Activation of carbon deposit in the process of vacuum carburizing with preliminary nitriding

A variety of vacuum carburizing methods with preliminary nitriding at the stage of heating the charge for carburizing aim at limiting primary austenite grain growth during the process. In such a case, carburizing may be conducted at temperatures even above 1000 degrees C. This article presents a study on the activation of carbon deposit (which was formed in the preceding processes of carburizing in the vacuum furnace chamber) under the influence of activation with hydrogen derived from ammonia dissociation. The optimum temperature range of ammonia addition to the furnace chamber was determined in order to avoid the activation of the deposit, thus also preventing the introduction of an additional, uncontrolled source of carbon atoms to the process. (C) 2012 Elsevier Ltd. All rights reserved.