Kazuto Hamaishi1, Hidekazu Sueyoshi2, Shigeru Kadomatsu2,Takayuki Shiomizu2 and Yoshihisa Ohzono3
1Kagoshima Prefectural Institute of Industrial Technology, Hayato-cho, Airagun, Kagoshima
In order to develop a method of gas nitriding of austenitic stainless steel SUS304 without chemical treatments, the steels were preheated in the atmosphere in a temperature range of 473 to 1273 K followed by nitriding in NH3 gas with a flow rate of 2.8 m3/h at 843 K for 20 h. The influence of atmospheric preheating on nitriding behavior was examined in connection with microstructures of the surface layers.
Atmospheric preheating in the temperature range of 673 to 1023 K results in the formation of a uniformly nitrided layer with the Vickers hardness of 1000 and the depth of 100 to 150 μm. X-ray photoelectron spectroscopy analysis suggests that the surface layer of the specimen preheated in the atmosphere in the temperature range of 673 to 1023 K is inferior in protective quality to that of the non-preheated specimen.
It is confirmed from the present results that gas nitriding of SUS304 is practicable without chemical treatments when atmospheric preheating is carried out in the temperature range of 673 to 1023 K.
(Received December 11, 1995)
gas nitriding, austenitic stainless steel, atmospheric preheating, surface layer, X-ray photoelectron spectroscopy analysis
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