Abstract
The importance of foundry coating in improving the surface quality of castings cannot be over emphasized. The application of mould and core washes creates a high thermal integrity barrier between the metal and the mould resulting in the reduction of the thermal shock experienced by the sand system. These thermal shock leads to series of surface defects such as veining/finning, metal penetration, burn-on/in, scab, rat tail, erosion etc. The use of coatings reduces the tendency of occurrence of these defects. However, the understanding of the coating, its components, characteristics and mechanism of action is important. In this review, a detailed description of these topics and examples are provided where necessary. A potential area of research in foundry coating development, using sol-gel process is suggested. The application of sol-gel technology in the development of foundry coatings is a novel approach.
Highlights
Research in coatings for various applications such as aesthetics, corrosion protection, wear resistance, thermal barrier, self-cleaning, antifouling etc. have been very wide spread but not much is going on in the area of foundry coatings in recent times
There are other factors to be considered, such as the ability to vent off the gases produced during casting, economic use of a binder, non availability of sand with required grading, etc., these make the use of coatings the more practicable approach [1]
This paper provides a detailed understanding of the constitution of foundry coatings while providing alternatives to the foundry coating components depending on the metal to be cast and their properties and compatibility with sand properties such as grain size and grain size distribution and binder properties
Summary
Sol-gel technology is discovered in the late 1800s and extensively studied since the early 1930s. The application of sol-gel technology in the production of foundry coatings is a novel research area undertaken by our research group. Sol-gel technology is an area of materials science. It denotes a process by which largely inorganic polymers are synthesized through the formation of a colloidal suspension (sol) and gelation of the sol to form a network in a continuous liquid phase (gel). The final material produced in a room temperature synthesis is a porous glasslike solid, which is termed a xerogel [70]. This xerogel is the sol-gel component of the coating being produced and tested for foundry application. The low processing temperature; the possibility of changing the sol composition, thereby producing a change in film and coating microstructure and low processing cost compared to some other competitive process such as ceramic (powder) method, chemical deposition process etc [72]
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