Low Pressure Nitriding ALLNIT®

Detailed description

The ALLNIT® process, patented by BMI, is a special low-pressure gas nitriding treatment. The atmosphere used is made up of the following gases:

• Ammonia (NH3): this nitriding gas by its dissociation allows the intake of the nitrogen atomic element N* necessary for nitriding.
• Nitrogen (N2): this inert gas allows dilution of the nitriding power of the treatment atmosphere.
• Nitrogen protoxide (N2O): this strong oxidising gas acts as an ammonia dissociation / absorption accelerator.
• And possibly a carburising gas of the hydrocarbon or carbon monoxide type that can be added for nitrocarburising applications.

The treatment takes place at low pressure. The depression is maintained by the vacuum pump units while the injection of the nitriding mixture is controlled by mass flow meters. The nitriding working temperatures are standard; they are between 400 and 600°C.

The ALLNIT® low-pressure nitriding process covers all standard gas nitriding applications. It is therefore particularly suited to the treatment of general engineering parts: transmission and friction systems, cutting machines, press or extrusion tools, plastic injection equipment… The deep penetration of nitriding into cavities, associated with excellent chemical homogeneity of the system makes the formation of particularly dense and/or semi-bulk loads possible.

Like any type of nitriding, the ALLNIT® low-pressure nitriding treatment can be followed by a post-oxidation treatment aimed at obtaining a black surface layer. The industrial objective is twofold: to provide a surface that is resistant to mechanical and chemical stresses at the same time, and to thus improve the friction and corrosion-resistance features.

 

The ALLNIT® low-pressure nitriding process is optional throughout the BMI range of tempering and annealing furnaces of the B5_R family. These vacuum furnaces are hence called B5_RN.