激光熔覆CoCrFeMnNiMo_(x)高熵合金的组织和耐蚀性研究

Study on the Microstructure and Corrosion Resistance of Laser Cladding CoCrFeMnNiMox High-entropy Alloy

目的为了增强钢制结构表面的耐蚀性,研究Mo含量对CoCrFeMnNiMo_(x)高熵合金组织与耐蚀性的影响。方法采用激光熔覆的方式在N80钢上制备CoCrFeMnNiMox(x=0.1、0.2、0.3、0.4、0.5)高熵合金熔覆层,研究Mo含量变化对高熵合金组织、物相与耐蚀性的影响。结果CoCrFeMnNiMox熔覆试样均由单一的FCC固溶体相组成,随着Mo含量的增加,晶格畸变增大;当Mo的摩尔比超过0.3后,晶粒有长大倾向;Mo的摩尔比为0.5时,表面择优生长晶面由(111)密排晶面转变为(200)非密排晶面。熔覆试样在氯化钠溶液和稀硫酸溶液中的耐蚀性相较N80钢提升明显,其中,CoCrMnFeNiMo_(0.3)的耐蚀性最好,在质量分数为3.5%的氯化钠溶液中其自腐蚀电流密度是N80钢的5%,自腐蚀电位比N80钢提高了1倍;在0.5 mol/L硫酸溶液中,其自腐蚀电流密度是N80钢的31%,钝化区电流密度比N80钢降低了1个数量级。结论在该高熵合金体系中,随着Mo含量的增加,晶格畸变增大。CoCrMnFeNiMo_(x)高熵合金熔覆层可以有效地阻止基体腐蚀的发生。Mo元素在溶液中能够形成MoO_(3)附着在金属表面,从而形成稳定致密的保护层,减少点蚀的发生。CoCrMnFeNiMo_(0.3)熔覆层的耐蚀性最好。

The work aims to enhance the corrosion resistance of the surface of steel structures,the effect of Mo content on the microstructure and corrosion resistance of CoCrFeMnNiMo_(x) high-entropy alloy(HEA)is studied.The CoCrFeMnNiMo_(x)(x=0.1,0.2,0.3,0.4,0.5)HEA coatings were prepared on N80 steel by laser cladding,and the effect of Mo content on microstructure,phase and corrosion resistance of high-entropy alloy was investigated.The results show that the CoCrFeMnNiMo_(x) coating is a typical single FCC solid-solution phase.When the molar ratio of Mo exceeds 0.3,the grain has a tendency to grow.When the molar ratio of Mo is 0.5,the surface preferential growth crystal plane changes from(111)close-packed plane to(200)non-close-packed plane.The HEA coatings can effectively prevent the occurrence of substrate corrosion.Compared with N80 steel,the corrosion resistance of the coating in sodium chloride solution and dilute sulfuric acid solution is obviously improved.The CoCrMnFeNiMo_(0.3) coating has the best corrosion resistance.The corrosion current density is 5%of N80 steel,and the corrosion potential is twice that of N80 steel in 3.5wt.%sodium chloride solution.In 0.5 mol/L H2SO4 solution,the corrosion current density is 31%of N80 steel,and the current density in the passive region is one order of magnitude lower than N80 steel.In CoCrMnFeNiMo_(x) high-entropy alloy system,lattice distortion increases with the increase of Mo content.CoCrMnFeNiMo_(x) high-entropy alloy coating can effectively prevent matrix corrosion.Mo element in solution can form MoO_(3) to attach to the metal surface,forming a stable and dense protective layer to reduce the occurrence of pitting corrosion.CoCrMnFeNiMo_(0.3) coating has the best corrosion resistance.