Überwachung und Regelung von Nitrier- und Nitrocarburieratmosphären mit dem HydroNit-Sensor

Abstract

In many technical processes the value of the hydrogen content of a gaseous atmosphere is a suitable feature for the characterization of a reaction within the atmosphere. This is for instance the case in gas nitriding and gas nitrocarburizing. If during these heat treatment processes the hydrogen content is measured, and the amount of other gas volumes fed into the heat treatment installation is known, so-called atmosphere potentials can be calculated on the basis of the ammonium dissociation and the watergas equilibrium normally established. The value of these atmosphere potentials gives information about the nitriding or nitriding and carburizing ability of the atmosphere. This paper presents a newly developed sensor for in-situ measurement of the hydrogen partial pressure, which enables the monitoring and control of the atmosphere avoiding the known disadvantages of analysers and solid electrolyte gas sensors. The procedure of calculating the atmosphere composition during nitrocarburizing conditions, based on the measurement of the hydrogen partial pressure and the calculation of atmosphere potentials, is shown. Finally, the measurement principle as well as measurements showing the response and measuring accuracy are presented.