Densification, mechanical, and tribological properties of ZrB2-ZrCx composites produced by reactive hot pressing

Kannan, R and Rangaraj, L (2020) Densification, mechanical, and tribological properties of ZrB2-ZrCx composites produced by reactive hot pressing. Journal of the American Ceramic Society, 103 (11). pp. 6120-6135. ISSN 00027820

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Abstract

ZrB2‐ZrCx composites were produced using Zr:B4C powder mixtures in the molar ratios of 3:1, 3.5:1, 4:1, and 5:1 by reactive hot pressing (RHP) at 4‐7 MPa, 1200°C for 60 minutes. X‐ray diffraction analyses confirmed the formation of nonstoichiometric zirconium carbide (ZrCx) with different lattice parameters and enhanced carbide formation by increasing the Zr mole fraction. An increase in applied pressure from 4 to 7 MPa was responsible for the improved relative density (RD) of 4Zr:B4C composition from 86% to 99%. Microstructural studies on Zr‐rich composites showed a reduction in unreacted B4C particles and enriched elongated ZrB2 platelets. Reaction and densification mechanism in 4Zr:B4C composition were studied as a function of temperature increased from 600 to 1200°C at an applied constant pressure of 7 MPa. After 1000°C, <40 vol.% of unreacted Zr was observed during the densification process. Concurrently, low energies of carbon diffusion and carbon vacancy formation were found to enhance nonstoichiometric ZrCx formation, which was found to be responsible for the completion of the reaction. The plastic deformation of unreacted Zr was responsible for the densification of the ZrB2‐ZrCx composite. The results clearly showed that the applied pressure is five times lower than the reported values. Moreover, a temperature of 1200°C was sufficient to produce dense ZrB2‐ZrCx composites. The improved microhardness, flexural strength, fracture toughness, and specific wear rate were 8.2‐15 GPa, 265‐590 MPa, 2.82‐6.33 MPa.m1/2, and 1.43‐0.376 × 10−2 mm2/N, respectively.

Item Type: Article
Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
CHEMISTRY AND MATERIALS > Composite Materials
Depositing User: Smt Bhagya Rekha KA
Date Deposited: 23 Nov 2021 11:38
Last Modified: 23 Nov 2021 11:38
URI: http://nal-ir.nal.res.in/id/eprint/13390

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