Oxygen Probes for Controlling Nitriding and Nitrocarburising Atmospheres

Abstract

By analogy with carburising, electrochemical concentration cells with oxygen conducting solid electrolytes have proved their suitability for the control of oxynitriding atmospheres, both as oxygen probes and as nitriding probes using two cells. Their application to nitrocarburising atmospheres is currently under evaluation. The measurements and calculations described in the present paper make possible the development of computer aided control of gas nitriding atmospheres. Process control on the basis of probe signals provides a more precise and flexible approach to meeting the demands made on surface layers. It can prevent disturbances caused by uncontrolled oxygen intake andfacilitates a rational gas regime, thus contributing to process and product optimisation.

Progress in sensor controlled nitriding and nitrocarburising

“…In order to obtain the further parameter for the nitriding atmospheres, the measurement of oxygen partial pressure needs to be carried out in the measurement gas and in the same gas after complete decomposition of ammonia. For the measurement and control of gasoxinitriding the well tried sensor, the E-probe, 8 can not be applied for reaction gases with a high carbon potential. 28 Therefore in a QE probe* which has been recently developed and evaluated by the University of Greifswald and TU Bergakademie Freiberg, the measurement gas is totally decomposed at a temperature ,825uC.…”

“…8. The decomposition of the ammonia is essentially thermal in nature and occurs catalytically only slightly on the surface of workpiece.…”

Second Lakhtin memorial lecture

“…The use of a solid electrolyte probe for observing and controlling the nitriding process is described in detail in earlier works [7,8]. It has been mentioned that the partial pressure PH20/PH,_in a homogeneous reaction gas is closely connected with the reactions that occur in carburization.…”

“…It has been mentioned that the partial pressure PH20/PH,_in a homogeneous reaction gas is closely connected with the reactions that occur in carburization. Reliable probes are available for controlling and governing nitriding and gas nitrocarburizing with a low carbon potential [7,8]. It should be noted that the program for computing the composition of the atmosphere in controlled gas nitriding is based on the algorithm suggested by T. Bell and his coworkers in 1973 [9].…”