of 274 cc/sec. Figure 14 provides the results from the permeability tests per- formed on coated specimens at various surfactant levels at the five seconds dip times. Figure 14 shows that increas- ing the overall coating deposit (proud layer above the origin and penetrated layer beneath) reduced permeability.
Additionally, it shows that the higher percent surfactant reduces permeabil- ity. Figure 15 illustrates how the per- meability number and the MQI number tracked the coating thicknesses for the proud layer and the subsurface pen- etrated layer. There was no clear rela- tionship between permeability and the subsurface penetrated layer thickness, whereas Figure 15 shows a strong cor- relation (r =0.97) between permeabil- ity and proud layer coating thickness. Figure 16 reveals that permeability and MQI tracked the dry coat weight well (r = 0.99).
Phase II Methodology and Findings—Sand Distribution Study
and tested in laboratory conditions. Ambient conditions were controlled: temperature at 21°C ± 1°C and rela- tive humidity at 50% ± 2 %.) To en- sure that the study was executed me- thodically, an experimental design of two different surfactant levels of re- fractory coatings with three different sand distributions was employed with 10 specimens per cell.
Preparation and Characterization of New Coating
The manufacturer collected a gallon of experimental refractory coating at 38% solids. This coating was divided equally with a different level of sur- factant added to each. This enabled two coatings of different surface ten- sion to be prepared. The levels of sur-
International Journal of Metalcasting/Spring 11
The testing procedure consisted of the following additional steps: Prepa- ration and characterization of new coating, robotic coating of speci- mens, measurement of coating thick- ness, thermal distortion testing (TDT) and observation of physical changes (Note: All specimens were prepared
Figure 15. Relationship between the permeability, MQI, and proud coating layer thickness.
Figure 14. Effect of %Surfactant on Coating Layer Thickness & Permeability (five sec dip).
Figure 16. Relationship between the permeability, MQI, and dry coat weight. 15
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