In view of problems commonly encountered in production operation of plasma nitriding furnaces made in China, an improved
design was brought forward to cot down heat loss from the furnace wall, enhance load-bearing capacity of the furnace bottom and increase reliability of the electrode connections. In the new design, most of the water-cooling cavity in the furnace wall was substituted by a vacuum heat insulating cavity. This vacuum cavity can obstruct heat loss during heating, promote convection cooling when filled up with nitrogen during cooling, and with the help of a
fast cooling unit, raise the cooling rate of the workpiece after nitriding. The bottom of the furnace was rockered which exhibits greater load-bearing capacity and uniforms gas flow in the furnace. A labyrinthine shielding of cathode was employed to shield the melt cast insulating mica entirely inside a steel cover, avoiding damage from electric discharge. The improved sealing of cathode with the bottom of furnace was also tight and safe. Production operation has shown that the newly designed
plasma nitriding furnace is of low heat loss, high load-bearing capacity and easy maintenance. The cathode has been in operation for more than three years without any troubles. Thirty percent of production rate can be increased compared with conventional plasma nitriding furnaces.