Author(s)

Kuk-Hyun Yeo, Sang-Gweon Kim, Jae-Hoon Lee, Jung-Hyun Kong, Masahiro Okumiya

Heat Treatment Technology R&BD Group, Korea Institute of Industrial Technology, Incheon, Korea.
Toyota Technological Institute, Nagoya, Japan.

Low temperature screen plasma technology, a high plasma density, through using a low energy supply, shows excellent effects on a low alloy chromium-molybdenum steel for plastic molds because it does not show a compound layer and a high surface hardness without a deterioration in matrix hardness. For interest about hardening depth, both the screen plasma nitriding and plasma nitro-carburizing processes were tested including nitrogen, hydrogen and a methane mixed gas environmental at 653 K, 713 K. The optical emission spectroscopy (OES) has been analyzed during screen plasma nitriding (SPN) and a nitro-carburizing process (SPNC) was proceeded at 713 K and the same pressure. I find it difficult to dissociate nitrogen molecules perfectly with neutral nitrogen atoms via the DC-plasma nitriding process. Therefore, the SPN and SPNC process have shown a high density of plasma species even though low temperature plasma conditions have a high peak intensity of H_β and H_γ in the results of the analysis by OES. The hardness value was measured with the micro-Vickers hardness tester after the SPN, SPNC process and the chemical composition of nitriding layers were traced by GDOES. The screen nitriding layer via the screen plasma technology has shown excellent properties with a thickness depth of about 850 ~ 900 HV without the deterioration of matrix hardness value.

Screen Plasma Technology, Plasma Nitro-Carburizing, Optical Emission Spectroscopy, Without Compound Layer, Chromium-Molybdenum Steel

Yeo, K. , Kim, S. , Lee, J. , Kong, J. and Okumiya, M. (2014) Trend of Nitriding on Chromium-Molybdenum Steel via Low Temperature Screen Plasma Technology. Advances in Materials Physics and Chemistry, 4, 141-152. doi: 10.4236/ampc.2014.48017.