Cyclic Ablation Behaviors of ZrB₂–SiC Composites Sintered with Nano‐Sized Particles

Abstract

Ultra-high temperature ceramic (UHTC) is one of the most promising materials used in thermal protection system for hypersonic flight vehicles. In this work, ZrB 2 -0.5 vol% SiC composites are fabricated with nano-sized ZrB 2 and SiC particles by spark plasma sintering (SPS) at 1500 C. The average density of the composites reaches 5.47 g cm À3 , while the average grain size is only 1 μm. Then, single and cyclic ablation tests are conducted using a plasma generator. Ablation mechanisms and microstructure evaluation of the composites are discussed in detail. In addition, a digital optical microscope system is adopted to obtain the surface micrograph after ablation. Results show that ablation center will become protuberant rather than form an ablation crater, due to the relative porous and loose oxide layer and flushing action of ablation flame. Thickness of oxide layer and mass gain of the sample obviously increase during the single ablation, while the mass change rate decreases gradually and is then kept stable with the ablation time increasing. Compared with the single ablation, the cyclic ablation leads to higher mass gain and mass change rate, as many microcracks formed on the surface which will significantly accelerate the oxidation.

Effect of Single Loading Time to the Cyclic Ablation of C/C-SiC-ZrC Composite

“…Some studies confirmed that cyclic ablation rates were lower than those under single loading when the total impacting time of combustion was the same, because the longer single loading time resulted in higher surface temperatures [ 29 , 30 , 31 ]. Other studies [ 32 , 33 ] suggested that shorter single loading times resulted in higher cyclic ablation rates for the strengthened thermal shock. Recently, cyclic ablation of C/C-SiC-ZrC-ZrB 2 under different loading spectra indicated that the ablation rates rose sharply as the single loading time increased from ms to s [ 34 ].…”

Engineered Role of SiC Particle Size on Multi‐Length‐Scale Wear Damage of Spark Plasma Sintered Zirconium Diboride

“…Enormous research has been carried out to study the effect of reinforcements on the mechanical, oxidation, and thermal performance of ZrB 2 . SiC‐reinforced ZrB 2 composites have received special interest, [ 23–25 ] considered as baseline UHTC composites [ 17,26–29 ] with 20 vol% SiC as optimal for aerospace applications; [ 30–33 ] however, studies regarding the effect of reinforcement on tribological behavior are available in scarce as compared with studies on other aspects, such as mechanical, thermal, and oxidation behavior.…”