公路建筑用铝合金表面激光熔覆FeCoNiCr高熵合金涂层的组织与抗腐蚀性

Microstructure and Corrosion Resistance of Laser-Cladded FeCoNiCr High-Entropy Alloy Coating on Aluminum Alloys for Highway Architecture Applications

采用激光熔覆技术在铝合金表面制备FeCoNiCr高熵合金涂层,研究该涂层的冶金质量、相结构、组织与电化学行为。结果表明:当扫描速度为10 mm/s、激光功率300 W时,容易产生未熔合主导的涂层缺陷;400 W时可以得到高致密的涂层,致密度高达99.6%;而500 W时则导致气孔主导的涂层缺陷。当扫描速度为20 mm/s时,不同激光功率的样品则产生以凝固裂纹为主的冶金缺陷。对致密的FeCoNiCr高熵合金涂层(扫描速度10 mm/s,激光功率400 W)进行了组织表征及电化学测试,结果表明,FeCoNiCr高熵合金涂层呈单相面心立方固溶体结构,以柱状晶组织为主。晶粒内部存在大量的凝固胞状亚结构,但是激光熔覆过程中,极高的冷却速度抑制了凝固过程的元素偏析,Fe、Co、Ni、Cr均匀分布。极化曲线分析表明,与铝合金基体相比,FeCoNiCr高熵合金涂层具有更高的腐蚀电位及更低的腐蚀电流密度,表现出优异的抗腐蚀性能。

Laser cladding was used to deposit FeCoNiCr high-entropy alloy coating on the aluminum alloy substrate,and the metallurgical quality,phase structure,microstructure and electrochemical behavior were investigated.The results showed that when the scan speed was 10 mm/s;a laser power of 300 W easily produced lackof-fusion dominated coating defects,a laser power of 400 W achieved highly dense coatings,with the densification of 99.6%;whereas a laser power of 500 W led to the formation of gas pores dominated coating defects.When the laser power was 20 mm/s,the coatings deposited at various laser powers were dominated by solidification cracks.The microstructural characterization and electrochemical testing were performed on the dense FeCoNiCr high-entropy alloy coating(scan speed 10 mm/s,laser power 400 W),and the results showed that the FeCoNiCr high-entropy alloy has a single-phase face-centered-cubic structure,and the grain structure was dominated by columnar grains.Within the grains,numerous solidification cell substructures existed,and Fe,Co,Ni,and Cr were uniformly distributed due to the ultrahigh cooling rate and the prohibited solidification segregation kinetics.Polarization curves showed that as compared with the aluminum alloy substrate,FeCoNiCr high-entropy alloy coating exhibited a higher corrosion potential and a lower corrosion current density,and hence an improved corrosion resistance.