A Study on Utilization of LD Slag in Erosion Resistant Coatings and Polymer Composites

Abstract

Although a variety of metal and ceramic powders are used as coating material and as reinforcing fillers in polymeric resins, the use of industrial wastes for this
purpose has not been adequately explored. In view of this, the present investigation reports on the development and performance of new class es of
plasma sprayed coatings and polymer composites using Linz-Donawitz slag (LDS) as the primary material. This LDS is a major solid waste generated in huge quantities during steel making and its chemical analysis suggests the
presence of oxides of silicon, calcium and iron in it.
The research reported in this thesis broadly consists of two parts: The first part
has provided the description of the materials used, the experimental details and
the methods adopted for analysis of experimental results. This part has also
presented various physical and mechanical characteristics of the plasma
sprayed LDS based coatings and LDS filled epoxy and polypropylene
composites. An assessment of LDS as a potential coating material and a
particulate filler in polymers has been made by evaluating the physical and
mechanical properties of these coatings and composites under controlled
laboratory conditions. Effects of premixing of Al
2O3
and TiO
2
powders on the
physical and mechanical properties of LD slag coatings have also been
reported. The second part of the thesis reports on the erosion wear
characteristics of these coatings and composites. The wear response of LDS,
‘LDS + Al
2O3
’ and ‘LDS + TiO
2
’ coatings have been discussed separately.
Comparisons between the erosion characteristics of LD slag filled epoxy and
polypropylene composites with and without glass fiber reinforcement have also
been presented. Parametric analysis and wear response prediction has been
made for all the coatings and composites under this study using statistical
techniques namely Taguchi experimental design and artificial neural networks
(ANN). Correlations have been developed to predict the wear rate for these
coatings and composites under different test conditions.
x
This work suggests that LDS is eminently coatable and deposition of such
coatings using plasma spraying route is possible. These coatings possess
desirable characteristics such as good adhesion strength, hardness etc. This
work further establishes that LD slag can also be used as a functional filler in
both thermoset and thermoplastic polymers. These LD slag filled composites
possess very low amount of porosity and improved micro-hardness. They also
exhibit improved impact strength as compared to that of the neat polymers. The
tensile and flexural strength of the composites are affected by the weight fraction
of LDS in the composites. With improved hardness, these composites have the
potential to be used in wear related applications.
Erosion wear characteristics of LDS coatings and LDS filled polymer
composites have been successfully analyzed using Taguchi technique. Significant
factors affecting the erosion rate of these coatings and composites are identified
through successful implementation of this technique. Two predictive models; one
based on artificial neural networks (ANN) approach and the other on Taguchi
approach are proposed in this work. It is demonstrated that these models well
reflect the effects of various factors on the wear loss and their predictive results
are consistent with the experimental observations. Neural computation is
successfully applied in this investigation to predict and simulate the wear
response of these coatings and composites under various test conditions within
and beyond the experimental domain. The predicted and the experimental values
of erosion wear rate exhibit good agreement and validate the remarkable
capability of a well-trained neural network for these kinds of processes.