Surface alloying of AISI 1045 steel in a nitrogen environment using a gas tungsten arc process

The effects of varying the addition of nitrogen to the shielding gas during GTA (gas tungsten arc) surface alloying of an AISI 1045 steel substrate with a preplaced layer of ferrotitanium (FeTi) powder were investigated. The penetration and cross-sectional area of the alloyed layers increased with the nitrogen content in the shielding gas. Different nitrogen contents in the shielding gas also caused the formation of two main microstructures: (1) TiN dendrites distributed in a ferrite(α)–Fe3C matrix at a high nitrogen content and (2) Ti(CxNy) in a matrix of ferrite(α) and eutectic structure of ferrite(α) and Fe2Ti at a low nitrogen content. Specimen melted under pure argon (0 vol% N2) was comprised of TiC in a matrix of ferrite(α) and eutectic structure of ferrite(α) and Fe2Ti. The latter also showed the highest hardness, which could be attributed to the presence of the fine eutectic structure and low dilution of the layer.