| The new general Nickel-Cobalt-based superalloy requires both good mechanical properties and process properties.The development of new alloys can be enhanced by adjusting theγ′phase strengthening elements（Al,Ti,Nb,Ta）and increasing the Co content to reduce the alloy low stacking fault energy.The composition adjustment of superalloys will bring a huge space for composition design.Through high-throughput calculation and experiments,the preparation cycle of superalloys with complex composition can be significantly shortened and a large number of experimental data of alloys can be obtained.Selective Laser Melting（SLM）is the most advanced field for superalloys.It is a new process for precision forming of high performance superalloy materials.The combination of high-throughput and additive manufacturing technology can achieve efficient preparation of materials with different compositions,which is of great significance for the development of new materials.In this paper,thermodynamic calculation and high-throughput SLM preparation method are used.The evolution ofγ’andηphases with different Nb and Ta contents in new Ni-Co-based superalloy was researched.Precipitates were systematically characterized by OM,SEM,EPMA and TEM.The relationship between composition,microstructure and mechanical properties of the alloy was established.The main results are summarized as follows:（1）According to the thermodynamic calculation,it is found that the additions of Nb and Ta can reduce the solution temperature ofγ’phase and expand the range ofγphase region.Based on the advantages of high-throughput experiments,the composition gradient samples with Nb content from 1%to 6%and the samples with Ta content from1%to 4%were prepared by SLM method.（2）The volume fraction ofγ′phase in alloys aged at 800°C for 100 h,increases with the increase of Nb content,reaches the highest value of 52%at 3.5%Nb and then decreases.When the Nb content reaches 2.2%,ηphase with DO24 structure starts to precipitate.With the further increase of Nb content,the size and volume fraction ofηphase gradually increase,and the hardness and strength also increase.In order to ensure a suitable volume fraction ofγ′phase and excellent structural stability,it is recommended that the addition of Nb is less than 2.2%.（3）After aging at 800°C for 100 h,γ′phase is uniformly precipitated in the matrix for the alloys with different Ta content,and the average size ofγ′phase is between 70nm and 80 nm.The volume fraction ofγ′phase is the largest for the 1%Ta alloy.With the increase of Ta content to 3%,theηphase begins to precipitate.The hardness and strength increase,and the plasticity decreases slightly with the increase of Ta content.It is suggested that the addition of Ta in the alloy should not exceed 2.0%.（4）It is found that the aging process provides a driving force for the diffusion of alloying elements,and the stacking faults in theγ′phase provide a favorable position for the nucleation ofηphase.The formed atomic steps provide positions for the diffusion of Nb,Ti and Ta,and continue to grow through Ostwald ripening.Noηphase precipitated even if the ratio of Al/（Nb+Ta+Ti）in the 2.0%Nb alloy is lower than 0.85.This may be attributed to formingγ′-Co3Ti phase between the high Co content with Ti in the alloy. |
