Nelson Mandela Metropolitan University
Hashe, Nobom Gretta.
Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals.
Degree: PhD, Faculty of Science, 2007, Nelson Mandela Metropolitan University
This thesis contains the results of a study focused on cubic carbide and carbonitride grain growth retardation in hardmetals. Large additions of VC, or VC and TiC, or (W,V)C were made to the WC-Co hardmetal, which was then sintered in vacuum or nitrogen. The effectiveness of Ti as the grain growth inhibitor, and the influence of nitrogen sintering on grain coarsening were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffractrometry (XRD) and atom probe field ion microscope (APFIM). Analysis of vacuum-sintered WC-VC-Co revealed that the cubic carbide grains have a core-rim structure. Ti was found to be a core-rim inhibitor in vacuum-sintered WCVC- TiC-Co. The average cubic carbide grain size distribution for the vacuumsintered materials was narrowed in the Ti-containing hardmetal. The nitrogen-sintered WC-VC-TiC-Co consisted of two phases of cubic carbonitride, one with high Ti-content and the other with high (W,V)-content. The surface region of the nitrogen-sintered WC-VC-TiC-Co was covered with a cubic carbonitride phase. Similar phenomena was observed in nitrogen-sintered WC-VC-Co where two types of carbonitrides were found, those with high V-content and the others with low Vcontent. A gradient zone, consisting of fine WC grains in a Co-rich binder and free from cubic carbonitride grains, was created in the surface region. The nitrogensintered materials consisted of a narrow grain size distribution. The use of (W,V)C as a starting powder affected the mechanical properties of the material with the WC-(W,V)C-Co material being the hardest of those produced in this study. Addition of (W,V)C powder to WC-Co was shown to be the most effective way to limit the cubic carbide grain size during sintering and produce a hard material. The cubic carbide grain size in the material produced this way was the smallest of all studied
Advisors/Committee Members: Neethling, J H Prof, Berndt, P R Dr.
Subjects/Keywords: Carbides; Hard materials
to Zotero / EndNote / Reference
APA (6th Edition):
Hashe, N. G. (2007). Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals. (Doctoral Dissertation). Nelson Mandela Metropolitan University. Retrieved from http://hdl.handle.net/10948/522
Chicago Manual of Style (16th Edition):
Hashe, Nobom Gretta. “Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals.” 2007. Doctoral Dissertation, Nelson Mandela Metropolitan University. Accessed March 19, 2019.
MLA Handbook (7th Edition):
Hashe, Nobom Gretta. “Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals.” 2007. Web. 19 Mar 2019.
Hashe NG. Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals. [Internet] [Doctoral dissertation]. Nelson Mandela Metropolitan University; 2007. [cited 2019 Mar 19].
Available from: http://hdl.handle.net/10948/522.
Council of Science Editors:
Hashe NG. Characterization of WC-VC-Co and WC-VC-TiC-Co hardmetals. [Doctoral Dissertation]. Nelson Mandela Metropolitan University; 2007. Available from: http://hdl.handle.net/10948/522