Controlled thermogasocyclic nitriding processes

Abstract

The existing basic nitriding methods do not exploit many of the potential opportunities. To intensify it and increase its efficiency, this paper considers and proposes a new method of low-temperature nitriding, which makes it possible to optimise the classical process and reduce the consumption of ammonia from 2 to 10 times, reduce the nitriding time by 4-6.5 times with an increase in the thickness of the diffusion layer by 2-6 times without reducing the physical and mechanical properties. During the experiment, gas-cyclic and thermogasocyclic nitriding of armco iron was carried out on an experimental setup, which included a system for monitoring and maintaining the temperature in the working volume, a gas supply system, monitoring the flow rate and degree of ammonia dissociation, cleaning and drying gas, as well as two electromagnetic gas valves controlled from the control panel, allowing the processes to be carried out automatically. As a result, a new method of low-temperature nitriding has been developed – under the conditions of a thermo-gas cycle. This method consists in periodic alternation of saturation cycles during flow nitriding and resorption of the nitrided layer with the maximum possible decrease in the saturating capacity of the atmosphere. The proposed new method of thermogasocyclic nitriding is a new, effective hardening technology that allows to reduce the consumption of saturating gas and emissions into the atmosphere by up to 10 times, the nitriding time by 4-6.5 times, and also to increase the thickness of the diffusion layer by 2-6 times without reducing the physical and mechanical properties. A new technological parameter has been established – the duration of half-cycles, which allows simply and effectively regulating the phase composition and structure of the layer in order to obtain the required physical and mechanical properties.

Keywords

• nitriding
• thermo-gas cycles
• duration of the half-cycles
• saturation
• denitriding