激光熔覆 FeCoCrNiMn 高熵合金涂层的工艺探索

Laser cladding is an advanced surface modification technology, which can significantly improve the strength, thermal stability, radiation resistance, wear resistance, corrosion resistance and other properties of the matrix. Due to the complexity of laser cladding parameters and the direct impact on the quality of coatings, the traditional trial-and-error method used to explore the optimal cladding process parameters often affects the test process due to the shortcomings of high cost and low efficiency. The work aims to optimize the laser cladding process parameters of FeCoCrNiMn high-entropy alloy coatings based on the orthogonal test method, so as to improve the wear resistance and corrosion resistance of the coatings. 304 stainless steel (10 mm×10 mm×5 mm) was selected as the coating matrix. Before cladding, the matrix was ground with SiC sandpaper. FeCoCrNiMn high-entropy alloy powder (purity ≥99.9%, 45-105 µm, spherical powder) was selected as the coating material. During the cladding process, the laser power (600, 800, 1 000 W), scanning speed (6, 7, 8 mm/s), powder feeding rate (17, 21, 25 g/min), lap rate 50%, and defocus amount 30 mm were adopted. After ground and polished, the cladding coating was corroded with aqua regia solution (HNO₃/HCL volume ratio is 1∶3) for 15 s. The microstructure of the coating was observed by light microscopy (Axio Scope A1) and scanning electron microscope (TESCAN MIRA3). The reciprocating friction and wear testing machine (Tribo_Studio) was used to investigate the tribological properties of the coating, and the MT-500 three-dimensional profiler was used to measure the size of the wear marks and calculate the wear rate. An electropotentiostat (DH7000C) was used to test the potentiodynamic polarization curve of the coating. The prepared FeCoCrNiMn coating has a single FCC structure. From the interface bonding zone to the coating surface, the microstructure changes from continuous columnar to equiaxed. The laser power is the main affecting factor of coating quality, the A1 coating has fine microstructure grains due to low laser power (600 W), fast cooling rate, short grain growth time, the microhardness increases with grain refinement (maximum value is 190HV0.3), and the coating shows the best wear resistance (wear rate is only 0.897×10⁻⁵ mm³·N⁻¹·m⁻¹). The corrosion resistance of the FeCoCrNiMn coating increases with the increase of laser power, and the A9 coating (1 000 W) has the largest capacitive arc radius and exhibits excellent corrosion resistance, with the lowest self-corrosion current density (0.705×10⁻⁶ A/cm²) and the highest self-corrosion potential (−0.227 V). Through range analysis, the optimal process parameters are determined as follows: laser power 600 W, scanning speed 6 mm/s, and powder feeding rate 25 g/min. The microstructure and properties of the coating can be significantly improved by laser cladding technology, and the performance of the FeCoCrNiMn high-entropy alloy coating prepared under the optimal process parameters has been greatly improved, and the coating hardness (217.1HV0.3) increases by 26.8% compared with that of the A6 coating (171.2HV0.3).