Abstract
M.Tech.
The mining industry exerts ever increasing demand for components with high wear resistance to
the extent that plain ferrous alloys are falling short. Innovative metal-matrix composites nonferrous
metals have been widely researched and used. Casting composites based on ferrous
alloys pose monumental challenges in casting. Firstly, the density differential results in large
resistant forces on the ceramic such that unless a rigid structure is configured, the less dense
ceramic floats on the metal stream. Secondly, the poor wetting properties between metal and
ceramic will result in inferior bonding of the matrix, hence separation of solids in service.This
study presents the feasibility of manufacturing ceramic based metal matrix composites (MMC)
for multi-purpose industrial application including wettability and the bonding between the matrix
and the composite. The cold rods of alumina positioned in the mould prior to casting cracked as
soon as they came in contact with hot metal. Because of the density difference between ceramic
and liquid metal the alumina tended to float under the influence of Ferro static pressure.
Infiltration of zirconia (ZrO2) and alumina (Al2O3) in ferrous matrix was investigated. Infiltration
of liquid metal in ceramic filters increased with porosity of filters i.e. greater infiltration occurred
in filters with larger pore volume fraction measured in terms of number of pores per linear inch
(ppi). Thus, there was high infiltration in casting with 10ppi followed by 30ppi and there was
poor infiltration in 50ppi ceramics. Infiltration increased with increasing temperature of the
ceramics. A temperature of 1000oC was found to be superior to 800oC. The wetting behaviour of
molten iron on the substrates of Al2O3 was investigated. Titanium in high chromium white cast
iron was found to improve the wetting characteristics on alumina. The wetting angle decreased
with increased titanium content. The wear properties of ferrous alloys used were not significantly
improved by the ceramic used to make the composite. Filters are produced by a deposition
process and hence are not densified for the purpose of manufacturing hard composites