Mo层对锆合金表面微熔NiCr涂层的抗高温氧化机理的影响  

Effects of Mo Layer on the High-Temperature Oxidation Resistance Mechanism of Micro-Melted NiCr Coating on Zirconium Alloys Surface

作　　者：刘耿明 宋国庆 薛康辉 陈勇[1] LIU Gengming;SONG Guoqing;XUE Kanghui;CHEN Yong(School of Mechanical Engineering,University of South China,Hengyang 421001,China)

机构地区：[1]南华大学机械工程学院,湖南衡阳421001

出　　处：《材料保护》2024年第10期11-18,共8页Materials Protection

摘　　要：为提高Zr合金包壳表面涂层的抗高温氧化性,采用多弧离子镀加激光微熔(LMM)的复合技术在Zr合金包壳表面制备Mo/NiCr涂层,通过观察氧化前后的涂层SEM形貌和元素分布,以及通过XRD判断涂层成分,分析涂层抗高温氧化性能的变化。结果表明:经过激光微熔处理的涂层表面孔隙减少,Mo/NiCr涂层激光微熔的功率高于NiCr涂层激光微熔的功率,涂层表面出现非平衡凝固组织特征,随着Mo涂层的添加,在更高激光功率微熔后Zr合金的扩散位置从距涂层表面4.0μm增加到18.5μm。样品在1000℃空气和水蒸气条件下分别氧化30 min后,Zr合金向Mo/NiCr涂层的扩散程度远低于向NiCr涂层的扩散程度,因为有Mo层作为阻挡扩散层阻挡了NiCr与Zr的相互扩散,所以O难以通过Mo层与Zr反应生成Zr_(2)O,并促使β-Zr向着脆性的α-Zr相转变。在涂层中,Zr_(2)O会成为O的扩散通道,而脆性的α-Zr相区域更容易生成Zr_(2)O导致扩散通道增多,极大减弱了涂层的抗氧化作用,最终导致4组检测涂层中,水蒸气氧化的LMM-NiCr涂层中O的扩散程度最深,距离涂层表面足有14.0μm,而水蒸气氧化的LMM-Mo/NiCr涂层O的扩散程度最浅,距离涂层表面仅至1.5μm。这表明Mo的添加可以提高激光微熔的功率,在激光微熔中阻挡Zr向涂层表面的扩散,在氧化中阻挡O向Zr扩散和Zr向涂层表面的扩散,间接阻止O的扩散通道出现和抑制H_(2)O的扩散孔隙生成,Mo的添加提高了涂层的抗高温氧化性能。In order to enhance the high-temperature oxidation resistance of Zr alloy cladding surface coatings,a composite technique combining multi-arc ion plating and laser melting(LMM)was employed to fabricate Mo/NiCr coatings on the surface of Zr alloy cladding.The SEM mor-phology and elemental distribution of the coatings before and after oxidation were examined.Additionally,the composition of the coatings was determined to evaluate the changes in their high-temperature oxidation resistance.Results showed that the surface porosity of the coatings was reduced following the LMM treatment.The LMM power for the Mo/NiCr coating was greater than that for the NiCr coating,and the surface of the coating exhibited characteristics of nonequilibrium solidification microstructures.With the addition of the Mo coating,the diffusion distance of the Zr alloy after LMM at higher power increased from 4.0μm to 18.5μm from the coating surface.After the samples were oxidized for 30 min under conditions of 1000℃in air and water vapor,the extent of diffusion of the Zr alloy towards the Mo/NiCr coating was significantly lower than that towards the NiCr coating.This was attributed to the presence of the Mo layer,which acted as a diffusion barrier,inhibiting the interdiffusion between NiCr and Zr.Consequently,oxygen had difficulty reacting with Zr through the Mo layer to form Zr2O,thereby preventing the transformation ofβ-Zr into the brittleα-Zr phase.In the coating,Zr2O served as a diffusion pathway for O,while the brittleα-Zr phase regions were more prone to the formation of Zr2O,leading to an increased number of diffusion channels and significantly weakening the oxida-tion resistance of the coating.Consequently,among the four tested coatings,the LMM-NiCr coating subjected to steam oxidation exhibited the deepest diffusion of O,reaching a distance of 14.0μm from the coating surface,whereas the LMM-Mo/NiCr coating under the same conditions showed the shallowest diffusion of O,extending only to 1.5μm from the coating surface.This indic

关 键 词：多弧离子镀 Mo/NiCr涂层 激光微熔 高温氧化 

分 类 号：TG174[金属学及工艺—金属表面处理]