Effect of B4C reinforcement on microstructure, residual stress, toughening and scratch resistance of (Hf, Zr)B2 ceramics

Effect of B4C addition on the lower damage tolerance of spark plasma sintered (Hf, Zr)B2 based ceramics has been elucidated. Increased densification (from 89% to 95%) with B4C addition has elicited hardness and elastic modulus increase from 25 GPa to 38 GPa (52%) and 439 GPa–635 GPa (45%), respectiv...

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Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2020-10, Vol.796, p.140022, Article 140022
Main Authors: Bajpai, Shipra, Kundu, Rishabh, Balani, Kantesh
Format: Article
Language:English
Subjects:
Abrasion
Boron carbide
Ceramic-matrix composites (CMCs)
Ceramics
Compressive properties
Crack initiation
Cracking (fracturing)
Damage tolerance
Densification
Flexural strength
Fracture mechanics
Fracture toughness
Hardness
Microcracks
Microstructure
Modulus of elasticity
Porosity
Residual stress
Scratch resistance
Scratching
Sintering
Spark plasma sintering
Synergistic effect
Wear mechanisms
Wear rate
Zirconium
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Summary:Effect of B4C addition on the lower damage tolerance of spark plasma sintered (Hf, Zr)B2 based ceramics has been elucidated. Increased densification (from 89% to 95%) with B4C addition has elicited hardness and elastic modulus increase from 25 GPa to 38 GPa (52%) and 439 GPa–635 GPa (45%), respectively. Systematic 3–9 vol% B4C addition resulted in an increased fracture toughness (from 2.2 MPa m0.5– 4.4 MPa m0.5) and flexural strength (from 320 MPa to 357 MPa) compared to that of (Hf, Zr)B2 due to synergistic effect of solid solutioning and compressive residual stresses generated around reinforcement. The decreased wear rate (from 0.163 mm3/N.m to 0.061 mm3/N.m) with optimal B4C addition, affirms enhanced damage tolerance of (Hf, Zr)B2 composite. Enhanced cracking and fracture in (Hf, Zr)B2 shifts to abrasion induced restricted micro-cracking as micro-scratch wear mechanism with B4C addition. Estimated elastic-modulus and extracted scratch-hardness are correlated with microstructural attributes of porosity, phase content and residual stress in (Hf, Zr)B2 composites. •Spark plasma sintering of dense (up to 95%) HfB2-ZrB2-B4C composites.•Fracture toughness doubled to 4.4. MPa.m0.5 in HfB2-ZrB2-9 vol% B4C.•Modelling the effect of solid solutioning on estimated elastic modulus.•Estimating scratch toughness/hardness and correlating to damage mechanics.•60% increased damage tolerance with B4C addition in HfB2-ZrB2 composites.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2020.140022