激光熔覆CoCrFeNiSi_(x)高熵合金涂层组织及耐蚀性能研究

Study on Microstructure and Corrosion Resistance of CoCrFeNiSi_(x) High-entropy Alloy Coating by Laser Cladding

目的研究Si含量对CoCrFeNi系高熵合金涂层组织、物相、显微硬度及耐蚀性能的影响。方法通过激光熔覆技术在45钢基材上制备CoCrFeNiSi_(x)(x为物质的量之比,x=0.0,0.5,1.0,1.5,2.0)高熵合金涂层,使用扫描电镜、X射线衍射仪、显微硬度仪、电化学工作站对涂层的显微组织、物相组成、显微硬度、耐蚀性能、腐蚀形貌进行分析研究。结果CoCrFeNi高熵合金涂层为单一的fcc相,之后随着Si含量的提升,涂层向bcc相转变,当x=2.0时,全部转化为bcc相。涂层的微观组织以等轴晶与枝晶为主,当Si含量较少时,Si元素主要在晶界中偏析,随着Si含量的增加,过多的Si会固溶到晶粒内部。涂层的平均显微硬度随着Si含量的升高而增加,CoCrFeNiSi_(2.0)可达到566.5HV0.5。在3.5%NaCl溶液中,涂层的腐蚀电位随Si含量的增加而变大,CoCrFeNiSi_(2.0)较CoCrFeNiSi0.0的腐蚀电位正移约160 mV,腐蚀电流密度从1.17×10^(-6)A/cm^(2)减小到6.06×10^(-7)A/cm^(2),耐蚀性提高。当Si含量较低时,涂层表面出现连续大面积腐蚀痕迹,随着Si含量的增加,表面腐蚀以点蚀为主。结论在CoCrFeNi系高熵合金涂层中添加Si元素,可以促进bcc相的生成,提高涂层的显微硬度,同时可以有效抑制合金涂层的腐蚀倾向,以及减缓合金涂层的腐蚀速率,提高耐蚀性能。

The work aims to study the effect of Si content on the structure,phase,microhardness and corrosion resistance of CoCrFeNi high-entropy alloy coating.In the study,CoCrFeNiSi_(x)(x=0.0,0.5,1.0,1.5,2.0)high-entropy alloy coating on 45 steel substrate is prepared by laser cladding technology,and the phase composition,microstructure,microhardness,corrosion resistance and corrosion morphology of the coating is analyzed by using scanning electron microscope,X-ray diffractometer,micro hardness tester,electrochemical workstation.Theoretical analysis combined with experimental verification shows that the CoCrFeNi high-entropy alloy coating is a single fcc phase.The microstructure of the coating is dominated by equiaxed crystals and dendrites.When the Si content is small,the Si element is mainly segregated in the grain boundaries.As the Si content increases,too much Si will be dissolved into the crystal grains.The average microhardness of the coating increases with the increase of Si content,and CoCrFeNiSi_(2.0)can reach 566.5HV0.5.In 3.5%NaCl solution,the corrosion potential of the coating increases with the increase of Si content,the corrosion potential of CoCrFeNiSi_(2.0)is positively shifted by about 160 mV compared with CoCrFeNiSi0.0,and the corrosion current density decreases from 1.17×10^(-6)A/cm^(2)to 6.06×10^(-7)A/cm^(2),the corrosion resistance is improved.When the Si content is low,continuous large-area corrosion marks appear on the coating surface.As the Si content increases,the surface corrosion is dominated by pitting corrosion.As a result,the addition of Si element to the CoCrFeNi series high-entropy alloy coating can promote the formation of bcc phase,increase the microhardness of the coating,and can effectively inhibit the corrosion tendency of the alloy coating and slow down the corrosion rate of the alloy coating,thereby improving the corrosion resistance.