In situ surface hardening during turning via pyrolytic carburization

This paper describes the application of a carbonaceous feed gas (acetylene with a nitrogen shield) in a turning operation to achieve in situ surface hardening of AISI 1018 steel. Preliminary results suggest that the tool–chip interface temperature provides sufficient energy to decompose the feed gas. This enables carbon diffusion into the work surface which, in effect, carburizes the surface and increases the hardness during the turning operation. It is proposed that this approach may enable the machining of low hardness materials, while simultaneously providing increased surface hardness for the machined product. This could result in the reduction/elimination of post-machining heat treatment and could, therefore, have significant implications for the die/mold manufacturing community.

► A carbonaceous feed gas (acetylene with a nitrogen shield) was used in an interrupted turning operation to achieve in situ surface hardening of AISI 1018 steel.
► Using the tool–chip interface heat to decompose the feed gas, it is proposed that carbon was diffused into the work surface and, subsequently, the hardness increased during the turning operation.
► It is proposed that this approach may enable the machining of low hardness materials, while simultaneously providing increased surface hardness for the machined product.