Effect of Si3N4 Addition on Compressive Creep Behavior of Hot‐Pressed ZrB2–SiC Composites. Issue 9 (9th June 2014)

• Record Type: Journal Article
• Authors: Mallik, Manab; Ray, Kalyan Kumar; Mitra, Rahul; Wakai, F.
• Is Part Of: Journal of the American Ceramic Society. Volume 97:Issue 9(2014)
• Page Start: 2957
• Page End: 2964
• Publication Date: 2014-06-09
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.13022
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace13022-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Compressive creep studies have been carried out on hot‐pressed ZrB<sub>2</sub>–SiC (ZS) and ZrB<sub>2</sub>–SiC–Si<sub>3</sub>N<sub>4</sub> (ZSS) composites in air under stress and temperature ranges of 93–140 MPa and 1300°C–1425°C, respectively for time durations of ≈20–40 h. The results of these studies have shown the creep resistance of ZS composite to be greater than that of ZSS. As the temperature is increased from 1300°C to 1425°C, the stress exponent of ZS decreases from 1.7 to 1.1, whereas that of ZSS drops from 1.6 to 0.6. The activation energies for these composites have been found as ≈95 ± 32 kJ/mol at temperatures ≤1350°C, and as ≈470 ± 20 kJ/mol in the range of 1350°C–1425°C. Studies of the postcreep microstructures using scanning and transmission electron microscopy have shown the presence of glassy film with cracks at both ZrB<sub>2</sub> grain boundaries and ZrB<sub>2</sub>–SiC interfaces. These results along with calculated values of activation volumes suggest grain‐boundary sliding as the major damage mechanism, which is controlled by O<sup>2−</sup> diffusion through SiO<sub>2</sub> at ≤1350°C, and by viscoplastic flow of the glassy interfacial film at temperatures ≥1350°C. Studies by transmission electron microscopy have shown formation of crystalline precipitates of Si<sub>2</sub>N<sub>2</sub>O near ZrB<sub>2</sub>–SiC interfaces in ZSS tested at ≥1400°C, which along with stress exponent values <1 suggests that grain‐boundary sliding involving solution‐precipitation‐type mechanism is operative at these temperatures.</p> </abstract>