Investigation of the microstructure, high temperature oxidation and deformation behavior of Hastelloy X superalloy fabricated by ultrasonic vibration laser directed energy deposition

In this paper, the effect of ultrasonic vibration on the microstructure and high-temperature properties of Hastelloy X fabricated by laser directed energy deposition (LDED) was investigated. With applying ultrasonic vibration, the superalloy grains were significantly refined from 72.23μm to 44.92μm, and the fiber texture was transformed from <100>//z (building direction, BD) to <111>//z (BD). There was almost no effect on the phase composition of the superalloy. In addition, with applying ultrasonic vibration, the oxidation weight gain of LDED Hastelloy X high temperature oxidation sample was lower, and the oxidation rate constant k value decreased from 0.6416 to 0.5108, which was reduced by 20.38 %. The samples without and with the application of ultrasonic vibration generated a continuous oxide film, which hindered the further occurrence of the oxidation reaction. The thickness of the oxide film decreased from 6.47μm to 4.89μm, a decrease of 24 %. The oxide film was mainly composed of two parts. The surface was composed of Cr ₂O ₃ and spinel oxides FeCr ₂O ₄, NiFe ₂O ₄ and NiCr ₂O ₄, and the part near the substrate was a single Cr ₂O ₃ oxide. With applying ultrasonic vibration, the phase composition of the oxide film surface did not change much, but the proportion of single Cr ₂O ₃ oxide inside was higher, which had better high temperature oxidation resistance. With applying ultrasonic vibration, the peak stress of high temperature deformation of LDED Hastelloy X specimen increased from 364.1 MPa to 410.7 MPa, with an increase of 12 %. The high temperature deformation resistance of LDED Hastelloy X was enhanced with ultrasonic vibration.