Abrasion-resistant surface finishes on metal enclosures
Composite coatings having improved abrasion and dent resistance are described. According to some embodiments, the composite coatings include an outer hard layer and an intermediate layer between the outer hard layer and a metal substrate. The intermediate layer can have a hardness that is less than the hard outer layer but greater than the metal substrate. In this arrangement, the intermediate layer can act as a structural support that resists plastic deformation when an impact force is applied to the coating. In some embodiments, the intermediate layer is composed of a porous anodic oxide material. In some embodiments, the outer hard layer is composed of a ceramic material or a hard carbon-based material, such as diamond-like carbon.
1. A housing for an electronic device, the housing comprising:
a metal portion; and
an abrasion-resistant coating overlaying the metal portion, the abrasion-resistant coating comprising:
a lapped metal oxide layer that defines a pore;
an organic colorant deposited within the pore by aqueous immersion of the metal oxide layer; and
a layer that overlaps the lapped metal oxide layer, the layer comprising a material comprising at least one of a carbide, a nitride, or a diamond-like carbon that is disposed within and seals the pore and overlays the organic colorant, the layer having a thickness between 0.5 micrometers to 3 micrometers.
2. The housing of claim 1 , wherein the metal oxide layer has a thickness between 8 micrometers to 30 micrometers.
3. The housing of claim 1 , wherein the pore is defined by a pore wall, and the material is bonded to an internal surface of the pore wall.
4. The housing of claim 1 , wherein the material comprises a diamond-like carbon.
5. The housing of claim 4 , wherein the metal oxide layer has a Vickers hardness ranging between 400 HV0.5 to 600 HV0.5.
6. The housing of claim 1 , wherein the layer has a polished exterior surface.
7. The housing of claim 1 , wherein a color of the organic colorant is matched to a color of the layer.
8. The housing of claim 1 , wherein the layer penetrates an upper portion of the metal oxide layer to a depth of at least 50 nanometers.
9. The housing of claim 1 , wherein the layer has a greater hardness than the metal oxide layer.
10. The housing of claim 1 , wherein the abrasion-resistant coating has a hardness between 1000 HV0.5 to 1500 HV0.5.
11. The housing of claim 1 , wherein the metal portion comprises aluminum.
12. A part for a portable electronic device, the part comprising:
a metal substrate; and
an abrasion-resistant coating disposed on the metal substrate, the abrasion-resistant coating comprising:
a lapped intermediate metal oxide layer that overlays the metal substrate, the lapped intermediate metal oxide layer defining a pore, the lapped intermediate metal oxide layer having a thickness between 8 micrometers to 14 micrometers;
an organic colorant deposited within the pore by aqueous immersion of the metal oxide layer; and
an external layer that overlaps the lapped intermediate metal oxide layer, the external layer comprising a material comprising at least one of a carbide, a nitride, or a diamond-like carbon that is disposed within and seals the pore and overlays the organic colorant.
13. The part of claim 12 , wherein the external layer has a thickness between 0.5 micrometers to 3 micrometers.
14. The part of claim 12 , wherein the material comprises a diamond-like carbon.
15. The part of claim 12 , wherein the abrasion-resistant coating has a hardness between 1000 HV0.5 to 1500 HV0.5.
16. A method of forming an abrasion-resistant coating over a metal portion, the abrasion-resistant coating comprising a metal oxide layer and a layer, the method comprising:
converting a portion of the metal portion to the metal oxide layer, the metal oxide layer having a thickness between 8 micrometers to 14 micrometers, wherein the metal oxide layer defines a pore;
infusing an organic colorant into the pore by an aqueous immersion process;
lapping the metal oxide layer; and
depositing the layer over the lapped metal oxide layer, wherein the layer comprises a material comprising at least one of a carbide, a nitride, or a diamond-like carbon that is disposed within and seals the pore, and overlays the organic colorant.
17. The method of claim 16 , wherein the layer has a thickness between 0.5 micrometers to 3 micrometers.
18. The method of claim 16 , wherein the material comprises a diamond-like carbon.
19. The method of claim 16 , wherein the abrasion-resistant coating has a hardness between 1000 HV0.5 to 1500 HV0.5.