Insights into the applicability of laser energy density in directly preparing Al₂O₃-based eutectic ceramics by laser additive manufacturing

Laser additive manufacturing (LAM) has become a promising technique to directly fabricate high-performance Al₂O₃-based eutectic ceramics, but the applicability of laser energy density (LED), a comprehensive index commonly used to regulate the LAM process of metallic parts, in preparing brittle ceramic samples with narrower laser processing windows is not clear yet. In this paper, Al₂O₃/GAP/ZrO₂ eutectic ceramics are prepared by LAM to investigate the effects of LED on forming quality and melting dimensions of the as-deposited eutectic samples. The results indicate that the reliability of using LED as a design parameter depends on the way how it is changed. There is a response relationship between the LED and experimental results when individually adjusting laser power P or scanning speed v, but abnormal phenomena are detected when simultaneously changing P and v. It is found that the melting dimensions obtained under higher LED can be unexpectedly smaller. Moreover, there is a significant difference in the melting dimensions despite using the same LED. In addition, 50 layers thin-wall structured Al₂O₃/GAP/ZrO₂ eutectic specimens prepared under a constant LED present significant differences in the forming quality. It is revealed that the contribution of P to LED is much greater than that of v, which is not consistent with the same influence degree reflected in the calculation formula. Thus, there are significant limitations to utilizing LED to regulate the LAM process of brittle ceramics in consideration of the sensitivity of their forming quality to changes in laser parameters.