| 摘要 |
PURPOSE:To form a Ni-Cr alloy layer excellent in high temp. corrosion resistance, by diffusing and permeating Ni and, subsequently, Cr throughout the surface of a steel material in a gaseous phase. CONSTITUTION:An Ni halide or carbonyl compound is heated and evaporated in an Ni compound heating and evaporating apparatus 1 provided to the stock material heating zone A of a Ni-Cr alloy diffusion and permeation treatment apparatus and the obtained vapor is sent to a diffusion and permeation zone B by a route 2. A steel material to be treated is heated to 1,000-1,300 deg.C in the treating zone B and the vapor of the Ni compound is reduced to Ni on the surface of the steel material to deposite Ni which is in turn diffused and permeated into the surface of the steel material. The unreacted vapor of the Ni compound is cooled and recovered by the Ni compound recovery apparatus of a stock material recovery zone C. In the next step, a Cr compound such as Cr halide is evaporated in a heating and evaporating apparatus 9 to be introduced into the diffusion and permeation zone B to diffuse and permeate Cr into the surface of the steel material into which Ni is permeated and an outermost layer comprising a Cr-Ni alloy containing Cr in concn. higher than that of Ni is formed to enhance the high temp. corrosion resistance of the steel material. The unreacted vapor of the Cr compound is recovered by the Cr recovery apparatus of the stock material recovery zone C. |
