Study On The Stellite6 Coatings Of Steam Turbine Blades:Residual Stress Control,Microstructures And Properties

Turbine blade is indispensable equipment in the electric power industry.The work environment of Turbine blade is very harsh,moreover the security and service life of turbine blade are seriously restricted by high temperature and high pressure steam,water erosion and fatigue.To water erosion caused failure,advanced surface engineering technology is often used to improve the blade wear resistance,corrosion resistance and ensures the service safety.The coating of plasma cladding and laser cladding has excellent wear resistance and corrosion resistance,and it often used to the repair of the blade.However,due to rapid cooling rate in the solidification of cladding process,the larger residual stress would be induced in the process of cladding.Therefore,the control on the residual stresses of remanufatured coatings has far-reaching significance to improve the service performance and reliability of blade.In this study,nanoindentation test was performed to analyze the influence of three different controlling methods on the residual stress.The microstructure,hardness,wear resistance,corrosion resistance of cladding were investigated.Firstly,the magnetic field is adopted to decrease residual stress.It concluded that the residual stress of the cladding coatings prepared in the transverse magnetic field is smaller than that of the vertical magnetic field and the cladding coatings without magnetic field.The cladding layer prepared in transverse magnetic shows more excellent wear and corrosion resistance.Compared with traditional X-ray diffraction method,Suresh model is more accurate than lee model.By adding rare earth oxide of Y2O3 and La2O3 which changed the elements of the cladding layer,it is concluded that the optimized addition of Y2O3 is 0.5%,La2O3 is 0.8%.And the cladding coating with the optimized addition of rare earth oxide has good resistance of corrosion and wear resisitnce.Ansys was employed to simulate the laser cladding process with the introduction of 316 stainless nets,and the temperature field and stress field were investigated.It proves that the residual stress of the cladding coatings which added stainless steel net is lower.Based on the calculative results of residual stress,the corresponding test of nanoindentation technology also shows that the residual stress of cladding coating with stainless net is lower,but the properties of hardness,wear resistance,and corrosion resistance are reduced.