Research On Preparation And Properties Of Intermetallic Compound Coating

Fe-Al intermetallic compound coating was prepared by Flame Spraying-Induction Remelting on 45 steel substrate in this research. A series of research was carried on the coating's preparation technology, subsequent annealing technology, microstructure, mechanical properties and tribological properties. Concrete steps are as following:Powders mixture was obtained by manual mixing, and then Fe-Al intermetallic compound coating was prepared by Flame Spraying-Induction Remelting combined process on 45 steel substrate.Annealing post-processing of Fe-Al intermetallic compound coating was designed by orthogonal method. Microhardness and weight wear rate were set as indexes. Temperature and time were set as influencing factors. The coatings'mechanical properties-microhardness and tribological properties-weight wear rate were tested. Analysis shows that: as for microhardness, the optimized annealing technology is: annealing temperature is 750℃, holding time is 1.5h; as for weight wear rate, the optimized annealing technology is: annealing temperature is 750℃, holding time is 1.5h. So that the optimized annealing technology for the Fe-Al intermetallic compound coating is: annealing temperature is 750℃, holding time is 1.5h. According to the analysis of the abrasive dust and the surface morphology after wear concluded the wear mechanism of the coating is that: at the beginning of friction and wear, the mechanism is adhesive wear; as the friction and wear processing is going on, the mechanism transformed into abrasive particle wear.The components of Fe-Al intermetallic compound coating were analyzed by X-ray Diffraction. The results show that the main phases in Fe-Al intermetallic compound coating are Fe-Al intermetallic compound (including FeAl,Fe₃Al andα-Fe) and carbide precipitation. There are a spot of oxidations of Al and Fe, namely Al₂O₃ and Fe₂O₃, in the coating. Then the tissue of Fe-Al intermetallic compound coating was observed by Metallographic Microscope and Scanning Electron Microscope. Microstructure observation shows that: the coating's microstructure is more uniform after annealing, metallurgical bonding is presented between coating and substrate. The microstructure of Fe-Al intermetallic compound coating can be divided into solid solution regions,strip shape and massive precipitation regions,oxidation regions,pore regions by studying secondary electron images and backscattered electron images.Further research was performed by Transmission Electron Microscope to confirm the phase composition of Fe-Al intermetallic compound coating. The main phases of the coating are intermetallic compound phases such as Fe₃Al,FeAl andα-Fe; carbides as Cr23C6 phase; oxides as Al₂O₃ phase. In addition, dislocations are found in the coating. And dislocation motion phenomenon as dislocation pile-up,cross-slip is observed.Fe-Al intermetallic compound coating was prepared by Flame Spraying-Induction Remelting on 45 steel substrate in this research. It is expected that the intermetallic compound coating will instead Co-based self-fluxing alloy coating,Ni-based self-fluxing alloy coating, to save strategic metal Co,Ni. This paper maybe provide theoretical basis for production application of Fe-Al intermetallic compound coating.