Effects of heat treatment on microstructure and high-temperature tensile properties of nickel-based single-crystal superalloys

Abstract

The effects of different heat treatments on the microstructure and the high-temperature tensile properties of a Ni-based single-crystal superalloy were investigated. Experimental results indicated that the Ni-based single-crystal superalloy had severe solidification segregation in the as-cast state, and a large amount of eutectic existed in the inter-dendritic region. To determine the heat-treatment window, the method of homogenization pretreatment was employed. The optimum solution heat treatment was 1280 °C/2 h + 1315 °C/2 h + 1320 °C/2 h + 1325 °C/6 h, AC, and the optimum aging treatment was 1120 °C/4 h, AC + 900 °C/24 h, AC. The shape, size, and distribution of γ′ precipitate had significant effects on the high-temperature tensile properties of the single-crystal alloy. After the optimum heat treatment, the high-temperature tensile strength of the Ni-based single-crystal superalloy was 720.8 MPa, and the elongation was 18.2% at 1000 °C.