In Situ Oxidation of Steels as an Effective and Economical Pretreatment for Uniform and Consistent Vacuum Gas Nitriding Results

Author: Trevor Jones, Principal Engineer, Solar Atmospheres

Originally Published: October 2013

A vacuum-purge gas nitriding furnace was modified to develop a process and a furnace enhancement to produce a controlled in situ oxide layer on the surfaces of steel parts using various oxidation techniques. The process is an effective alternative to conventional grit blasting of materials as a means of surface preparation for uniform and consistent nitriding results. Pre-oxidation is known to enhance receptivity of steel part surfaces to the effects of nitriding, and in situ oxidation is inherently efficient and economical. Topics discussed include the type of oxidizing carrier used in the furnace, practical methods used to control the oxidation, and a gas delivery system developed to inject gases with an elevated dew point for the purpose of providing a controlled oxidizing atmosphere. Comparative tests with other activation techniques, and results with no activation, will be discussed along with approaches to technical process difficulties encountered.

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