Research On Microstructure And Properties Of Multicomponent Composite Co-based Coatings Produced By Cladding

High-energy beam surface treatment technology can significantly improve the service performance and service life of mechanical parts,which has been widely used in industrial production and manufacturing field.The research is based on the surface protection of large compressor rotor bearing and blade as the background.So Co-based self-fluxing alloys are extensively used as cladding materials due to their high intensity,good oxidation resistance,corrosion resistance and so on.And new modified materials with comprehensive properties,alloy element Nb,rare earth oxide CeO2,YSZ fiber was added to the cladding coatings.Multicomponent Co-based coatings were prepared on FV520B substrate by plasma cladding and laser cladding.Further,the phase composition,microstructure,element distribution were analyzed.Through hardness test,tensile test,bending test,impact test,friction and wear test at high temperature test,the mechanical properties and high temperature properties of the composite coatings were investigated.The corrosion resistance of coatings was tested by electrochemical experiments.Results indicated that the optimal parameters to produce Co-based,Nb and CeO2 modified composite coatings by plasma cladding technology is current 100A,voltage 30V,speed 4 mm/s,powder feeding rate 30 g/min,ion gas,Ar,801/h,protection gas,Ar,40 ml/min.YSZ fiber modified Co-based coating was successfully prepared by laser cladding technology under the condition of laser power 1000W,scanning speed of 30 mm/s,spot diameter 4 mm.The microstructure of Co-based plasma cladding coating is mianly composed of fine columnar crystal,dendritic and carbide eutectic around.The main phases are ?-Co,Cr23C6.With the niobium addition,NbC forms in the Co-based coatings.Also,finer grain size and equiaxed dendrites are obtained by adding Nb and CeO2.And due to the purification process,few impurities exist in the Nb and CeO2 modified coatings.The introduction of Nb and CeO2 reinforcements shows a positive effect on mechanical properties of micro-hardness,tensile,bending etc,due to the reinforcement mechanism of grain refinement,hard-phase strengthening and purification.A relatively high temperature wear resistance occurs with Nb and CeO2 modification,due to the distribution of high hardness carbide NbC in the cladding coatings as well as the dense and uniform microstructure.In 3.5%NaCl solution,the addition of Nb element enhances the corrosion resistance of the materials,but the addition of CeO2 makes it produce grain boundary reaction easily,so decreased the corrosion resistance.YSZ fibers which change into fine granular dispersed uniformly in the coating.YSZ fibers make micro-hardness and wear resistance of Co-based coating enhanced.Due to the dispersion strengthening of fine granular high hardness,also,Zirconia ceramic and the fine granular YSZ materials with the effect of preventing materials' deformation.