| 摘要 |
When producing parts by powder metallurgy methods a metallic powder (3) is compressed to a basic porous blank or so called green preform, which by isostatic hot-pressing or forging in a tool is further compressed to the shape of the required part. In order to increase the wear resistance of the part the green preform is before hot-pressing or forging exposed to a gas mixture in a so called CVD-process (Chemical Vapour Deposition). During the exposure to the gas mixture a thin layer of hard material (6) is deposited on the surface and in the pores (4) of the green preform. The tool for hot-pressing or forging is protected from wear by depositing in the CVD-process an additional thin layer (7) on the top of the first layer of hard material (6). This additional layer is softer than the first layer and could preferably be of the same kind as the metallic powder. |
