Erosion resistant and hydrophobic article
An erosion resistant and hydrophobic article includes a core that has a first hardness and a surface on the core. The surface includes a plurality of geometric features that have a second, greater hardness. The geometric features define a surface porosity by area percent and a corresponding surface solidity by area percent. The surface includes a ratio of the surface solidity divided by the surface porosity that is 1.8 or greater. The geometric features and the ratio establish the surface to be hydrophobic, and the second, greater hardness and the ratio establish an erosion rate of the surface that is equal to or less than an erosion rate of the core under identical erosion conditions.
1. An article, comprising:
a core having a first hardness; and
a surface on the core, the surface including a plurality of geometric features having a second, greater hardness and defining a surface porosity by area percent (SP) and a surface solidity by area percent (SS), the surface including a ratio of SS/SP that is 1.8 or greater, the plurality of geometric features and the ratio establishing the surface to be hydrophobic such that the surface would not be hydrophobic in absence of the plurality of geometric features or the ratio, and the second, greater hardness and the ratio establishing an erosion rate of the surface that is equal to or less than an erosion rate of the core under identical erosion conditions such that the erosion rate of the surface would not be equal to or less than an erosion rate of the core in absence of the second, greater hardness or the ratio, wherein each of the plurality of geometric features extends along a respective central axis from a base at the core to a free end, the base defining a reference plane and the central axis being at a non-perpendicular angle to the reference plane, and wherein the non-perpendicular angles are non-equivalent.
2. The article as recited in claim 1 , wherein the plurality of geometric features include a plurality of cylindrical elements.
3. The article as recited in claim 1 , wherein each of the plurality of geometric features includes a height (h) extending from the base to the free end and a maximum width (w) extending perpendicular to the height to define an aspect ratio w/h that is 0.004-4.
4. The article as recited in claim 3 , wherein the plurality of geometric features include non-equivalent aspect ratios.
5. The article as recited in claim 1 , wherein each of the plurality of geometric features includes a cross-section taken perpendicular to the central axis, and the cross-section varies in area along the central axis.
6. The article as recited in claim 1 , wherein each of the plurality of geometric features includes an enlarged head at the free end.
7. The article as recited in claim 1 , wherein the non-perpendicular angle is less than 90° and greater than or equal to 20° .
8. The article as recited in claim 1 , wherein the free end has a surface that is sloped relative to the reference plane.
9. The article as recited in claim 1 , wherein the ratio is 15.7 or less.
10. The article as recited in claim 1 , wherein the plurality of geometric features are made of a metallic material.
11. The article as recited in claim 1 , wherein the plurality of geometric features are made of a material selected from the group consisting of polymer material, ceramic material, intermetallic material and combinations thereof.
12. The article as recited in claim 1 , wherein the core is made of a material selected from the group consisting of polymer material, metallic material, ceramic material and combinations thereof.
13. The article as recited in claim 1 , wherein the core and the plurality of geometric features are made of respective materials that have equivalent material composition.
14. The article as recited in claim 1 , wherein the core has an airfoil shape.
15. The article as recited in claim 1 , wherein the plurality of geometric features include a first group of geometric features at a first non-perpendicular angle and a second group of geometric features at a second, different non-perpendicular angle.