Research Of Microstructure And Mechanism Of Composite Modified Coating Using Laser

The aim of this research project was developed laser composite modified coating on metal substrate capable of applying well adhered,full dense coating,high microhardness and good anti-wearing,as well as retains original composition,no dilution,hardly deformation.In order to solve this key problems,using P20 and steel as substrate,the initial position and molten pool shape of laser cladding were analysed and simulated for superior coating firstly,and then cladding process about Nano-SiO2 composite plating and ceramic composite coating were investigated,optimization offset distance from initial position and pool shape,as well as high hardness and anti-wearing comparing with substrate and Nano composite plating were sought after and achieved.However,laser cladding is limited within some applying range due to the dilution,deformation,lower deposition rate,oxidation etc.To maintain constant alloying elements and decrease deformation,many researchers use cold spray process to improve performance of coating.The main advantage of cold spray is that there is no bulk particle melting,hence any materials sprayed retain their initial composition and or phases.Nevertheless in the cold spray process,the material is deposited using a high pressure,high velocity gas jet for the deformation and bonding of particles,the cost is high.It is difficult to deposit brittle or hard materials e.g.ceramics unless they are co-deposited with a ductile matrix aterial.Supersonic Laser Deposition(SLD)combines a cold spray nozzle with a laser to raise and then control the temperature of the impact zone.This softens the substrate and deposited particles,at slower impact speeds,allowing the use of nitrogen gas replace argon.Since SLD offers the potential of combining the advantages of cold spray;solid state deposition,no dilution,low oxidation and high build rates with the ability to deposit a wide range of wear and corrosion resistant materials etc.In this work deposition behavior with Stellite 6 powder impacted on steel under different deposition temperature were numerical analysed,meanwhile,single track and multi-track were sprayed by SLD and investigated coatings structure and properties,laser cladding and thermal spray to allow the structures and properties of the resulting coatings to be compared,acquire a potential technology-SLD,such as,composite deposition on metal substrate capable of applying well adhered,full dense coating,high microhardness and good anti-wearing,as well as retains original composition,no dilution,hardly deformation.