一种新型第三代镍基粉末高温合金的微观组织及其力学性能

A new third-generation nickel-based powder superalloy WZ-A3 was designed through a thermodynamic software. It was prepared by hot isostatic pressing (HIP) + hot extrusion (HEX) + isothermal forging (IF) + heat treatment (HT) processes. The influence of the process conditions on the microstructure of the alloy was studied. The high temperature tensile, creep and fatigue performances of the alloy after supersolvus heat treatment were also explored. The results show that the average grain size of the HIPed alloy is ASTM 8~9, while coarse γ’ phase exists on the grain boundary and finer γ’ particles present within grain. After extrusion + forging, the grain size reduces to ASTM 13~14, the γ’ particles within the grain are refined, but the number density of large γ’ phase increases significantly. After supersolvus heat treatment, the large γ’ particles at the grain boundaries of the alloy decrease, and the average size of the intragranular γ’ particles is refined from 400 nm in the HIP state to 200 nm in the heat treatment state. Corresponding tensile strength and yield strength of the supersolvus heat-treated alloy at 700 ℃ are 1360 and 1029 MPa, respectively, and the elongation and section shrinkage are 23.5% and 17%, respectively. Under the condition of 800 ℃/330 MPa, the time required for the creep strain to reach 0.2% is 229 h, and the fatigue life at 700 ℃ with a strain of 0%~0.8% is 24 500 cycles. The creep and fatigue performances of the alloy are equivalent to typical third-generation nickel-based powder superalloys such as LSHR and ME3. This self-developed alloy has a tensile strength at 700 ℃ of nearly 50 MPa higher and an elongation of 3 times compared with the supersolvus heat-treated LSHR alloy, but the yield strength is slightly lower.