidation wear.The Co-based cladding layer shows better oxidation resistance and wear resistance than the brake disc substrate at high temperature,which can effectively prolong the service life of the brake disc. |
PDF Full Text Request