Particle Size and Shape Characterization of Refractory Coating Materials

It is well known that the refractory Lost Foam Casting (LFC) coating has been one of the critical factors controlling the quality of final metal casting. In order to avoid defects caused by LFC coating failures, the refractory coating needs to be well controlled to provide sufficient mechanical and transport properties during the casting process. The characterization of the particles in the refractory coating is an important means to optimize and control dried coating properties. In this study, a number of commercial particle sizing instruments based on different theoretical backgrounds are evaluated for comparison purpose. These techniques include Laser Light Scattering, Single Particle Optical Sensing, Sedimentation, Electrical Sensing Zone and Imaging Analysis. In addition, a quantitative approach of characterizing particle shape is also investigated. Experimental results indicate that different particle sizing techniques result in large differences of the interpreted particle size information. Primarily, the non-spherical shapes of the particles in Lost Foam Casting coating influence the particle size results depending on the measurement techniques. This paper discusses the advantages and disadvantages of each particle sizing technique and suggestions for practical implementation for lost foam foundries.