Gas tungsten arc welding of ZrB2–SiC based ultra high temperature ceramic composites

The difficulty in fabricating the large size or complex shape limits the application of ZrB2–SiC composites. Joining them by fusion welding without or with preheating, controlled cooling under protective gas shield leads to thermal shock failure or porosity at the weld interface. In the present work, a filler material of (ZrB2–SiC–B4C–YAG) composite with oxidation resistance and thermal shock resistance was produced in the form of welding wire. Using the filler, gas tungsten arc welding (GTAW) was performed without employing preheating, post controlled cooling and extraneous protective gas shield to join hot pressed ZrB2–SiC (ZS), and pressureless sintered ZrB2–SiC–B4C–YAG (ZSBY) composites to themselves. The fusion welding resulted in cracking and non-uniform joining without any filler material. The weld interfaces of the composites were very clean and coherent. The Vickers micro-hardness across the weld interface was found to increase due to the increase in the volume % of both SiC and B4C in the filler material. The shear strength of the weld was about 50% of the flextural strength of the parent composite.