A Study Of Crystallization Behavior Of Amorphous Containing Coatings

The effect of alloy components on the Fe-(Cr,Ni)-(C,B) amorphous alloy's glass forming capability during arc spraying process was invistigated based on the design amorphous alloy system and parameters optimization of coating process. The Fe-based amorphous alloy coatings with different content of amorphous phase were prepared by arc spraying using the optimized process parameters. The relationship between amorphous content and microstructure of the coatings was established, the tribology and abrasive wear behavior of the amorphous alloy coatings were studied in detail. Furthermore, the microstructures evolution and the wear performance of the amorphous alloy coatings during annealed at different temperatures was discussed. The major results are summarized as follows:The amorphous coatings were prepared by arc spraying technology, the highest amorphous content attainable 65.3%. The optimization arc spraying parameters are: current: 180A; voltage: 32V; air pressure: 0.55MPa; distance: 100mm. Fe-based coatings with different amorphous content were prepared by arc spraying technology under the optimization processing parameters, The coating consists of numerous flattened lamellae parallel to the substrate. The porosity is measured by the image analysis software and the value is between 1.80-2.75% scopes.The microhardness value of the amorphous coatings is more than 1100 HV0.1, and the highest bonding strength reached 69MPa. The coatings abrasive wear resistance are more than 15 times higher than that of the Q235 mild steel, the main wear mechanism were the lamellae brittle fracture and the hard phases brittle spalling. All the coatings were maintain low friction coefficient in the frictional wear process, and the friction coefficient reduced with the increasing amorphous phase content. The mass loss of the coatings were 5.2%-10% of the Q235 steel after 3900 m friction wear test, the main wear mechanism were the lamellae fatigue fracture. The abrasive wear resistance and the ring-on-block wear resistance of the coatings improved with the amorphous content increasing in the coatings. The amorphous phase of the coatings merely occurred structural relaxation when annealed at 400℃and 500℃. The amorphous phase will complete crystallization after heat treatment at 600℃and the predominant crystalline phases precipitated were Fe rich phase and Fe23(C,B)6 hard phase. The crystal grains will gradual growth while the coating heat treated at temperature between 700-900℃, the grains size while remain at the nanocrystalline range. The coating's particle interface will fusing, microstructure compacting and porosity decreasing in the heat treatment process. The microhardness increasing and wear resistance decreasing when the heat treatment temperature increased before the amorphous phase complete crystallization; and then the coating's microhardness decreasing and the wear resistence keep stable.