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Research On Ceramic Reinforced Ti-Ni Intermetallic Compound Based Composite Coating Prepared By Laser Cladding In-Situ Synthesized On Titanium Alloy

Posted on:2016-12-05Degree:MasterType:Thesis
Country:ChinaCandidate:M J LiFull Text:PDF
GTID:2371330482467873Subject:Mechanical engineering
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Laser cladding in-situ synthesis is a new surface modification technology to improve the surface properties of the substrate.The high density energy of laser beam is used to irradiate the cladding material,which is preset on the surface of substrate,the cladding material and substrate surface were melted,and the element of cladding material reacting with the element of the substrate.the coating and the substrate was metallurgical bonded.In order to improve the hardness and wear resistance of TC4 titanium alloy,laser cladding in situ synthesis technology is used in this paper.High purity B4C,Ti and Ni powders were pre-coated on the surface of TC4,in-situ producing Ti-C,TiB2,TiB ceramic reinforcement phases and TiNi?TiNi2 intermetallic toughness phases.The optimum parameters of laser cladding process were selected by comparing the quality of cladding layer under different technological parameters.The microstructure and phase composition of the coating were analyzed by means of scanning electron microscope SEM,X ray diffraction XRD and energy spectrometer EDS,and the microhardness,wear resistance and corrosion resistance of the coating was tested by HMV-2TADWXY type automatic micro vivtorinox hardness tester,HT-600 type high temperature friction and wear testing machine and CHI660type electrochemical workstation.Experimental results show that the process parameters of laser cladding in situ synthesis directly affect the quality of laser cladding coating.Laser power P=1600-1800W,spot size is 4mm,the preset thickness h=1mm,scanning speed V=4-8mm/s are the best laser cladding process parameters,Under the laser cladding process optimum parameters,it obtained the coating which is the organization continuous uniform,crack free and TC4 titanium alloy matrix are metallurgically bonded with the coating.Laser cladding coating consists of three distinct regions of composition,from the outside to the inside in turn:cladding layer,the bonding zone and heat affected zone.The microstructure composition analysis shows that there is a reaction between C,B,Ni and Ti,in-situ producing TiC,TiB2,TiB ceramic reinforcement phases and Ti-Ni intermetallic toughness phases.The in-situ produced TiC,TiB2,TiB shows the morphologies of fine dendrite,Ti-Ni intermetallic compounds exist in the network structure.The average microhardness of laser cladding layer is remarkably improved.The microhardness of the coat-ing is 680HV0.3-892HV0.3,which is 2-4 times that of the TC4 substrate(290HV0.3-330HV0.3)The wear resistance the coating is 1.7 times that of the TC4 substrate,the corrosion resistanc e the coating is 3 times that of the TC4 substrate,and the main wear form of the coating is abrasive wear.The main wear form of the substrate is abrasive wear and adhesive wear.
Keywords/Search Tags:titanium alloys, laser cladding, in-situ formation, TiC/TiB2/TiB, Ti-Ni intermetallic compounds
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