The physical mechanism responsible for impact ice adhesion variations for different coatings is not well understood. This research examines the effects of surface characteristics on ice adhesion strength for three erosionresistant materials. The materials tested were titanium grade 2, titanium aluminum nitride coated on titanium grade 2, and titanium nitride coated on titanium grade 2. The surface roughness of the material contributed to the ice adhesion strength but did not explain the variation in ice adhesion strength for materials at similar surface roughness values. To compare the materials, the ice adhesion strength was divided by the environmental temperature to allow for the comparison of ice adhesion measured at varying temperature conditions. The new quantity was called temperature-adjusted adhesion strength. When the surface roughness of the titanium grade 2 substrate increased from 26.4 to 86.1 in:Ra, the temperature-adjusted adhesion strength increased 29%. The titanium nitride temperature-adjusted adhesion strength increased 63% when the surface roughness increased from 23.2 to 66.7 1/4 in:Ra, and the titanium aluminum nitride temperature-adjusted adhesion strength increased by a factor of four. At the lowest surface roughness values tested, the temperature-adjusted adhesion strength of titanium nitride was 31% higher than the uncoated titanium grade 2 substrate, and the titanium aluminum nitride was 40% lower than the uncoated titanium grade 2. The temperature-adjusted adhesion strength of the coatings was58%higher than the uncoated substrate across the three surface roughness values. Mechanical clamping was determined to be the primary mechanism for ice adhesion strength. Macrostructures with "cliff"-like structures, observed on the coatings via scanning electron microscope visualization, increased the ice adhesion strength over what would be predicted from a surface roughness characterization. These structures also explained the 40% increase in ice adhesion strength of a material subjected to oxidation.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering