NANOCRYSTALLINE CEMENTED CARBIDES SINTERD BY THE PULSE PLASMA METHOD

Andrzej Michalski 1Dariusz Siemiaszko 

1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland

Abstract

WC-Co carbides are usually produced by sintering with the participation of a liquid cobalt phase. However, the sintering of nanocrystalline WC-Co powders in the presence of a liquid cobalt phase results in the WC grains growing out. For example, if a powder with an initial grain size of about 10nm is subjected to conventional sintering, the WC grain size usually increases to about 500nm, and even with the use of growth inhibitors – to about 300nm.

The study presents the results of examinations of the structure and properties of nanocrystalline cemented carbides consolidated by the pulse plasma sintering method (PPS). The sintered nanocrystalline carbides were produced of a mixture of WC5wt.% Co powders with an average WC grain size of about 100nm. The sintering process was carried out at a temperature of 1200oC under a load of 50MPa for 5min. The thus sintered carbides had an average crystallite size of about 120nm, a density of 15.2g/cm3, hardness of 2000HV30 and the stress intensity factor KIC = 12.6MPa*m1/2. The hardness and resistance to brittle fracture of the WC5wt.%Co carbides sintered by PPS are higher than those of carbides sintered by the conventional methods with the participation of a liquid cobalt phase. For example, a conventionally sintered carbide (WC+6wt.%Co) with an average WC grain size of 700nm has a hardness of 1860HV30 and a stress intensity factor KIC of 8.6MPa*m1/2.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium I, by Dariusz Siemiaszko
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-18 11:26
Revised:   2009-06-07 00:44
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