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Open AccessArticle

Influence of Grain Growth Inhibitors and Powder Size on the Properties of Ultrafine and Nanostructured Cemented Carbides Sintered in Hydrogen

1
Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, Zagreb 10000, Croatia
2
Alfa tim d.o.o., Čulinečka cesta 25, Zagreb 10040, Croatia
*
Author to whom correspondence should be addressed.
Academic Editor: Soran Birosca
Metals 2016, 6(9), 198; https://doi.org/10.3390/met6090198
Received: 8 July 2016 / Revised: 19 August 2016 / Accepted: 19 August 2016 / Published: 24 August 2016
(This article belongs to the Special Issue Process-Structure-Property Relationships in Metals)
The influence of grain growth inhibitors and powder size on the microstructure and mechanical properties of ultrafine and nanostructured cemented carbides was researched. Three different WC powders, with an addition of different type and content of grain growth inhibitors GGIs, VC and Cr3C2 and with dBET grain sizes in the range from 95 to 150 nm were selected as starting powders. Four different mixtures with 6 and 9 wt. % Co were prepared. The consolidated samples are characterized by different microstructural and mechanical properties with respect to the characteristics of starting powders. Increased sintering temperatures led to microstructural irregularities in the form of a discontinuous WC growth, carbide agglomerates and abnormal grain growth as a consequence of coalescence via grain boundary elimination. The addition of 0.45% Cr3C2 contributed to microstructure homogeneity, reduced discontinuous and continuous grain growth, and increased Vickers hardness by approximately 70 HV and fracture toughness by approximately 0.15 MN/m3/2. The reduction of the starting powder to a real nanosize of 95 nm resulted in lower densities, and significant hardness increase, with a simultaneously small increase in fracture toughness. The consolidation of real nanopowders (dBET < 100 nm) solely by conventional sintering in hydrogen without isostatic pressing is not preferred. View Full-Text
Keywords: ultrafine and nanostructured cemented carbides; grain growth inhibitors; powder size; sintering temperature; microstructural characteristics; mechanical properties ultrafine and nanostructured cemented carbides; grain growth inhibitors; powder size; sintering temperature; microstructural characteristics; mechanical properties
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Aleksandrov Fabijanić, T.; Jakovljević, S.; Franz, M.; Jeren, I. Influence of Grain Growth Inhibitors and Powder Size on the Properties of Ultrafine and Nanostructured Cemented Carbides Sintered in Hydrogen. Metals 2016, 6, 198.

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