Abstract
Disparities prevail among the reported hardness and fracture toughness values for hard and brittle materials. A better understanding of the physical nature of hardness and fracture toughness and a standardized technique for reliable measurements of these quantities is urgently needed. We strongly recommend the use of the measured hardness after the bend in the hardness versus load (H-FLoad) curve, when the hardness approaches its asymptotic value. The present work reports a systematic study of hardness and fracture toughness on moissanite (single crystal hexagonal silicon carbide, 6H-SiC) samples. The measurements were performed over a broad load range from 0.49 to 294 N with the direct indentation method. Asymptotic values of Knoop hardness of HK = 19 GPa and Vickers hardness of HV = 22 GPa were reached at a high load between 50 N and 100 N. A consistent fracture toughness of KIC = 1.8 MPa•m1/2 was obtained across the entire load range. Our study presents experimental results for the hardness and fracture toughness of moissanite in the asymptotic-hardness region, and it raises concern regarding the application of moissanite single crystals as anvil material under shear/fconditions. Published by Elsevier B.V.
Original language | English |
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Pages (from-to) | 1669-1672 |
Number of pages | 4 |
Journal | Diamond and Related Materials |
Volume | 14 |
Issue number | 10 |
DOIs | |
State | Published - Oct 2005 |
Externally published | Yes |
Funding
This work was performed under the auspices of the U.S. Department of Energy (DoE) under contract W-7405-ENG-36 with the University of California. The Los Alamos National Laboratory research projects are supported by DoE-OIT_IMF and DoD/DoE_MOU programs.
Keywords
- Fracture toughness
- Hardness
- Silicon carbide