Microstructure and mechanical properties of a novel nickel-based powder superalloy

Abstract

A novel nickel-based powder metallurgy superalloy FGH4113A (WZ-A3) was used to manufacture the full-size turbine disks by the process route of “vacuum induction melting + argon atomization + hot isostatic pressing + hot extrusion + isothermal forging”. The microstructure and mechanical properties of the forged FGH4113A alloys under the different heat treatment conditions were systematically studied. The results show that, the full-size turbine disks prepared by FGH4113A alloy have the good macro morphology and homogeneous grain structure. After the subsolvus heat treatment, the average grain size is ASTM 11~13, the yield strength at room temperature and 550 ℃ are 1249 and 1185 MPa, the tensile strength are 1674 and 1656 MPa, and the elongation after fracture are 23.5% and 19.5%, respectively. The mean fatigue life under the conditions of temperature 700 ℃, strain range 0~0.8% and loading frequency 0.33 Hz is 35000 cycles. After the supersolvus heat treatment, the average grain size is ASTM 6~8, the yield strength at 700 ℃ and 800 ℃ are 1063 and 966 MPa, the tensile strength are 1403 and 1112 MPa, and the elongation after fracture are 17.5% and 12.0%, respectively. The mean creep life under the conditions of temperature 800 ℃, stress 330 MPa and creep elongation 0.2% is 384 h. The crack propagation rate under the conditions of temperature 700 ℃ and stress intensity factor range 30 MPa·m0.5 is less than 5×10−4 mm·cycle−1.

Keywords

• nickel-based powder superalloys
• subsolvus heat treatment
• supersolvus heat treatment
• microstructure
• mechanical properties