A thesis submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, in
fulfilment of the requirements for the degree of Master of
Science in Engineering
Johannesburg, 1993 / The formation of VC, NbC, and Cr-carbide coatings on steels
immersed in molten borax baths containing carbide-forming
constituents has been known for some time. A study was made
of the formation of carbide coating on steel specimens
treated in molten borax cont.ad.Lnr.q ferro-vanadium and V20S
as bath additives. The prevalence of oxidizing or reducing
conditions in the bath was found to playa decisive role in
the formation of the VC layer. The influence of treatment
factors such as time, temperature, and bath composition on
the thickness of the coating was investigated. A detailed
investigation into the behaviour of baths containing V205
and Al was carried out in this regard. Microstructural
examination of coated specimens was performed using optical
and electron microscopy. Microhardness tests, X-ray
diffraction (XRD) and energy dispersive spectroscopy (EDS)
analyses were carried out in order to characterise the
layers produced.
The corrosion behaviour of the vanadf.um carbide coating was
evaluated by accelerated electrochemical means. Samples of
mild steel and EN9(O.5% C) steel were treated for various
lengths of time in order to obtain coatings of various
thicknesses. The corrosion resLst.ance of the carbide
coating was found to be superior to that of the untreated
base alloys.
Five diffet"ent tool steel materials were a.lso treated.
Microscopy examination and hardness testing of the VC
coated tool steels was performed in order to assess the
effects of treatment by this process on the bas~ material.
The austenitizing temperature and the nature of the
carbides in the matrix of the tool steels was found to play
an important role in this respect. / MT2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/23012 |
| Date | January 1993 |
| Creators | Fazluddin, Shahed Bhagga |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (209 leaves), application/pdf |
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