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

Abstract

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 Cr2O3 and spinel oxides FeCr2O4, NiFe2O4 and NiCr2O4, and the part near the substrate was a single Cr2O3 oxide. With applying ultrasonic vibration, the phase composition of the oxide film surface did not change much, but the proportion of single Cr2O3 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.