GH907合金耐蚀涂层研究

【作者】 刘英坤；

【导师】 余志明； 陈和兴；

【作者基本信息】 中南大学 ， 材料学， 2008， 硕士

【摘要】 本文以镍基高温合金GH907为基体，通过低压等离子喷涂和超音速火焰喷涂技术制备了NiCoCrAlY涂层和NiCr涂层，并对样品进行了热处理。着重研究了涂层的显微组织和抗中性盐雾腐蚀性能。并对涂层的抗热震性能和结合强度进行了分析，得到如下结论：1．喷涂态的涂层可以看到典型的片层状结构，呈现出在沉积过程中形成的层状河流花纹。涂层中存在一些孔洞和空隙，其余地方结合紧密。经过热处理后，涂层的缺陷（如空隙）减少了很多，涂层与基体之间的界面变得模糊，说明热处理过程促进了涂层组织的均匀化。2．喷涂态的NiCoCrAlY涂层，主要是由γ-Ni相、β-NiAl相、少量γ’-Ni₃Al和过饱和的α-Cr相组成的，热处理后，涂层中的相组成发生了变化，γ’-Ni₃Al相增多，并且涂层表面有Al₂O₃生成。喷涂态的NiCr涂层是由γ-Ni和Cr_1．12Ni_2．88两个相组成的；热处理后，涂层和基体之间产生了互扩散，涂层是由Cr₃Ni₂和Fe_0．64Ni_0．36组成的。3．从中性盐雾腐蚀实验结果来看，NiCoCrAlY涂层的抗腐蚀性能优于NiCr涂层。热处理后NiCoCrAlY涂层和NiCr涂层的腐蚀等级都有提高，大部分都可以提高3个等级左右．说明经过热处理的涂层抗腐蚀性能都有提高，且仍是NiCoCrAlY涂层的抗腐蚀性能优于NiCr涂层。EDS分析得知NiCoCrAlY涂层的腐蚀产物是Al、Fe、Ni、Co和Cr等的氧化物和氯化物，NiCr涂层的腐蚀产物主要为Ni、Fe、Co等的氧化物。基体材料的腐蚀产物经过EDS分析知其主要是Fe的氧化物，及少量Ni、Co等的氧化物。经过XRD进一步分析，得出基体腐蚀后的产物主要是Fe的各种复杂的氧化物、NiO、NiCl₂、Al₂O₃等各种氧化物和氯化物。4．喷涂态的NiCoCrAlY样品经过10次热震后，大部分样品都可以观察到裂纹的产生，涂层最厚的5#还发生了涂层大面积的剥落。NiCr系的涂层看不到裂纹，涂层表面有黄色纹路形成的沟壑，这是涂层在热震过程中发生了氧化造成的。热处理态的样品经过50次热震后，跟喷涂态相比，涂层的抗热震性能有了大幅度提高，主要表现在热处理后的样品表面基本上观察不到裂纹，即使是把涂层表面放大到较大倍数，涂层表面仍然观察不到裂纹。更多还原

【Abstract】 The paper is based on GH907 supper alloy and LPPS and HVOF sprayed NiCoCrAlY coatings and NiCr coatings. After parperation, the sample is heated for heat treatment. The emphases are the microscopic structure and neuter salt spray testing resistance of the coatings. For the adhesion and the thermal shock resistance, this paper is also analysed. The conclusions are as follows:1.The sprayed coatings can be seen a typical river- as structure, looking like the river-as figure. Someweher in the coatings there are pores, but the other areas combine tightly. After heat treatment, the defects （pores.ext）of the coatings reduce a lot,and the interface between the coating and matrix becomes blurry. This indicates that the heat treatment accelerates the structure of the coating becoming uniform.2. The sprayed NiCoCrAlY coatings is mostly composed byγ-Ni、β-NiAl、a littleγ’ -Ni₃Al and some supersolubilityα-Cr. After heat treatment,,the phases in the coating change.Theγ’ -Ni₃Al is increased, and there are some Al₂O₃ spaned in the surface of the coating. After heat treatment, the phases in the NiCr coating change fromγ-Ni and Cr_1.12Ni_2.88 to Cr₃Ni₂ and Fe_0.64Ni_0.36 because of the diffusetion between the coating and matrix.3. From the results of the neuter salt spray testing, the corrosion resistance of the NiCoCrAlY coating is better than the NiCr coating and it is improved after the heat treatment; also the NiCoCrAlY coating is better than the NiCr coating. Through EDS analyse, the corrosion products of the NiCoCrAlY coating are oxides or chlorides of Al、Fe、Ni、Co and Cr. The corrosion products of the NiCr coating are the oxides of Ni、Fe、Co.ext.The corrosion products of the matrix are oxides of Fe,a little oxides of Ni、Co.ext. After farther analyse of XRD, the corrosion products of the matrix are complicated oxides of Fe,NiO、NiCl₂、Al₂O₃.ext.4.After 10 times of thermal shock, there are many cracks be seen in most of the sprayed NiCoCrAlY coatings, and the thickest 5# coaings can be seen the flaking from the matrix.The NiCt coating can not be seen the cracks, but can be seen many yellow ravines in the coatings,which are the oxide productions. Compared to the sprayed coatings, the thermal shock resistance of the heat treatment coatings improves a lot. No cracks can be seen in the surface of the coatings in big multiple.更多还原