| 摘要 |
PURPOSE:To form a local covering in short time at a low cost without post working by concealing the non-film part of a work with a cover and closing the spacing between the cover and the work by a difference in the coefft. of thermal expansion between said cover and material to be worked in the stage of forming the film. CONSTITUTION:The non-film part of a circular cylindrical material 5 to be worked is locally concealed by a cover 9. The cover 9 is formed of an ''Invar'' alloy and has he inside diameter slightly larger than the outside diameter of the material. Such material is set on the tray 7 in a reaction furnace and the inside of the furnace is heated. Only the gaseous H2 is passed until the reaction temp. is attained. The material 5 expands thermally in an equal direction but the cover 9 does not expand thermally. The spacing between the material 5 and the cover 9 is thereby closed and the part of the material 5 except the exposed part can be shut off from the reactive gaseous atmosphere. If the temp. is lowered after the formation of the film, the material 5 restores the original size and can be therefore easily removed from the cover 9. |
