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Challenges in brazing large synthetic diamond grit by Ni-based filler alloy
Prithviraj Mukhopadhyay, D. Raghava Simhan,
Published in Elsevier Ltd
2017
Volume: 250
   
Pages: 390 - 400
Abstract
Large size D711 synthetic single crystal diamonds are vacuum brazed with medium carbon steel using a Ni-Cr-Fe-B-Si alloy and inherent difficulties are critically investigated. Although, the alloy shows appreciable wetting on diamond at the brazing temperature of 1050 °C, micro-cracks develops and pronounces at the bond level in all as-brazed samples. The crack is not arrested even by using cooling rate, as slow as 5 °C/min. The large difference in Young's modulus and thermal expansion coefficient of the substrate, alloy and grit results in unfavorable tensile residual strain on diamond at bond level, causing detrimental stress. Formation of a partially coherent chromium iron carbide phase is identified which seems to facilitate the micro-crack formation under residual stress. The residual stress distribution at the interface region is mapped through finite element analyses. No noticeable difference in the strength of joint is recorded on reducing the cooling rate, up to 5 °C/min. Failure pattern of grits suggests a predominant bond-level breakage of diamond grits, indicating prevalence of residual stresses at bond level. The (110) crystallographic plane of diamond suffers significant graphitization at higher temperatures, even under a very high vacuum environment. © 2017 Elsevier B.V.
About the journal
JournalData powered by TypesetJournal of Materials Processing Technology
PublisherData powered by TypesetElsevier Ltd
ISSN09240136
Open AccessNo
Concepts (32)
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    Alloy steel
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    Binary alloys
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    Brazing
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    Carbides
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    Carbon
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    Carbon steel
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    Chromium alloys
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    CONCRETE AGGREGATES
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    Cooling
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    Cracks
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    Diamonds
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    Elastic moduli
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    Finite element method
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    Graphite
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    Graphitization
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    Iron alloys
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    Nickel
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    Nickel alloys
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    Residual stresses
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    Silicon alloys
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    Silicon wafers
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    Single crystals
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    Thermal expansion
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    CONTROLLED COOLING
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    CRYSTALLOGRAPHIC PLANE
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    HIGH-VACUUM ENVIRONMENTS
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    Medium-carbon steels
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    MICROCRACK FORMATION
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    NI-CR ALLOYS
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    SYNTHETIC SINGLE CRYSTALS
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    Thermal expansion coefficients
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    SYNTHETIC DIAMONDS