Localized boriding of low-carbon steel using a Nd:YAG laser

Localized boriding of low-carbon steel by the conventional technique requires tedious preboriding treatment and a long processing time. Laser boriding of low-carbon steel can be performed faster, and without any preboriding treatment. The feasibility of selective boriding of AISI 1018 steel using a NdYAG laser has been investigated. High hardness in the range 950–2200 H_v was obtained during laser boriding of AISI 1018 steel. The wide range of hardness is due to the variety of microstructures possible during laser boriding. Electron microprobe analysis showed that the highest hardness (2200 H_v) was due to the formation of FeB, and the lowest hardness was due to a mixture of Fe₂B and eutectic (_Fe+Fe₂B). The most desirable microstructure in laser boriding of AISI 1018 steel was found to be Fe₂B, which incorporates a combination of a high hardness, in the range of 1300–1700 H_v, and a compressive stress at the treated surface.