| 摘要 |
The specification discloses a method and apparatus enabling the formation of a diffusion surface layer on a surface of a metal substrate, typically a ferrous based metal substrate, wherein in a first stage in a first fluidized bed furnace, a diffusion zone is formed extending inwardly from the surface of the metal substrate in which nitrogen has been diffused to form a nitride or carbo nitride inner zone and an outer white layer that is substantially free of porosity, treating the substrate formed in the first stage to prevent formation of or remove any surface oxide on the surface of the substrate, and in a second stage separate from the first stage, holding the thus treated substrate in a fluidized bed furnace operated under an inert atmosphere and fluidized by a flow of inert gas or gases, the substrate in the fluidized bed furnace being treated in the presence of a halide gas and a particulate metal or metal alloy.
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