A. Malas, BOC Gases UK, Sheffield, United Kingdom; P. F. Stratton, BOC, Huddersfield, United Kingdom

Summary: There are generally two types of surface change commonly encountered when metals are heated in furnaces. One is oxidation/reduction; the second one is carburisation/decarburisation that relates to the reaction of the gases with the metal surface in such a way as to add carbon to the surface of low-carbon steel or to remove carbon from the surface of high-carbon steel. The latter is known as decarburisation. Decarburisation may also be commonly described as loss of carbon from the surface of ferrous materials. It is generally an undesirable material characteristic in the manufacturing industry. When components are hardened, decarburisation will reduce the surface hardness of the material and hence decrease its operational life under conditions of wear. This unwanted condition must therefore be eliminated from the heat treatment process. This paper summarises the causes of decarburisation in heat treatment and gives some troubleshooting tips for industrial practice, together with a case study.