Effect of Ultrasonic Vibration and Heat Treatment on Microstructure and Mechanical Properties of IN718 Superalloy by Laser Direct Forming

The effects of ultrasonic vibration and heat treatment on the microstructure and tensile properties of IN718 superalloy by laser direct forming (LDF) were investigated. The results show that microstructure of IN718 superalloy with ultrasonic vibration is refined compared with that of the as-deposited alloy. In addition, the microhardness and tensile properties of the parts fabricated by LDF with ultrasonic vibration are improved compared with that of the ones fabricated by LDF without ultrasonic vibration, and the tensile strength, yield strength and area reduction are increased by 2.7%, 6.1% and 10.6%, respectively. With the heat treatment of homogenization, solution and double aging, the columnar dendrites change to equiaxed grains due to recrystallization. Laves phase dissolves, and there are grainy and acicular δ phase distributed in and along boundaries of the grains. Besides, a large number of strengthening phase γ″ and γ' are precipitated on the matrixes. After heat treatment, the tensile strength, yield strength and elongation are 1418 MPa, 1217 MPa and 19%, respectively, which conform to the wrought standard of Q/3B 548-1996. © 2018, Science Press. All right reserved.