Cold-walled (double-walled water-cooled) systems were the first generation of plasma nitriding furnaces. This technology is also a vacuum-based process but employs the principle of glow discharge to provide energy for heating and nitriding at one time. Therefore, the independent control of the temperature stability and the nitriding intensity is not possible because both processes are using the same energy source—the plasma.
The hot-wall plasma nitriding furnaces, the next generation of cold-wall ion nitriding systems, are mainly used and built now. This system ensures optimal nitriding quality by fulfilling the highest demands on temperature and nitriding process control. The big advantage of this technology is the separation of the control of the heating and the plasma nitriding parameters.
For more information, click on the link below (subscription required). Then scroll to Figure 26
R Schneider; R. Mesquita; H. Altena; T. Müller; P. Seemann, Processes and Furnace Equipment for Heat Treating of Tool Steels, ASM International, 2014, https://doi.org/10.31399/asm.hb.v04d.a0005958
