超音速火焰喷涂c-BN/TiC增强NiCrBSi复合涂层的摩擦学性能研究OA

Wear of mechanical components affects production operations and the application of wear resistant coatings to the wear areas is a cost-effective solution,but the lack of wear resistance of alloy coatings is a key challenge limiting their engineering applications.Adding hard phase to improve the wear resistance of coatings is a common reinforcement method,but the addition of a single reinforcement phase and the uneven distribution of reinforcement phases in coatings limit the improvement of the wear resistance of coatings.NiCrBSi coatings are among the most widely used coatings in various industrial applications,protecting materials from wear,corrosion and oxidation.However,compared with the excellent corrosion resistance and oxidation resistance,the wear resistance of NiCrBSi coatings is still insufficient and there is still room for further improvement.TiC is a commonly used ceramic reinforcing phase,which is often used to improve the wear resistance of coatings.Ceramics are characterized by abrasion resistance,high strength and hardness,but poor toughness.The hardness of cubic boron nitride is second only to that of diamond and its bending strength and fracture toughness are between that of cemented carbide and ceramics,making it an ideal coating reinforcement phase.In order to further improve the wear resistance of the coating,the work aims to develop a kind of NiCrBSi composite coating with two ceramic reinforcing phases. The ball milling technique was used to pulverize the particle size of NiCrBSi alloy phase mixture to less than 15 μm,which was mixed with c-BN and TiC/c-BN ceramics,respectively.The mixed powders were also configured to form an aqueous slurry with a uniform distribution of the metal-ceramic phase at a solid content of 40wt.%.The mixed slurry was made into spherical powder by spray granulation technology,followed by sintering in vacuum at 1 000℃for 2 h and then the spherical powder suitable for thermal spraying of 15-65 μm was obtained by sieving.NiCrBSi and c-BN,TiC/c-BN reinforced NiCrBSi composite coatings were prepared on the surface of 304 stainless steel substrate(20 mm×20 mm×5 mm)by high velocity oxygen fuel(HVOF)spraying technique.The microstructure,phase structure and mechanical properties of the composite powders and coatings were evaluated by microhardness tester,scanning electron microscope and X-ray diffractometer,respectively.The abrasion resistance of the coatings was evaluated with a wear tester and the wear traces were analyzed in detail through probe contact profilometry,scanning electron microscope and Raman spectroscopy. Spherical powders suitable for thermal spraying were successfully prepared and the metal phase and ceramic phases were evenly distributed in the powders.Cermet composite coatings with homogeneous physical phases were also successfully prepared.Among them,the NiCrBSi powders and coatings had the same physical phase,which were composed of γ-Ni,CrSi2,Ni3B and Cr2B phases.In NiCrBSi/c-BN and NiCrBSi/TiC/c-BN coatings,the Cr2B phase in the alloy composition of NiCrBSi was transformed to CrB phase.The hardness and wear resistance of the coatings were improved by adding ceramic reinforcing phase.Composite coatings had the same volume content of reinforced phases,while composite coatings containing TiC were harder and more wear-resistant.The TiC/c-BN reinforced NiCrBSi composite coating had the highest hardness of 838.0HV0.3 and also exhibited the best tribological properties with a wear rate of 4.6×10-6 mm3/(N·m). The wear resistance of the composite coatings at room temperature is better than that of NiCrBSi coatings,because the ceramic reinforcement phase improves the plastic deformation resistance of the composite coatings,thus improving the hardness and wear resistance of the coatings.The predominant wear mechanism of NiCrBSi coatings changes from adhesive wear to predominantly particulate wear for composite coatings.The NiCrBSi/TiC/c-BN coatings have the best wear resistance due to the synergistic reinforcement of TiC and c-BN.The synergistic effect of the two ceramic phase slows down crack growth and enhances the plastic deformation resistance of the coating,thus making the coating have the highest hardness and best wear resistance.