Powder superalloy has the advantages of fine grain, uniform structure, no macro segregation, high alloying degree, high yield strength and good fatigue performance, and is an excellent material for manufacturing new engine turbine disks with high thrust-to-weight ratio. The first and second generation of powder metallurgy superalloys have been unable to meet the performance requirements of the new generation of aeroengine superalloys. The third generation of powder metallurgy superalloys have high strength and damage tolerance, high temperature resistance and good durability, and the use temperature is 700~750℃.
Throughout the composition design of the third generation powder superalloy at home and abroad, the addition of alloying element tantalum is a remarkable feature. Ta is a strong carbide forming element. Adding tantalum to nickel-based superalloy can improve the stability, crack propagation resistance and thermal corrosion resistance of carbide. Ta has a large atomic radius and its Vegard coefficient is second only to hafnium and zirconium, so it can significantly increase the lattice constant of γ 'phase and improve the solid solution strengthening effect of γ' phase. The Ta added into the alloy mainly enters the γ 'phase, improves the thermal stability of the γ' phase, delays the aggregation and growth of the γ 'phase, and improves the high temperature strength of the alloy. At the same time, Ta can also improve the oxidation resistance and corrosion resistance of the alloy, which is beneficial to improve the high temperature fatigue crack propagation and creep resistance of the alloy. Adding Ta to Cast IN617 alloy can improve its tensile strength at high temperature and microhardness at room temperature. However, when the content of Ta reaches 2.0%, the Ta rich MC carbide in susaturated matrix leads to the decrease of plasticity and fracture toughness. The alloys containing Ta exhibit the Orowan bypass and partial dislocation climbing mechanisms at high temperature. The results show that Ta affects the high temperature tensile deformation mechanism of Co-Al-W-based single crystal superalloys. The deformation mechanism of Ta and 1.8Ta alloys is that the dislocation bypassing the γ 'phase, while the deformation mechanism of 2.8Ta alloys is that the dislocation cutting the γ' phase. The microstructure, tensile properties and deformation behavior of nickel-based powder superalloys with different Ta content were studied in this paper by precipitation hardening nickel-based powder superalloys with γ 'phase size and multi-mode distribution.
At 815℃, the tensile strength of the alloys with different Ta content is increased by 90~130 MPa compared with the alloys without Ta. With the increase of Ta content, the tensile strength shows an increasing trend on the whole, and the yield strength of alloys with different Ta content is higher than that without Ta. Compared with the alloy without Ta, the elongation and section shrinkage of the alloy with Ta content of 2.4% are improved greatly. When the content of Ta increased to 4.8%, the elongation and section shrinkage of the alloy decreased significantly. It shows that the addition of Ta increases the high temperature strength of the alloy obviously, and improves the high temperature plasticity of the alloy with an optimal content of Ta.
