Preparation And Properties Of Reactive Plasma Sprayed TiC-SiC Composite Coatings

In this paper,graphite powders,silicon carbide,and titanium powders were used as raw materials.First,Ti-SiC was compounded by using a protective atmosphere sintering in a vacuum tube furnace.Then,the sintered Ti-SiC powders were mixed with graphite and the agglomerate powders suitable for plasma spraying were prepared.The agglomerate powders were sent into a plasma flame,and TiC-SiC composite coatings were prepared owing to the high temperature of the plasma flame and the self-propagating reaction of Ti,SiC and graphite.The effects of sintered Ti-SiC powders with different molar ratios and sintering temperature on the phase and properties of TiC-SiC composite coatings were systematically studied.The composition and sintering temperature of the powders were optimized.According to the XRD analysis of sntered Ti-SiC powders with different proportions at different temperatures,it could be found that new phases such as Ti C,Ti₅Si₃,and Ti₃SiC₂ were formed.With the same proportion of Ti-SiC powders,the peaks of the Ti C,Ti₅Si₃,and Ti₃SiC₂ phases increased as the sintering temperature increased,with the disappearance of the Ti peak and the decrease of the SiC peak.This suggested that the reaction between Ti and SiC occurred during sintering.The coatings were prepared from the sintered powder,and the microstructure of the composite coating was studied.The composite coating had a typical layered structure with a good bonding interface,a thickness of 200-300?m,and a good density.According to the analysis of the XRD results of the coatings,it was found that the coatings prepared from the sintered powders contained Ti C,Ti₅Si₃,Ti₃SiC₂ phases,and the content of Ti C phases increased with the increase of the sintering temperature.In composite coatings prepared from the sintered powder with the same proportion,the peaks of Ti C,Ti₅Si₃ and Ti₃SiC₂ phases increased with the increase of sintering temperature.Ti C,Ti₅Si₃,Ti₃SiC₂,and SiC phases were present in the coatings prepared from the sintering powders at 1200?.The results of the porosity and mechanical properties of TiC-SiC composite coatings showed that,for the coatings prepared from the sintered powders with the same proportion,their porosity and wear loss decreased as the sintering temperature increased.The microhardness and fracture toughnessincreased.For the coatings prepared from the sintered powders at the same sintering temperature,with the increase of the molar ratio of Ti-SiC composite powder,their porosity and wear loss of first decreased and then increased,and the hardness and fracture toughness first increased and then decreased.Therefore,the molar ratio of sintered powder Ti:SiC=3:1.5,and the coatings prepared from the sintered powders at 1200?had superior performance.The porosity was 6.2%,the average hardness was 1534±133 HV_0.2,and the fracture toughness was 3.6 MPa·m^1/2.Compared with the coating prepared from the powders without sintering treatment,for the coating prepared from the sintered powders,the hardness was increased by 33.1%,and the fracture toughness was increased by 100%.The amount of wear loss was 0.0030 g.By analyzing the wear scar morphology of the coating,it was found that the wear mechanism of the coatings was abrasive-and adhesive-wear.