Effect of ultrasonic power on forming quality of nano-sized Al2O3-ZrO2 eutectic ceramic via laser engineered net shaping (LENS)

Abstract

Nano-sized Al2O3-ZrO2 eutectic ceramic structures were formed by ultrasonic-assisted laser engineered net shaping (LENS). The effects of ultrasonic power on shape, internal cracks, pores and periodic banded structure of nano-sized Al2O3-ZrO2 eutectic ceramic were investigated. X-ray diffraction analysis and scanning electron microscopy observation were carried out for sample phase composition and microstructure respectively. The results show that with the increase of ultrasonic power in the range of 60–140W, the mechanical effect and the acoustic streaming effect of ultrasonic increase the area of molten pool and the width of cladding layer. When the ultrasonic power is raised from 60W to 80W, the thickness of the cladding layer has little change. After reaching 80W, with the ultrasonic power increasing, the width of cladding layer increases while the thickness reduces gradually. The number of cracks decreases obviously with the increase of ultrasonic power. When the ultrasonic power is 60–80W, the maximum crack length is kept in the range of 3.5–4.5mm. When the ultrasonic power is 80–140W, with the increase of ultrasonic power the length decreases obviously. The porosity shows the law of decreasing first and then increasing. After the ultrasonic power exceeds 120W, the porosity changes little in the range of 1.15–1.20%. At 100W and 150W, the minimum and maximum porosity 0.45% and 2.55% occur, respectively. The thickness of the periodic banded structure is gradually reduced as the ultrasonic power increases. With the increase of ultrasonic power, the divorced eutectic zone decreases until it disappears, and when the ultrasonic power is 120W, the divorced eutectic zone disappears and the size of the organization coarsening zone is controlled at 2 ± 0.5µm.