激光熔覆AlCoCrFeNiSix高熵合金涂层的微观组织及耐蚀性能

Microstructure and Corrosion Resistance of AlCoCrFeNiSix High-entropy Alloy Coating by Laser Cladding

摘要:

利用激光熔覆技术在AISI 304不锈钢表面制备了AlCoCrFeNiSix（x=0.1，0.2，0.3，0.4，0.5）高熵合金涂层。采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、能谱分析仪（EDS）、透射电子显微镜（TEM）、维氏硬度计和电化学工作站等，分析了Si元素对AlCoCrFeNiSix高熵合金涂层微观组织和性能的影响。结果表明：AlCoCrFeNiSix高熵合金涂层由体心立方（BCC）固溶体晶粒构成。随着Si元素含量的增加，Si元素置换固溶使晶格收缩，晶粒逐步细化，纳米尺度球状AlNi相在晶粒内脱溶，少量的Cr23C6碳化物沿晶界析出。微观组织的演化导致涂层的显微硬度升高，最大硬度达到848.1 HV0.3。AlCoCrFeNiSix高熵合金涂层的热力学腐蚀倾向和均匀腐蚀速率均低于基材AISI 304不锈钢。Si元素的掺杂提高了钝化膜的修复能力和稳定性，使腐蚀机制从自催化发展的点蚀转变为晶间腐蚀。

Abstract:

AlCoCrFeNiSix(x=0.1，0.2，0.3，0.4，0.5) high-entropy alloy coatings were prepared on the surface of AISI 304 stainless steel. The effect of Si element on the microstructure and properties of the high-entropy alloy was investigated using X-ray diffractometer (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS), transmission electron microscope (TEM), Vickers hardness tester, and electrochemical workstation. The results show that the high-entropy alloy coatings consist of solid-solution grains with body-centered cubic (BCC) lattice. With the increase of the Si element content, the substitutional solid solution of Si element causes the crystal lattice to shrink, and the crystal grains are gradually refined. Besides, the AlNi phase with nano-scale spherical shape is dissolved in the crystal grains, and a small amount of Cr23C6 carbides are precipitated along the grain boundaries. The evolution of the microstructure leads to an increase in the microhardness of the coating, with the maximum hardness reaching 848.1 HV0.3. The thermodynamic corrosion tendency and uniform corrosion rate of AlCoCrFeNiSix high-entropy alloy coating are lower than the AISI 304 stainless steel. The doping of Si element improves the repair ability and stability of the passivation film, and promotes the corrosion mechanism to transform from pitting corrosion developed by autocatalysis to intergranular corrosion.