Characterization of NiAl with cobalt produced by combustion synthesis

Abstract

In this study, as an alloying element the effect of cobalt addition by 2.5 wt.% and 5 wt.% on the NiAl intermetallic compound produced by pressure-assisted combustion synthesis method was investigated. As starting materials aluminum powder with 15 mu m size, carbonyl-nickel 4-7 mu m size and cobalt powders 10-44 mu m size having 99%, 99.8% and 99.9% purity, respectively were used. The formation temperature of intermetallic compound for three different powders mixture determined by DSC analysis was approximately 654 degrees C. The production of NiAl was carried out in electrical resistance furnace in open air with a uniaxial pressure of 150 MPa at 1050 degrees C for 60 min. Optical and SEM studies showed that intermetallic compounds have low porosity and phase transformation has been completed. The distribution of alloying elements was confirmed by EDS analysis. The presence of NiAl and CoAl phases was determined by XRD analysis. The relative density of pure NiAl, NiAl + 2.5 wt.% Co and NiAl + 5 wt.% Co materials was 99.65%, 99.48% and 99.30% and the microhardness of materials was about 368 HV1.0, 398 HV1.0 and 425 HV1.0, respectively. (C) 2010 Elsevier B.V. All rights reserved.