Effects of Rare Earth Modified Cr Coating on Structure and Oxidation Resistance of Open-cell Ni-Cr-Fe Alloy Foam

In order to further improve the oxidation resistance of the open-cell Ni-Cr-Fe alloy foam, a Y-Cr coatings and a Ce-Cr coating were deposited onto the Ni-Cr-Fe alloy foam by a pack cementation process. The oxidation resistance of Y-Cr and Ce-Cr coatings was also studied under static oxidation conditions at 900 and 1000 degrees C for 120 h. 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). The results show that the Ce-Cr coating is continuous and compact. The surface grain refinement in Ce-Cr coating can be achieved. The interface between the coating and the substrate is combined closely. In addition, the Ce-Cr coated alloy foam has better high-temperature oxidation resistance than the Y-Cr coated foams, and the oxidation kinetics curve of Ce-Cr coated alloy foam follows a parabolic law. It is because a uniform and dense Cr2O3 layer is formed on the surface of the Ce-Cr coating. At the same time, an 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 the substrate.