Research On Microstructure And Properties Of Ni60A Alloy Laser Cladded Coatings Reinforced By Nano-SiC

Nickel-based composite material has good high temperature strength,thermal fatigue,oxidation and hot corrosion resistance,and it can be used in the manufacture of important parts of aviation,ships,and industrial gas turbine engines,which is replacing traditional nickel-based superalloy.The main goal of this topic is to achieve the formation of cladding coating without obvious defects in the process of nanometer SiC particles reinforced nickel-based alloy cladding forming good metallurgical combination.In the process of further research,the influence of Nanoparticles additives on the properties of cladding organization was studied,the ultimate goal is to achieve the formation of nano-composite coating with excellent microhardness,tissue morphology,mechanical strength,corrosion resistance and friction resistance under the condition of the laser cladding.In this paper,the appearance of the topography,including the height,the depth of molten pool and dilution rate was studied by changing laser power P,scanning speed V,defocus distance,spread powder deposition layer thickness,thus the optimum experimental parameters of laser deposition have been defined.On this basis,the phase composition and mechanical properties were changed by adding different proportions of nanometer SiC particles to the deposition layer.The microstructure of the deposited layer,element distribution and phase composition were studied by using metallographic microscope,scanning electron microscope(SEM),energy spectrum analyzer(EDS),X-ray diffraction(XRD).Mechanical properties such as high temperature oxidation and friction and wear were also studied by using microhardness tester,muffle furnace,and friction and wear tester.The experimental results show that,in the current experimental conditions,laser power 400w,scanning speed 8 mm/s,defocus distance 13 mm,thickness of powder 0.8 mm were the optimum experimental parameters for laser cladding.At the top of the deposited layer there are turning dendrites,relatively bulky columnar dendrites for the central and plane and cellular crystal for the bottom of the layer.The density of the dendrites increases gradually with the increase of adding amount of nanometer SiC.XRD analysis results show that there is no SiC phase exist in the organization of the deposition layer,which proves that nanometer SiC particles were decomposited in the process of laser deposition.And the resulting particles formed a variety of gamma interdendritic carbide(M7C3,M23C6).Therefore,the adding of nanometer SiC significantly improves the microhardness of deposition layer.The tester results show that the microhardness of base material and deposition layer without adding nanometer SiC are 350 HV and 590HV,respectively.The microhardness of deposition layer with adding nanometer SiC increases to 1189 HV,3 times of base material 2 times of the latter.Oxidation weight experiments show that in the early stage of the high temperature oxidation,the weight gain of specimen over time into a linear rise.when the oxidation film become complete and compact,the weight gain rate slowed.The experimental results show that when the adding amount of nano SiC was 5%,the oxidation resistance would be best.The adding of Nanometer SiC significantly enhance the wear resistance of deposited layer,the wear mechanism is mainly abrasive wear.With the increasing of adding amount,brittle deformation and cracks would be appeared on the surface of grinding crack.its wear resistance would be best when the adding amount of nano SiC was 5%.