Optimization Of Investment Casting Process For Turbine Blade Of K418B

K418B turbine blade is an important part of the engine on the engine,with investment casting method of production.The blade has a large aspect ratio and a wide range of wall thickness variation(1-10 mm),and has a plurality of variable cross sections and bosses.During the casting process,it is easy to produce a shrinkage defect.The casting process is difficult and the product qualification rate is very low.Taking K418B turbine blade of nickel base superalloy as the research object,this paper aims to optimize casting process,improve casting quality and reduce casting defects and shrinkage porosity defects.The influence factors of shrinkage porosity formation are studied by ProCAST numerical simulation and experimental research.But in order to reduce the cost and shorten the trial period,this study is carried out in two stages.Firstly,the thin-walled characteristics of turbine blades were extracted,and thin walled parts of different sizes were designed.The physical parameters and boundary condition parameters of K418B alloy were obtained by simulation.The effects of pouring temperature,preheating temperature of shell and casting speed on shrinkage defects of castings are analyzed.On this basis,the experimental verification was carried out,and a preliminary conclusion of the K418B Thin-walled Casting casting process was obtained.After that,the preliminary conclusions are applied to the technological design of investment casting for turbine blades,and the numerical simulation is optimized by ProCAST software,and the process is verified by casting and casting experiments.By optimizing the technology,the shrinkage defects of the castings have been greatly reduced,and the qualified turbine blade castings have been obtained.The qualified rate of the products is increased from 30%to 55%.The research has made the following main conclusions:(1)Through experimental measurement and Jmatpro software calculation,the thermal physical parameters and mechanical performance parameters of K418B investment casting simulation were obtained,and the material library of ProCAST software was complemented and perfected.The main parameters of the alloy are as follows:the liquidus temperature is 1360?,the solid phase line is 1200?,and the latent heat of solidification is 248.4 J/g.(2)For thin-walled parts with modulus of 0.5?4 mm,pouring temperature,shell preheating temperature and pouring speed are important factors affecting shrinkage and shrinkage defects of thin-walled parts when the structure and size of gating system remain unchanged.When the pouring temperature is within 1400?1500? the shrinkage and shrinkage will decrease with the increase of pouring temperature,but when the temperature is over 1500?,the shrinkage cavity will increase.When the preheating temperature of the shell is changed in the range of 900?1050 ?,the shrinkage cavity of the castings increases with the increase of the shell temperature.When the casting speed varies from 0.4 to 0.8 m/s,the shrinkage porosity of the castings has little effect.The casting temperature can be improved properly in the design of the casting process of thin wall parts,but it should not be higher than 1500?,and the shell temperature can be reduced,but it must not be less than 950?.The optimum pouring process of the thin-walled parts is:the pouring temperature is 1500?,the preheating temperature of the shell is 950 ?,and the pouring speed is 0.6 m/s.The complete casting can be obtained at the time of experiment,which is in agreement with the simulation results.When the casting position of the pouring system is changed,the effect of the side injection is better than the bottom injection.Thin wall casting pouring system with internal sprue can achieve feeding,and ingate should be thinner than the thickness of the casting wall.(3)When the K418B turbine blade is cast,the factors that affect the shrinkage and shrinkage are the preheating temperature of the shell,the pouring temperature and the casting speed.The optimized casting process parameters of turbine blade are:open casting system,the ratio of runner section and inner runner section is 1:1.9,pouring temperature is 1500?,the preheating temperature of shell is 1080?,and pouring speed is 0.6 m/s.In this process,the shrinkage defects are greatly reduced,and the turbine blades with excellent quality are obtained.