Crucible-free fabrication of ZrB2-SiC composite ceramics with ultra-fine eutectic microstructure by laser surface zone-melting: The selection of lasers

Here we report the crucible-free fabrication of ZrB2-SiC composite ceramics by laser surface zone-melting (LSZM, a rapid solidification method) using Nd: YAG laser, ytterbium-doped fiber laser, and CO2 laser, respectively. Based on the comparative investigation of the thickness and the microstructure of the laser processed zone, this work highlights that the CO2 laser is the most suitable laser resource for the fabrication of highly dense and largescale ZrB2-SiC composite ceramics with the eutectic colonies consisting of maze-shaped eutectic microstructure by LSZM. The high temperature gradient up to -4 x 105 K/m using CO2 laser extremely reduces the phase size down to submicron-scale, which contributes to the high relative density (-99%), Vickers hardness (24.18 GPa) and fracture toughness (7.4 MPa m1/2) of the ZrB2-SiC composite ceramics. This work demonstrates for the first time that LSZM is a promising method for the rapid fabrication of dense ZrB2 based ultra-high temperature bulk ceramics.

Automated summary

This study reports on the crucible-free fabrication of ZrB2-SiC composite ceramics using laser surface zone-melting (LSZM) with Nd:YAG laser, ytterbium-doped fiber laser, and CO2 laser. The comparative investigation of the laser processed zone shows that the CO2 laser is the most suitable resource for producing highly dense and largescale ZrB2-SiC composite ceramics with maze-shaped eutectic microstructure by LSZM. The high temperature gradient achieved by CO2 laser leads to submicron-scale phase size, resulting in high relative density, Vickers hardness, and fracture toughness of the ZrB2-SiC composite ceramics.