Research On Key Technology Of Diode Laser Cladding Remanufacturing On Steam Turbine Rotor

In order to solve the wear repair problem of large steam turbine rotor shaft journal,laser cladding remanufacturing system was built based on diode laser cladding with coaxial powder feeder.With the material of steam turbine rotor shaft as substrate and the self-made special laser cladding remanufacturing powder as experimental material,the experiments were carried out by laser cladding remanufacturing method.Focusing on effect of laser remanufacturing layer on the key problem of total indicated runout(TIR)of steam turbine rotor,the process experiment research and mechanism simulation verification were performed,and the influence mechanism of different factors were analyzed.The mechanical properties and technical application problems were studied after laser remanufacturing.The outcome of this research provids reference value to solve total indicated runout problems in practical engineering application and subsequent application.(1)Laser remanufacturing special alloy powder materialLaser remanufacturing system includes multiple subsystems,such as special alloy powder material preparation system,laser and robot motion system,powder delivery system and a temperature monitoring system and so on.With the improvement of structure of gas atomization nozzle in special alloy powder material preparation system,the different pressures process experiments were performed on.The test showed that the optimum gas atomization pressure is 7MPa comprehensively and the powders have high spherical degree,better fluidity and larger apparent density,which meet the requirements of laser cladding remanufacturing under the improvement nozzle.(2)Effect of different factors on total indicated runoutLaser remanufacturing process is complex,a great influence of different factors on total indicated runout was found through the experiment.In order to explore influence mechanism,the effects of different factors,such as pore defect of laser remanufacturing layer,different alloy powder material,remanufacturing layer width and laser energy density,on the total indicated runout was studied.A reasonable range of remanufacturing layer width and laser energy density was preliminary proposed:laser remanufacturing layer width L? 9.73mm,laser energy density Pw? 54.55J/mm2?(3)Simulation and verification of different factors by finite element methodThe finite element model of laser remanufacturing layer and substrate was established using ANSYS software.Simulation of pore defect of laser remanufacturing layer,different alloy powder material and remanufacturing layer width on the effect of total indicated runout,analysis of the magnetic lines of force in electromagnetic field,the magnetic flux density and eddy current density of the measured body surface to obtain the impedance of eddy current sensor probe real and imaginary,the factors to influence action mechanism of total indicated runout and the threshold of remanufacturing layer critical width was 9.82mm by simulation calculation.(4)Mechanical properties of laser remanufacturingBased on the previous study of total indicated runout,the tensile,impact,bending mechanical properties,friction and wear properties and resistance cavitation property residual stress test were performed with iron powder F1 after laser remanufacturing by several of analytical measurement equipments.The thesis analyzed the reason of tensile,impact,bending performance improvement and the residual stress problem of laser remanufacturing,put forward the current measures and process methods and provided reference for the application of laser remanufacturing steam turbine rotor.(5)Application of laser remanufacturing turbine rotor shaftApplication of laser remanufacturing steam turbine rotor journal was studied based on process analysis and optimum control.The microstructure,phase structure and microhardness were tested,and the key technical problems of total indicated runout were detected.By comparing the properties of substrate,the superiority of the technology of laser remanufacturing was indicated.By total indicated runout detection,the repair of dissimilar materials on the surface of steam turbine rotor shaft is feasible.