What are they? What is the difference between a castable product and a spray-on refactory or insulating-type product?
At last! Someone asks a question in my area of expertise (materials engineering)!
“Casting” is the process of pouring a liquid into a mold and solidifying it to make a part. Usually it refers to liquid metal processes, where you melt the metal, pour it into a refractory mold, and cool it.
“Refractory” loosely means a material with a high melting point or an insulating material. There are “refractory metals,” but when you use the word by itself, it usually means some kind of ceramic.
I would expect that a castable refractory product is a ceramic slurry (solid ceramic particles in suspension in a liquid). You pour it into a mold, and heat it to dry the liquid and probably sinter the particles (bind them together without melting them). It probably makes a moderately porous ceramic part.
A spray-on product is just what it sounds like - a similar ceramic slurry, that you spray onto a surface and dry. For most processes where spraying makes sense, it would be difficult to sinter, so it’s probably mechanically weaker than the castable product.