Bibliography: pages 147-152. / This thesis examines the fracture toughness behaviour of a series of cemented carbides
having carbide grain sizes between 0.35f.Lm and 4f.Lm, cobalt contents ranging from 6 to
15wt%, and vanadium carbide contents from 0 to 0.8wt%. A series of twenty-four
ultrafine WC-Co alloys were sintered from powders produced through three different
production routes, namely, the spray conversion process and two variations of the
conventional powder production methods. A further twelve WC-Co alloys with three
different carbide grain size distributions were produced through conventional powder
metallurgy processes.
Two different fracture toughness test methods have been used to determine the
toughness measurements, namely, the Palmqvist Indentation test and the Short Rod
test. A Terra Tek Fractometer machine was used to automatically determine the Short
Rod toughness values. The Palmqvist testing was carried out on a Vickers hardness
machine using indenting loads of 20, 30 and 50kg. The Palmqvist crack lengths were
measured by summing the individual crack lengths emanating from the corners of the
hardness indentation. These crack lengths were used in a formula developed by Shetty
et al., to calculate the Palmqvist fracture toughness. The influence of annealing at
800°C and 900°C on the Palmqvist crack lengths has also been assessed.
Microstructural parameters have been determined using ASTM procedures and
microscopy techniques and the influence of these parameters on the fracture toughness
has also been assessed.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/20181 |
| Date | January 1999 |
| Creators | Sacks, Natasha |
| Contributors | Allen, Colin |
| Publisher | University of Cape Town, Faculty of Engineering and the Built Environment, Centre for Materials Engineering |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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