等离子喷涂FeCoCrNiMo高熵合金涂层高温氧化行为的研究

Preparation of FeCoCrNiMo High-entropy Alloy Coating and Its Oxidation Behavior

目的基于海工装备与船舶动力装置对高温环境抗氧化涂层的需求,研究FeCoCrNiMo高熵合金(High Entropy Alloy,HEA)涂层制备工艺、微观组织结构与抗高温氧化行为之间的关系,探索其在船舶主机、海洋钻井平台温管等高温部件应用的可行性。方法使用大气等离子喷涂(Atmospheric Plasma Spraying,APS)工艺制备FeCoCrNiMo涂层,设计正交试验来选取不同孔隙率的涂层试样。通过XRD、SEM和EDS分析涂层的物相组成、微观结构和元素组成。对涂层进行氧化试验,分析其氧化行为。结果通过正交试验优化FeCoCrNiMo涂层制备工艺后,涂层孔隙率为2.85%~7.52%。对具有代表性的7.52%孔隙率涂层(记为H1)和2.85%孔隙率涂层(记为H2)进行分析,发现涂层物相结构为简单FCC结构,微观组织为典型的层状结构,氧化物和HEA相在涂层内部分布明显。FeCoCrNiMo涂层的氧化行为遵循抛物线定理,在氧化过程中,化学性质活泼的Cr最易析出并生成氧化物。具有较低孔隙率的H2涂层更快生成致密氧化层,氧化质量增速较低,经15 h氧化后,H1和H2涂层的氧化速率分别约为6.46 mg/cm^(2)和5.16 mg/cm^(2)。结论使用正交试验可以优化FeCoCrNiMo涂层的组织结构,提高涂层的耐氧化性能,使其在海工装备与船舶动力装置中的抗高温氧化应用成为可能。

In order to investigate the relationship between the preparation process of FeCoCrNiMo high entropy alloy(HEA)coatings and the porosity of the coatings,as well as the differences between the microstructure and oxidation behavior of different coatings.We used the atmospheric plasma spraying(APS)process to prepare FeCoCrNiMo coatings and designed orthogonal tests to select coating specimens with different porosities.The microstructure and elemental composition of the coatings were observed by XRD physical phase analysis,SEM and EDS,and the differences in oxidation behavior of the different coatings were analyzed.It was found that the coating porosity was distributed between 2.85%~7.52%after optimization of the FeCoCrNiMo coating preparation process by orthogonal tests.The most representative 7.52%porosity(denoted as H1)and 2.85%porosity(denoted as H2)coatings were analyzed,both of which had a simple FCC structure with a typical lamellar microstructure and a significant distribution of oxide and HEA phases inside the coating.The oxidation behavior of FeCoCrNiMo coating follows the parabolic theorem,during the oxidation process,Cr,which is chemically active,is most likely to precipitate and generate oxides.The metal atoms that are desolvated mainly include Cr and a small portion of Ni that react with O.The element Mo,which has a large atomic diameter,has a low solubility in the HEA alloy phase due to the large difference in atomic size with other elements,and during the high temperature oxidation process,with the desolvation of Cr and Ni elements and the reduction of the lattice size of the two elements,it also precipitates out of the alloy phase and exists as a single mass in the in the coating.The H2 coating with lower porosity generates dense oxide layer faster and has lower oxidation mass growth rate,which is about 5.16 mg/cm^(2) after 15 h.The FeCoCrNiMo coating with lower porosity has better oxidation resistance,and the orthogonal test can be used to optimize the porosity of the coating effectively.