US Patent 9219803 Housing and electronic device using the same

A housing includes a substrate, a transition layer disposed on the substrate, and a color layer disposed on the transition layer. The transition layer is a layer of titanium-nitride and M-nitride, wherein the M is chromium, aluminum, or silicon. The color layer is a titanium-aluminum-nitride layer. The color layer provides the appearance of enamel on the exterior of the housing. The transition layer enhances the hardness of the housing. An electronic device using the housing is also described.