A number of variations may include a brake rotor having a surface oxide layer and methods of making the same.
1. A nitrocarburized ferrous brake rotor of a motor vehicle, wherein the brake rotor has disposed at a surface thereof an oxide layer comprising Fe 3 O 4 , and further comprising a compound zone including the oxide layer, the compound zone further comprising, generally subjacent the oxide layer, a first concentration of diffused nitrogen; and
a diffusion zone subjacent the compound zone, the diffusion zone comprising cast iron with a second concentration of diffused nitrogen lower than the first concentration of diffused nitrogen of the compound layer.
2. A nitrocarburized ferrous brake rotor of a motor vehicle, wherein the brake rotor has disposed at a surface thereof an oxide layer comprising Fe 3 O 4 , wherein the brake rotor further comprises:
a compound zone including the oxide layer, the compound zone further comprising, generally subjacent the oxide layer, predominantly of epsilon iron nitride Fe 3 N and a smaller volume of gamma prime iron nitride Fe 4 N; and
a diffusion zone subjacent the compound zone, the diffusion zone comprising iron base ferrous material with a lower concentration of diffused nitrogen than that of the compound layer,
wherein the iron base ferrous material comprises cast iron.
3. A nitrocarburized ferrous brake rotor of a motor vehicle, wherein the brake rotor has disposed at a surface thereof an oxide layer comprising Fe 3 O 4 , wherein nitrocarburized ferrous brake rotor comprises cast iron and wherein the oxide layer is constructed and arranged so the friction properties of the brake rotor are within four percent of the friction properties of a cast iron brake rotor not having been ntirocarburized nor having the oxide layer.
4. A brake rotor comprising:
at least a first brake rotor cheek comprising pearlitic cast iron and having a compound zone comprising an oxide layer comprising Fe 3 O 4 ; and generally subjacent said oxide layer is predominantly epsilon iron nitride Fe 3 N and a smaller volume of gamma prime iron nitride Fe 4 N; and
a diffusion zone disposed subjacent said compound zone, the diffusion zone comprising iron base ferrous material with a lower concentration of diffused nitrogen than that of said compound layer with the nitrogen in solid solution with the base ferrous material, further comprising a hat connected to the at least one rotor cheek, said hat having an exterior side; further comprising said exterior side of said hat having said ferritic nitrocarburized surface treatment defined by said compound zone and said diffusion zone.
5. The brake rotor of claim 4 , wherein said compound and diffusion zones collectively comprise a case, wherein said compound zone has a depth of substantially 0.015 millimeters, and wherein said diffusion zone has a depth of substantially 0.15 millimeters and wherein said compound zone has a hardness of substantially at least HRC 50 equivalent.
6. A nitrocarburized ferrous brake rotor of a motor vehicle, wherein the brake rotor comprises oxide layer comprising Fe 3 O 4 , and with the proviso that there is no antiseizing coating over the oxide layer, and comprising a compound zone including the oxide layer, the compound zone further comprising, generally subjacent the oxide layer, a first concentration of diffused nitrogen; and
a diffusion zone subjacent the compound zone, the diffusion zone comprising cast iron with a second concentration of diffused nitrogen lower than the first concentration of diffused nitrogen of the compound layer.
7. A nitrocarburized ferrous brake rotor of a motor vehicle, wherein the brake rotor has disposed at a surface thereof an oxide layer comprising Fe 3 O 4 , wherein nitrocarburized ferrous brake rotor comprises cast iron and wherein the oxide layer is constructed and arranged so the apparent friction of the brake rotor is four percent less than that of a cast iron brake rotor not having been ntirocarburized nor having the oxide layer.