Metallurgy Question:

In general, the plaster used in gold investment casting is standard "plaster of Paris" or other such material it has a fine but inconsistent grain size and, for the most part, water based. The other parts you mentioned are generally a higher precision, the casting material is of a fine but consistent grain, high temperature, hard, and not always water based. This is especially important for turbine blades as the material from which they are cast is more difficult to fine finish than other metals and the precision is extremely important due to the speed of rotation. It would be safe to say that the latter could be used in place of the former but not the former in place of the latter. Hope this is helpful.