| 摘要 |
PURPOSE: To improve operability and to reduce kinds of required raw materials by allowing powdery NH4 Cl to contact with pure Cr grains, heating them in an inert gas atmosphere to generate Cr containing gas and allowing the generated gas to contact with the surface of a metallic material to be treated to subject the surface to diffusion coating with a Cr diffusion layer. CONSTITUTION: Powdery NH4 Cl12 is scattered and stuck on pure Cr grains 11 so as to cover the Cr grains 11 with the powdery NH4 Cl12 in a reaction vessel 2 and also, in such a way that nonuniformity in layer thickness of the NH4 Cl12 is effected to form recessed and projecting parts 13 in the vessel 2. At this time, the pure Cr grains 11 have grain diameter more than about 10 times as much as the particle diameter of the powdery NH4 Cl12 and te packing amount of the pure Cr grains 11 is about 10 times as much as that of the NH4 Cl12 by weight. Then, a metallic material 3 to be treated is packed in the reaction vessel 2 in a state of the metallic material 3 is floating on the powdery NH4 Cl12. Thereafter, an inert gas is injected into the reaction vessel 2 to form an inert gas atmosphere inside the reaction vessel 2 and the contents of the reaction vessel 2 is heated to about 1,052 deg.C to generate a Cr containing gas (such as gaseous chromium chloride) and thereby a chromium diffusion coating layer 16 having an about 50μm thickness s formed on the surface of the metallic material 3 to be treated.
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