Study On Corrosion And Wear Behaviors Of Arc Spraying Fe-based Amorphous Composite Coatings

Fe-based metallic glasses have attracted an increasing attention owing to its unique microstructure, excellent physical, chemical and mechanical properties, and the relatively lower material cost. However, the applications of these amorphous alloys have been blocked due to the high cooling rate, required for amorphous formation, and the small sizes. Producing amorphous and nanocrystalline composite coating on the substrate is a good way to improve the surface properties of the substrate alloy. Amorphous coatings can be obtained by arc spraying technique due to the characteristics of non-equilibrium melting and cooling in the spraying processing. The objective of this study is, therefore, to investigate the feasibility of arc spraying Fe-based amorphous coatings to improve the corrosion resistance and wear resistance properties of the substrate.In this paper, the Fe-based alloy coatings were fabricated on 45# steel by arc spraying. The phase composition, microstructure, micro-area composition distribution, microhardness, corrosion and wear resistance of the coatings were analyzed by X-ray diffraction(XRD), optical microscope(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), microhardness tester, electrochemical measurement system and friction and wear tester. The effects of heat treatment and laser remelting processing on the microstructures and properties of as-sprayed amorphous composites coatings were investigated. The corrosion and wear mechanism of the coatings were also explored.The results show that the arc sprayed coating mainly consist of amorphous and BCC-(Fe,Cr) solid solution, whose lattice parameter is a=2.8615?. The as-sprayed coating is a typical layer-structure, which is deposited by well deformed flat metal particles. Some porosity and oxide inclusions are existed in the coting. The porosity of the coating is about 2.87%. Perfect mechanical bond is obtained between the coating and substrate. The microstructure of the as-sparyed coating can be uniformed and the porosity can be lowered by suitable heat treatment. The porosity of the coating, which is heat treated at 800℃ for 30 min, is about1.92%. There is a metallurgical bond between the layers. The laser remelted coating mainly consist of Fe2 B and(Fe,Cr) solid solution, whose lattice parameter is a=2.8681?. The microstructures and composition of the coating are well-distributed after laser remelting.As-sprayed coatings possess good corrosion resistance. The corrosion potential Ecorr and corrosion current density icorr is-0.52 V and 6.95μA/cm2, respectively. The corrosion model can be represented as R(Q(RO(QR))). Two interfaces, coating/dielectric interface and pore/dielectric interface are existed in this corrosion electrode system. Porosity corrosion will occur with the corrosion time increasing. The corrosion potential Ecorr is-0.34 V and corrosion current density icorr is 5.49μA/cm2 of the coating after heat treatment at 800℃, which has a better corrosion resistance than the as-prayed coating. The corrosion model of the heat treated coating can be represented as R(Q(R(QR))). The corrosion mechanism of the heat treated coating is mainly uniform corrosion. The corrosion potential Ecorr is-0.50 V and corrosion current density icorr is 6.87μA/cm2 of the laser remelted coating. The corrosion model of the laser remelted coating can be represented as R(Q(R(QR))). Two interfaces are also existed in the laser remelted coating, but the capactive arc radius increased significantly, and the corrosion resistance improved.The friction coefficient of the as-sprayed coating is about 0.5 and the wear amount is 17 times than the substrate under the same condition. The wear mechanisms of the as-sprayed coating are spalling wear, adhesive wear and abrasive wear. The friction coefficient is decreased significantly and the wear resistance is improved after the coating is heat treated at 800℃. The wear mechanism of the heat treated coating is mainly abrasive wear. The microhardness of the laser remelted coating is decreased, and the wear mechanisms are abrasive and adhesive wear.