Effect Of Turbine Blade Casting Process For DZ125 Alloy On Fluorescence Display And Mechanical Properties

Turbine blades are in the terrible environment of high temperature in the aircraft engine so the performance of turbine blades is directly related to the performance index of the whole engine.In this paper,the directional solidification process of DZ125 alloy was adopted and the phenomenon of fluorescence display defects and disqualification of grain orientation was found through preliminary process research.The grain size and fluorescence loose numerical simulation were carried out for the initial defect.The real boundary conditions are obtained by measuring the cooling environment of the directional furnace.Combining the test results with the physical parameters of calculation,the practical scheme is simulated.It is found that the grain size and defects are the same with that of simulation results.Then the loose defect locating inside of edge plate and orientation deviation of the blade body grains have been solved.The causes and formation mechanism of surface fluorescence defect have been investigated by analyzing blade surface and morphology of DZ125 alloy.The results indicates that the surface fluorescence defect of blade is composed of two parts.One is sticky sand rather than inclusions or shell material,which caused by interface reaction between the melt and shell.The defect is closely related to the melt interface mechanism and contact angle ?(wettability).The other is the microporous hole between dendrites which is the result of the microloose and microporosity.The microloose dispersing in dendrite was formed due to the insufficient melt supply.It is related to the temperature gradient of solid-liquid interface during directional solidification.Meanwhile,the displacement reaction of the free Si O2 or ?-Al2O3 with C will produce the micro-porosity.The surface integrity of the blades is destroyed by sticky sand and micro-porosity,which is the main causes of fluorescence defects.It is a key method to reduce the surface fluorescence defects of blades by improving the shell process and the temperature gradient at the front edge of the solid-liquid interface.In order to obtain good microstructure and mechanical properties,the pulling crystal temperatures are 1480?,1510? and 1540?,respectively.Then samples were heat treated according to design technique.The pulling crystal temperature is determined by microstructure observation and mechanical properties measure.DZ125 alloy has been cast according to numerical simulation optimization plan and the temperature for crystal directional growth(1490~1510?).The pass rate is up to 71.5% standing for the domestic top level.And blade performance meets thedesign requirements.