A study of vitreous-bonded abrasive materials.
This thesis has focused primarily on the effect of bond and
workpiece composition on the performance of vitreous-bonded
alumina grinding wheels. The effect of bond composition
considered in this work can equally be applied to grinding
wheels which use silicon carbide (carborundum) as the
The bonds considered in this study are described as
sintering bonds (high clay content), used in silicon carbide
grinding wheels, - and fusible bonds (high glass content),
used in vitreous bonding systems suitable for use in
aluminium oxide grinding wheels.
The initial part of the research work deals with a review of
the mechanisms of grinding and the evaluation of wheel
performance. The effect of grinding conditions, abrasive
compositions, and workpiece material composition on the
mechanisms of grinding wheel wear in conventional wheels was
studied. The analysis of grinding wheel wear was examined
and compared with experimental data.
Reactions in grinding wheel bond materials were examined by
comparing theoretical equilibrium compositions with actual
reaction products using experimental techniques such as
x-ray powder methods and differential thermal analysis.
Experimental studies were carried out to investigate the
vitrification behaviour of sintering and fusible bonds.
This was achieved by examining the relationship between
theoretical equilibrium liquid and silica contents and
experimental vitrification conditions. A semi-empirical
model was developed for determining optimum firing
conditions for sintering and fusible bondsThe effect of bond composition on the strength of sintering
and fusible bonds, under fixed firing conditions, was
investigated. This resulted in some bonds failing by cracks
around quartz particles, whilst bonds with high glass
contents failed by a combination of pore-flaws. A model was
also developed which predicted the amount of quartz
remaining after heat treatment. The model was shown to be
accurate when compared with experimental data.
Based on the results of the experimental work on bond
characterisation, the effect of bond and workpiece
composition was compared with grinding wheel performance
data. This was achieved by grinding a variety of hardened
tool steels with abrasive segments manufactured with
optimised grades. An empirical model was developed which
showed that wheel wear was a function of bond strength and
the nature of complex carbides present in the microstructure
of the tool steels.