Attaining the Steady State of the Nitriding Potential after a Change of NH3 Atmosphere Flow Rate during the Gas Nitriding Process
来源期刊：材料热处理学报2004年第5期
论文作者：Piotr Wach Jerzy Michalski Nabil Tarfa Jan Tacikowski Tomasz Babul
关键词：nitriding processes; nitriding potential; NH3 atmosphere characteristics; stabilized stat;
摘 要：In single and multi-stage nitriding processes, each stage is characterized by the following parameters:temperature and time, type and composition of incoming atmosphere, as well as the set value of the nitriding potential. In the case of an atmosphere composed of raw ammonia and dissociated ammonia (NH3- NH3diss), the set value of the nitriding potential can be achieved by a change of the incoming atmosphere make-up, while in the case of atmospheres comprising NH3 and NH3 - N2 - by a change of the atmosphere flow rate. The time needed to reach a stabilized state, after the initiation of a change in the atmosphere gas mix can be assessed relatively easily. The problem is much more complex if we want to predict the time of reaching a new stabilized state following a change in atmosphere flow rate. The time of reaching stabilized state is, in this case, a complex function of the flow rate of the atmosphere which forces the potential change, and of temperature. This problem, in the case of the NH3 type atmosphere, is the subject of investigation in this work. Factors are discussed, affecting the rate at which stabilized state is reached by the system after the introduction of a disturbance, necessary to attain the required nitriding potential.
Piotr Wach1，Jerzy Michalski1，Nabil Tarfa2，Jan Tacikowski1，Tomasz Babul1
(1.Institute of Precision Mechanics, Warsaw, Poland;
2.Nitrex Metal Inc., 3474 Boul. Poirier, St-Laurent, Quebec, CANADA.)
摘要:In single and multi-stage nitriding processes, each stage is characterized by the following parameters:temperature and time, type and composition of incoming atmosphere, as well as the set value of the nitriding potential. In the case of an atmosphere composed of raw ammonia and dissociated ammonia (NH3- NH3diss), the set value of the nitriding potential can be achieved by a change of the incoming atmosphere make-up, while in the case of atmospheres comprising NH3 and NH3 - N2 - by a change of the atmosphere flow rate. The time needed to reach a stabilized state, after the initiation of a change in the atmosphere gas mix can be assessed relatively easily. The problem is much more complex if we want to predict the time of reaching a new stabilized state following a change in atmosphere flow rate. The time of reaching stabilized state is, in this case, a complex function of the flow rate of the atmosphere which forces the potential change, and of temperature. This problem, in the case of the NH3 type atmosphere, is the subject of investigation in this work. Factors are discussed, affecting the rate at which stabilized state is reached by the system after the introduction of a disturbance, necessary to attain the required nitriding potential.
关键词:nitriding processes; nitriding potential; NH3 atmosphere characteristics; stabilized stat;
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