Abstract
The gas sulfonitriding of steels in a nitrogen base atmosphere was investigated. Test pieces of JIS S45C and SCM440 steels were treated in an atmosphere of the N2, NH3 and H2S mixed gas at 843 K for 8.1-22.5 ks.
It was confirmed by X-ray diffraction that the surface products were Fe1−xS and Fe3N in each specimen. In the microstructure of the treated specimens, the compound layer was observed close to the surface and there was a porous layer over the compound layer. The hardness distribution of the treated specimens showed that the hardness gradually increased toward the inner layer and reached a maximum value. The thickness of the compound layer increased parabolically with treating time. From these results it was found that the gas sulfonitriding of steels by the use of the nitrogen base atmosphere was possible.
