Research On The Heated Microstructure Optimization And High-temperature Properties Of New Single Crystal Nickel-based Superalloy With Low Rhenium

As the key component of the aero engine,the turbine blade has the highest working temperature,the most complex stress and the worst environment,which requires that the material has excellent microstructure and excellent comprehensive performance.Nickel-based single crystal superalloy has been widely used in aero-engine and gas turbine blade because of its unique microstructure and excellent high temperature performance.According to the country's urgent need for nickel-based SC superalloy materials for aero-engine,in this research,taking the newly developed low rhenium nickel based superalloy(DD9-X)for research objects.The effect of heat treatment on the microstructure was studied and optimized.In addition,the microstructure stability and recrystallization behavior of the single crystal alloy were further explored.Ultimately,studied high-temperature tensile and high-temperature creep properties of SC superalloy,analyzed the mechanism of action between single crystal structure and high temperature mechanical properties.The main research results obtained are as follows:The research on optimization of heat treatment process for a new the SC nickel-based superalloy with low-rhenium: The suitable size and distribution of ?' phase was obtained under the condition of 1285?/1 h + 1300?/2 h + 1310?/2 h + 1320?/2 h + 1330?/12 h,the size of ?' phase is about 0.30 ?m,elimination of eutectic phases and reduction of component segregation.There is some difference among the ?' phase morphology under the different heat treatment conditions,from 1000 ? to 1200?,the corresponding ?' phase size grows from 0.35 ?m to 0.57 ?m,the average size of the ?' phase at 1120? is 0.43 ?m.Above the 1160 ? fine second ?' phase in the matrix channel precipitated in the substrate channel,?' phase angle passivation and its morphology to spherical transition.The size of the ?' phase treated at 1160?/1 h + 1120?/4 h is longer than 1120?/4 h,about 0.50 ?m,no second ?' phase phase precipitated.The aging time is increased from 2 h to 8 h at aging temperature of 1120?,the average size of the ?' phase increases from 0.28 ?m to 0.54 ?m.The second ?' phase precipitated in the matrix after 6 h.Cubicity,size and total number of integrals of the ?' phase are effectively adjusted after 870?/24 h.The research on the microstructure stabilities and recrystallization behavior of a new SC nickel-based superalloy with low-rhenium: Long-term exposure test of single-crystal specimens treated at 1120?/4 h,exposed at 1100? and 870? for 0~700 h.The diffusion rate of the refractory element and the coarsening rate of the ?' phase is faster at 1100?.The roughening of the gamma phase and the subsequent rafting took place earlier than 870?,and it would eventually form suihua organization.Single-crystal as-cast microstructure undergoes deformation of the same load,and the different types of recrystallized grains was formed at different temperatures,the results show: after heat treatment at 1100? and 1200? for 4 h,the recrystallization grains with cellular shape formed;at 1300? for 4 h the dendritic recrystallization occurred;at 1330? for 4 h the equiaxed recrystallization occurred,this is mainly related to the dissolution temperature of the alloy ?' phase.The deformation of the specimen surface under different loads Single-crystal as-cast microstructure undergoes deformation of the same load(500~3000 kg)at 1330? for 4 h,with the increasing of loading,the area and depth of recrystallization was increased distinctly.The research on high temperature tensile and high temperature creep of a new SC nickel-based superalloy with low-rhenium: As the defects in the as-cast microstructure directly lead to poor high temperature mechanical properties,tensile strength is 667.3 MPa,elongation is only 8.7%,however after the heat treatment optimization,the high temperature mechanical properties of the alloy has been significantly improved.Tensile test specimens treated at 1160?/1 h + 1120?/4 h and 1120?/4 h,their tensile strength and elongation respectively are 729.5 Mpa,15.7% and 703.7 Mpa,13.6% at high temperature tensile experiments.For creep at 1100?/137 Mpa,the sample first aged at 1160?/1 h + 1120?/4 h which got 0.5 ?m cubic ?' phases obtained the obtained the longest third creep stage due to the most effective impediment to the motions of superlattice dislocations by contact dislocation networks.So,this SC sample owned the highest rupture time compared to the others under this creep environment.Its rupture time was 38.9 h longer than creep specimens treated at 1120?/4 h,extension rate increased by 1.5%.