Fundamental study on microstructure and physical properties of fluidised bed and rainfall sanding ceramic shells

The investment casting technique has advantages in the production of quality components and key benefits of accuracy, versatility and integrity. The mechanical performance of the ceramic shell is fundamental to the quality of the finished component. Two main techniques are used in the casting industry for the application of stucco material: rainfall sanding and fluidised bed. Work was carried out to characterise the fundamental difference in physical structure and mechanical properties of shells produced by both techniques. Stucco application within samples prepared by fluidised bed showed a tendency for the particles to be parallel to the ceramic surface, while in samples prepared by rainfall sanding the particles were more random and embedded into the slurry layer resulting in a thinner total shell build. Stress-strain curves generated form fired samples prepared by fluidised bed demonstrated a certain degree of non-brittle fracture, where this is not the case for rainfall sanding produced material. It is suggested that this is related to the manner in which cracks propagate through in the fluidised bed structure during testing. A relatively larger proportion of through stucco fracture was found in rainfall sanding produced samples in comparison to that in fluidised bed produced samples.