Effects Of Trace TiC Nanoparticles On The Microstructure And Properties Of The Cast K4169 Superalloy

K4169 cast superalloy is widely used in aerospace,shipbuilding and other fields because of its excellent mechanical properties and corrosion resistance at room and medium temperature.With the development of science and technology,the traditional superalloy materials can not satisfy the increasing demand of modern science and technology.The conventional casting of K4169 superalloy has many problems,such as coarse grains,coarse intergranular precipitates,uneven distribution of??phase and???phase,which affect the performance of the material.Researches show that grain refinement can effectively improve the strength plasticity,stress rupture and fatigue properties of the alloy,and the addition of refiner is an effective means of grain refinement.Nanoparticles can effectively refine the grain and improve the properties of the alloy.However,how to improve the mechanical properties and corrosion resistance of the alloy at the same time is rarely reported.In addition,there are few studies on nanoparticles as refiners for superalloys.In this paper,TiC nanoparticles were used as refiner,and different contents of TiC nanoparticles were added into Nickel base superalloy K4169 by master alloy method.The alloy was strengthened by standard heat treatment process.The microstructure of as-cast and standard heat-treated samples was compared and analyzed.Finally,the mechanical properties at room temperature and high temperature and corrosion resistance were tested.The main conclusions are as follows:(1)TiC nanoparticles can refine the grain size of nickel base cast superalloy K4169 by about 50%.After adding TiC nanoparticles,the dendrite spacing and the area of interdendritic segregation decrease.The dendrite spacing decreases from 46.2?m to 39.6?m and 38.0?m with 0.02wt%and 0.1wt%TiC nanoparticles,respectively.The area ratio of segregation area between dendrites decreased from 28.1%to 19.4%and 17.4%, respectively.The size and area proportion of Laves phase are reduced.The strengthening phases between dendrite arm and dendrite increase,the strengthening phases with larger size decrease,and the strengthening phases with fine dispersion increase.(2)After standard heat treatment,eutectic Laves phase and bulk strengthening phase dissolve back.With the addition of TiC nanoparticles,the number and size of?phase decrease, and gradually become more uniform from the agglomerated state.The Laves phase wrapped by?phase decreases.The size of precipitates between dendrite arm and dendrite is more uniform,and the size of precipitates between dendrites decreases.(3)After adding TiC nanoparticles,the yield and tensile strength of K4169 superalloy can be significantly improved,but the elongation decreases.The content of 0.1wt.%was the most obvious.The yield and tensile strength of as-cast alloy are increased by 26.3%and 21.0% respectively,and the elongation is decreased by 35.9%.The yield strength and tensile strength of the standard heat-treated alloy are increased by 20.0%and 6.9%respectively, and the elongation is decreased by 48.5%.At the same time,the Rockwell hardness and micro dendrite arm Vickers hardness also increase correspondingly.The high temperature hardness at 600?,650?and 700?was improved with the addition of TiC nanoparticles and the increase is most obvious when the content of TiC nanoparticles is 0.1wt.%.(4)The addition of TiC nanoparticles improves the intergranular corrosion resistance of nickel base superalloy K4169.The results of polarization curves and impedance spectroscopy in 3.5wt.%Na Cl solution and 10vol.%H₂SO₄ solution show that the addition of TiC nanoparticles can reduce the corrosion current density of nickel base superalloy K4169,increase the corrosion potential of the matrix,reduce the dissolution rate of the alloy in the medium solution,and enhance the corrosion resistance of the alloy.