| As the most structurally complicated hot component which works in the most harsh environment,aerospace turbine blade is one of the core components of the engine.With the development of new aeroengines,service temperature and working load of turbine blade are continuously rising,manufacturing technology of advanced single crystal turbine blade has become the pivotal technology of the aviation industry.Therefore,study of the preparation and optimization for new high-performance turbine blades,and to explore its mechanical properties and failure mechanism has great practical significance.In this paper,a high-performance low-rhenium Nickel-based single crystal superalloy has been researched,the single crystal turbine blades were prepared by high rate solidification(HRS),and the influence of directional solidification parameters on the single crystal forming rate of turbine blades was studied;Furthermore,the effects of heat treatment processes on the micro-structure and mechanical properties of the alloy were discussed;Finally,the room temperature strength and high temperature creep properties of single crystal samples were determined,and the fracture mechanism was analyzed.The results are as follows:The research on solidification characteristics of single crystal turbine blades shows that : For the new superalloy and the selected turbine blade structure,the primary dendritic arm spacing decreases with the increase of the withdraw rate and the increase of the shell temperature,and the stray grains will appear when the withdraw rate is 1mm/min and 4mm/min.The micro-structure of the prepared turbine blades is nonuniform,the primary dendrite arm spacing and the eutectic phase in the thicker place is larger than those in the thinner place.The size of the enhanced phase is much larger at the branching arm than at the branching axis.Thermodynamic simulation and experimental studies shows that:.The proper process not only can eliminate the low melting point eutectic phase,but also cansignificantly improve the as-cast alloy nonuniform structure.The effect of the heat treatment process is that the eutectic phase and coarse ? 'phase structure can not be completely eliminated by solution treatment with low temperature,and slight melt can be caused by the solution treatment with high temperature.The size of ? 'phase precipitated in the alloy increases gradually with the increase of the aging temperature,and the cubic degree increases first and then decreases;Furthermore,overlong solution time and aging time cause ? 'phase corner rounded.The research on the room temperature strength of the alloy shows that:the hardness of the dendritic axis is highest,more than 410 HV,the micro-hardness of the eutectic structure between the dendrites is much lower than that of the dendrites,only about 365 HV.The heat treatment can eliminate the difference of the properties and increase the maximum hardness of the alloys to 450 HV.The tensile strength is more than 1030 MPa.The fracture form of the alloy at room temperature is brittle fracture.The research on high temperature creep property of new nickel-based single crystal alloy shows that:the lifetime of the new superalloy is 450 h,260h,100 h respectively,under the three test conditions at 1100?/100 MPa,1100?/120 MPa,1100?/140 MPa.At given temperature,The first stage of the creep behavior of the alloy is not obvious and the creep quickly enters the second stage.The duration of the second stage is significantly shorter with increasing stress.The The fracture is caused by creep micro-porous aggregation.The rafting micro-structure forms along the vertical direction of the tensile stress axial line in the creep process at 1100?,with the increase in stress,the rafting structure is constantly thickened,and the rafting direction changes at a small angle near the fracture,and the rafting at the fracture is completely broken. |
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