M Shojaie-bahaabad - Assistant Professor, Department of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood, Semnan, Iran
A kargar-Nikjeh - MSc Student, Department of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood, Semnan, Iran

Ultra High Temperature Ceramics (UHTCs) due to unique features that are enough potential for use in aerospace, military and industrial applications In the present work, a ZrC-۲۰ vol% SiC-۱۵ vol% HfB۲ composite was produced by pressureless sintering method. The initial powder was pressed and sintered at ۲۲۰۰˚C for ۲h. The microstructure and mechanical properties of the composite was investigated by Scanning Electron Microscope (SEM) equipped with EDS spectroscopy, XRD analysis and hardness and toughness tests. The ablation resistance of the composite was performed by oxyacetylene torch. During the ablation test, the outer surface of the composite underwent a sintering process and formed a dense layer of Zr-Hf-Si-O on the surface. ZrSiO۴ and HfSiO۴ were also created after cooling, so these phases played a pinning effect and prevented the crack propagation. SEM analysis further revealed that the formed oxide layer on the composite surface was uniform due to the pinning effect of ZrSiO۴ and HfSiO۴ phases.

Composite, Carbides, Ablation properties, ZrC-SiC.