高速激光熔覆对CoCrFeNiMo_(0.2)高熵合金组织及耐蚀性的影响

Effect of high-speed laser cladding on microstructure and corrosion resistance of CoCrFeNiMo_(0.2) high-entropy alloy

在提高生产效率的同时,获得较强CoCrFeNiMo_(0.2)高熵合金(HEA)的耐蚀性,采用高速激光熔覆(HLC)技术制备了CoCrFeNiMo_(0.2)高熵合金涂层。以优化后的HLC工艺参数(激光功率880W、扫描速度18 m/min、搭接率60%、送粉速度3 r/min)制备了本文中的涂层。分别对涂层的表面粗糙度、微观结构、相组成、元素分布进行了分析,并且在3.5 wt%NaCl溶液中采用三电极体系进行了电化学试验,对HLC和传统激光熔覆(CLC)的CoCrFeNiMo_(0.2)高熵合金涂层的耐蚀性能进行测试和分析。试验结果表明:HLC技术制备的CoCrFeNiMo_(0.2)高熵合金涂层的表面粗糙度为15.53μm,涂层中为单一的FCC相,在涂层与基体之间通过线扫描能谱分析可以观察到明显的冶金结合,涂层自底部到顶部的微观组织依次为平面晶、胞状组织、柱状树枝晶和等轴树枝晶。电化学测试结果表明,与CLC涂层相比,HLC技术制备的CoCrFeNiMo_(0.2)高熵合金涂层表现出明显的钝化效果。采用Tafel外推法计算了HLC涂层的自腐蚀电流密度为5.4411×10^(-6)A·cm^(-2)、自腐蚀电位为-0.7445 V,CLC涂层的自腐蚀电流密度和自腐蚀电位分别为2.7083×10^(-5)A·cm^(-2)和-0.9685 V。HLC技术制备的CoCrFeNiMo_(0.2)高熵合金涂层表现出优越的耐蚀性,主要是由于其表面微观组织为均匀细小的晶粒。HLC技术可推广应用于各种复杂恶劣的工作条件下的耐腐蚀工件修复以及再制造领域。

In order to study the corrosion resistance of high-speed laser cladding(HLC) coating while improving production efficiency,a CoCrFeNiMo_(0.2)high-entropy alloy(HEA) coating was prepared by HLC.The optimized parameters of HLC are laser power of 880 W,scanning speed of 18 m/min,overlapping ratio of 60%,and powder feed speed of 3 r/min.Then,the surface roughness,microstructure,phase composition,element distribution,and electrochemical properties in 3.5 wt% NaCl solution of the coatings were analyzed,respectively.The local surface roughness of the CoCrFeNiMo_(0.2)HEA coating was found to be 15.53 μm.A distinct metallurgical bond could be observed between the coating and the substrate.Compared to the conventional laser cladding(CLC),the results of electrochemical tests showed that CoCrFeNiMo_(0.2)HEA coating exhibited a significant passivation.The corrosion current density of 5.4411 × 10^(-6)A·cm^(-2) and the corrosion potential of-0.7445 V for the HLC coating were calculated by the Tafel extrapolation method.The CLC coating’s corrosion current density and corrosion potential are 2.7083×10^(-5)A·cm^(-2) and-0.9685 V,respectively.The HLC coating shows a superior corrosion resistance,crucially due to the uniform and fine grains.Under various complex and harsh working conditions,this method can be widely used in the field of repairing and remanufacturing of corro sion-proof workpiece s.