Figure 9 illustrates the coating layer thicknesses measured from the sectioned specimens dipped for five seconds at the various surfactant levels. In addition, Figure 10 illustrates the relationship between the proud layer deposits and the surfactant levels at different dip times. From these figures a trend in proud layer deposition with dip time and surfactant level is observed. The thickness in proud layer deposition increases with surfactant level at equal dip time. It also in- creases with dip time at equal surfactant levels for the 0.35% and 0.25% coatings. The results indicate that a thicker proud layer could be obtained by either increasing the surfactant level of the coating for a given dip time or increasing the dip time at a given surfactant level. However, due to the large standard deviations in the data, the differences observed were not found to be statistically different, so additional work is required to confirm this finding.
Permeability and MQI Testing
Permeability and MQI data provides a measure of the speci- men’s venting characteristics; however this data will be re- lated to the coating thickness measurements.
Materials:
Coated and uncoated PUCB disc-shaped specimens. Equipment:
Gerosa Simpson permeability tester (Figure 11), Disa George Fisher MQI (Figure 12), specimen holder designed and fabricated at Western Michigan University (Figure 13)
Permeability is a measure of gas flow through a porous me- dia such as mold or core sand. It is calculated by the perme- ability tester in Equation 1.3
Figure 9. Relationship between OVERALL coating deposits in five second dip time specimens at various surfactant levels (avg. of 30 measurements obtained by taking 10 measurements/specimen and three specimens measured/condition).
Figure 10. Relationship between proud layer and dip time at various surfactant levels (avg. of 30 measurements obtained by taking 10 measurements/specimen and three specimens measured/condition)
International Journal of Metalcasting/Spring 11 13
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