Structure, Strength, and Oxidation Resistance of Ultrahigh-Temperature ZrB2–SiC–WC Ceramics

• Published in: Powder metallurgy and metal ceramics 2021-05, Vol.60 (1-2), p.60-68
• Main Authors: Vedel, D.V., Grigoriev, O.N., Mazur, P.V., Osipov, A.E.
• Format: Article
• Language: English
• Subjects: Boron; Boron oxides; Borosilicate glass; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Depletion; Glass; Grain boundaries; High temperature; Hot pressing; Materials Science; Metallic Materials; Natural Materials; Oxidation; Oxidation resistance; Refractory and Ceramic Materials; Refractory materials; Room temperature; Scale (corrosion); Silicon carbide; Silicon dioxide; Solid solutions; Tungsten carbide; Zirconium; Zirconium compounds; Zirconium dioxide; Zirconium oxides
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-021-00215-3

The hot pressing process was employed to produce dense ultrahigh-temperature ZrB 2 –15 vol.% SiC–5 vol.% WC ceramics. Refractory (Zr, W)C and WB phases emerged in hot pressing at 2050°C and 30 MPa with a holding time of 15 min. The hot pressing process was peculiar in that a (Zr, W)B 2 solid solution formed at the zirconium boride grain boundaries. Annealing in vacuum at 1600°C decreased the amount of oxygen in the ceramics from 0.3 to 0.1 wt.% through interaction of B 2 O 3 , SiO 2 , and ZrO 2 with tungsten carbide. The ZrB 2 –15 vol.% SiC–5 vol.% WC ceramics had 505 ± 60 MPa strength at room temperature and 802 ± 94 MPa strength at 1800°C. The high strength at 1800°C was reached through transcrystalline fracture of zirconium boride grains. High-temperature oxidation resulted in scale consisting of three layers: borosilicate glass as the upper layer, zirconium oxide with other oxide phases (WO 3 and SiO 2 ) as the middle layer, and the base material depleted of boron and silicon as the lower layer. At an oxidation temperature of 1500°C and a holding time of 50 h, the scale was 85 μm thick, including a SiO 2 –B 2 O 3 layer 64 μm thick and a layer of ZrO 2 + SiO 2 + Me x O y and base material depleted of boron and silicon. At an oxidation temperature of 1600°C and a holding time of 2 h, the scale was 84 μm thick, including a SiO 2 –B 2 O 3 layer 10 μm thick and a layer of ZrO 2 + SiO 2 + Me x O y and base material depleted of boron and silicon. The dense scale developed on the material allowed 70% of its initial strength to be retained after oxidation at 1500°C with a holding time of 50 h and 50% strength after oxidation at 1600°C for 2 h, which was higher than for the base ZrB 2 –15 vol.% SiC–5 vol.% ceramics.