稀土改性Cr涂层对开孔Ni-Cr-Fe泡沫合金组织结构及高温氧化性能的影响

Effects of rare earth (Y and Ce) modified coating on structure and resistanceto oxidation of open-cell Ni-Cr-Fe alloy foam

摘要:

为了提高三维网状开孔Ni-Cr-Fe泡沫合金的高温氧化性能，本文采用固体粉末包埋工艺在开孔Ni-Cr-Fe泡沫合金表面分别制备Y-Cr和Ce-Cr涂层，再将涂层加热到900℃和1000℃进行120h高温静态氧化试验。利用扫描电镜、X射线衍射仪对两种涂层改性Ni-Cr-Fe泡沫合金的微观组织结构和氧化产物的形貌、成分和相组成进行对比分析。结果表明：Ce-Cr涂层改性开孔Ni-Cr-Fe泡沫合金组织均匀致密、涂层表面晶粒明显细化，且涂层与基体界面结合紧密。同时，Ce-Cr涂层改性泡沫合金的抗高温氧化性能优于Y-Cr涂层，氧化动力学曲线符合抛物线氧化规律。这主要由于其表面生成了均匀致密的Cr2O3氧化膜；涂层与基体之间形成了由Ni-Cr-Fe，[Fe,Ni]相构成的过渡层，使基体与涂层冶金结合，从而加强了涂层与基体的结合力。

Abstract:

In order to further improve the oxidation resistance of the open-cell Ni-Cr-Fe alloy foam, the Y-Cr and Ce-Cr coatings were deposited onto the Ni-Cr-Fe alloy foam by a pack cementation process, respectively. The oxidation resistance of Y-Cr and Ce-Cr coatings were also studied under static oxidation conditions for 120 h at 900℃ and 1000℃. The phase composition, the morphology and microstructure of the Y–Cr coating and the Ce–Cr coating before and after oxidation were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The results show that the Ce–Cr coating is continuous and compact, and surface grain refinement in Ce–Cr coating can be achieved by comparison of experimental results in Y–Cr coating. The interface between coating and substrate is combined closely. Simultaneously, the Ce–Cr coated foam has better high-temperature oxidation resistance than the Y–Cr coated foams, and the oxidation kinetics curve of Ce-Cr coated foam follows a parabolic law. This is because that a uniform and dense Cr2O3 layer is formed on the surface of the Ce–Cr coating. At the same time, interfacial transition layer consisting of Ni-Cr-Fe and [Fe,Ni] is formed around the interface of Ce–Cr coating and substrate to facilitate metallurgical bonding, resulting in enhanced interfacial bonding between the coating and substrate.