Microstructural evolution of nanosized tungsten carbide during heatup stage of sintering of electroless nickel-coated nanostructured WC-Co powder
SCIE
SCOPUS
- Title
- Microstructural evolution of nanosized tungsten carbide during heatup stage of sintering of electroless nickel-coated nanostructured WC-Co powder
- Authors
- Jafari, M; Enayati, MH; Salehi, M; Nahvi, SM; Park, CG
- Date Issued
- 2014-08
- Publisher
- ELSEVIER SCI LTD
- Abstract
- In this research, microstructural evolution of nanosized tungsten carbide during heatup stage of sintering of a novel electroless nickel-coated nanostructured WC-Co powder was investigated. Toward this purpose, a mechanical milling process was executed on commercial microcrystalline WC-Co (mc-WC) to achieve nanostructured WC-Co (nc-WC) powder. Electroless nickel plating was performed on the asmilled powder to obtain nickel-coated nanostructured WC-Co (Ni/nc WC). The nc-WC and Ni/nc WC powders were subjected to cold-pressing in a uniaxial die followed by heatup stage of sintering from 25 degrees C to a temperature range of 1000-1300 degrees C under argon atmosphere. The microstructural characterizations were carried out by X-ray diffractometry (XRD), high resolution field emission scanning electron microscopy (HR FESEM) and high resolution transmission electron microscopy (HRTEM). The ball milling process resulted in the formation of nc-WC powder containing nanosized WC with average grain size of similar to 15 nm. A uniform nickel layer with a thickness of <100 am was formed around Ni/nc WC particles through nickel plating. A two-step grain growth trend was observed during heatup of nc-WC: a slow grain growth step at temperatures <= 1000 degrees C, which led to WC grain size of similar to 76 nm, and a rapid step by heating to the temperature range of 1100-1300 degrees C which caused a substantial increase in WC grain size to similar to 925 am. In contrast, WC grain size in Ni/nc WC sample varied in the range of similar to 15-250 nm with temperature rising from 25 to 1300 degrees C representing about 72% reduction in WC grain size for Ni/nc WC compared to nc-WC. In case of nc-WC, surface faceting of nanosized WC occurred upon heating to <= 1000 degrees C; meanwhile, on heating to 1100-1300 degrees C, the coalescence mechanism was operative accounting for the rapid grain growth. As for Ni/nc WC, surface faceting of WC grains was greatly suppressed. This led to the retardation of the coalescence mechanism, making it possible to form ultrafine-grained Ni/nc WC material. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
- Keywords
- Sintering; Carbides; Grain growth; Microstructure-final; Electroless plating; NANOCRYSTALLINE WC; GRAIN-GROWTH; MECHANICAL-PROPERTIES; CEMENTED CARBIDES; COMPOSITES; COATINGS; ALLOYS; SIZE; CONSOLIDATION; DENSIFICATION
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/14190
- DOI
- 10.1016/J.CERAMINT.2014.03.118
- ISSN
- 0272-8842
- Article Type
- Article
- Citation
- CERAMICS INTERNATIONAL, vol. 40, no. 7, page. 11031 - 11039, 2014-08
- Files in This Item:
- There are no files associated with this item.
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.