Research On Numerical Simulation About Turbine Blade Microstructure Evolution In Die-forging

Blade is one of core components in turbine, which playing important roles in energy transformation. Due to complicated shape and special alloy, turbine blades usually are difficult to be deformed. Blade die-forging is a complex process affected by multi-factor. There's complicated relationship among deformation, heat transfer and microstructure evolution during blade forging. For the mechanical performance of blade largely depends on microstructure, it has a practical significance to predict and control the microstructure of the blade in planning reasonable technical scheme and improving over-all mechanical properties.Based on numerical simulation technology, in this paper, blade forging process and its microstructure evolution is studied, using constitutive equation reflecting flow stress and Cellular automata reflecting microstructure evolution. At the same time, considering the effects of initial forging temperature; initial energy, initial temperature of dies and friction coefficient on blade quality and microstructure, an orthogonal experiment method was used to seek technical scheme for ensuring the formed quality, ultimate microstructure and mechanical performance of die-forging blade.The study shows:(1) In the process of blade forging, the strain and strain distribution at the blade root are different from the blade body, that the strain of the former is lesser than the later. The distribution of temperature is asymmetric too, and the temperature of blade root is higher than the blade body. When the other process condition are the same, the higher temperature is benefit to metal flowing, which can make billet easy to deformed and reduce hammering times. Good lubricate condition can improve metal flowing property, reduce the friction between billet and dies, decrease the asymmetrical deformation and remnant stress.(2) Making use of Cellular automata, the dynamic recrystallization(DRX) phenomenon in the blade die-forging process can be well opened out including the variation of dislocation density and grain shape, orientation and mean size. The simulated results agree basically with ultimate microstructure of DRX based on classical theory and physical experiment.(3) For the hamming speed is very rapidly, the effect of temperature on nucleating rate and the grain mean-size of DRX is smaller. Strain and strain rate typically influence the microstructure of die-forging blade.(4) Whether on the section of blade root or the section of blade body, gain size at free surface < at contact interface < at center, which is actually lied on strain rate, temperature and friction etc.(5) After completing die-forging and air-cooling treatment, the mean grain size of different section in blade is relate to the temperature value and temperature changing speed of these sections.