The Nitriding Process in a Nitriding Furnace
A nitriding furnace is a specialized piece of equipment designed for nitriding treatments. It is characterized by low processing temperatures, short treatment durations, minimal workpiece deformation, resulting in components that possess a high fatigue limit excellent wear resistance.
Nitriding is a thermochemical heat treatment process in which nitrogen atoms are diffused into the surface layer of a workpiece within a specific medium at a specific temperature. Components that have undergone nitriding treatment exhibit exceptional resistance to wear, fatigue, corrosion, high temperatures.
During the process, ammonia gas is introduced into a vacuum-sealed stainless steel retort housed within the nitriding furnace. The furnace is then heated to 520°C held at this temperature for a specific duration—ranging 3 to 90 hours, depending on the workpiece material the required nitriding depth. This process creates a nitrogen-enriched hardened layer on the workpiece surface, thereby imparting high hardness, superior wear resistance, a high fatigue limit, excellent durability.

Operating Procedures:
1. Prior to nitriding, the molds workpieces must have already undergone a normalizing quenching tempering heat treatment.
2. Thoroughly clean the surface of the workpiece using gasoline alcohol; ensure that no rust spots, oil stains, dirt remain.
3. Once the workpiece has been loaded into the furnace, symmetrically tighten the bolts securing the furnace lid to ensure a tight seal.
4. Circulate cooling water through the inlet ports on both the furnace retort the furnace lid to provide water cooling. For the piping on the furnace lid, the lower port serves as the water inlet the upper port as the outlet; the furnace retort utilizes a separate inlet outlet. All water pipes on the furnace lid may be connected in series—following the principle of "low-in, high-out"—allowing for a single water inlet a single water outlet for the entire lid assembly.
5. Before raising the temperature, introduce nitrogen gas to purge the furnace atmosphere; during this purging phase, the gas flow rate should be at least double the rate used during the actual nitriding process. After purging for 10 minutes, set the temperature controller (as shown in the figure below) to 150°C toggle the automatic heating switch to the "ON" position; continue purging while heating to 150°C, holding this temperature for 2 hours. Next, set the temperature controller to 530°C reduce the ammonia gas flow rate to maintain a positive pressure within the furnace, ensuring a slight upward flow of gas at the exhaust port. Once the furnace temperature reaches 530°C, perform nitriding at a constant temperature constant flow rate for 3 to 20 hours. Subsequently, slightly increase the ammonia gas pressure to maintain a moderate pressure at the exhaust, continue nitriding for another 4 to 70 hours. Then, reduce the ammonia gas pressure again perform a denitriding step for 1 to 2 hours. Finally, cut off the power supply stop heating; continue supplying a small amount of ammonia gas to maintain a positive pressure within the furnace until the temperature drops below 150°C, at which point the ammonia supply may be stopped the workpiece removed the furnace.