Refractory materials are substances or minerals that have high melting points, and they are difficult to fuse except at very high temperatures. They are processed at high temperatures and are intended for high temp applications. According to the Committee C-8 if the American Society for Testing and Materials (ASTM) refractoriness has been defined as, "the capability of maintaining the desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use."
A refractory coating on the core or mold should have the following characteristics:
Sufficient refractory properties to cope with the metal being poured
Good adhesion to the substrate to prevent spalling
Be permeable to minimize air entrapment
Be fast in drying
No tendency to blistering, cracking or scaling on drying
Good suspension and remixing properties
Minimize core strength degradation
Provide adequate protection against metal penetration
Good stability in storage
Good covering power
Good application properties by the method chosen
Leveling well and minimizing runs and teardrops
In order for a high temp ceramic coating to achieve these characteristics, the coating must consist of:
Suspension agents (Rheology control system)
The melting temoerature of refractory matierals is an important characteristic, showing the maximum temperature of use. It represents funamental points in phase diagrams used in high temperature chemistry, metallurgy, ceramics, etc.
When it comes to high temp ceramic coatings, refractory materials are dispersed in the binder and constitute the skelton of the coating film. The increase the viscosity, density, and hardness of the coating film in order to reduce permeabilty.
Besides the characteristics that resist high tempertaures, refractory materials should exhibit other characteristics too. These include things like:
Suitable for particle shape, particle size, and partical size distribution
Chemically inert with molten metal
Not be readily better by molten metal
Not contain volatile elements that produce gas when heated
Heave consistent cleanliness and pH
Be compatible with new chemical binders as they develop
Using refractory coatings have many benefits, including:
Reduce or eliminate metal penetration
Reduce or prevent “burn-on”
Prevent erosion of sand by molten metal
Smoother surface finish
Improve overall casting quality
Lower cleaning costs
When it comes to high temp coatings, ITC 100 refractory work wonders for many applications, including kilns. The earliest known kilns date all the way back to 6,000 BCE; they were capacle of firing up to 1,652 degrees Fahrenheit (900 degrees Celsius). These refractory high temp ceramic coatings would have worked for kilns back then, and they certain do well with the kilns of today.