| 摘要 |
PURPOSE: To improve abrasion resistivity and besides separation resistivity and corrosion resistivity by low temperature ion nitriding of the surface of a pipe shape part of austenitic stainless steel including molybdenum. CONSTITUTION: Austenitic stainless steel including molybdenum and nickel and consisting of chrome of ca. 16 to 20% and iron for the rest, for example SUS316, SUS316L, is used to execute low temperature ion nitriding at ca. 400 to 470 deg.C. As the nitride layer is mainly M4 N (M:Fe, Ni, Cr etc.), production of chrome nitride is suppressed and degradation of corrosion resistivity is prevented. Molybdenum content of 2 to 3% is desired for this. The ratio of nitrogen gas and hydrogen gas in the nitriding is set to be N2 : about 5 to 15vol%, H2 : about 95 to 85vol%. The thickness of the produced nitride layer of about 50μm is enough. By this, a pipe shape part having superior resistivity is obtained.
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