Laser surface treatments of iron-based substrates for automotive application

In the present work laser surface alloying of low carbon steel with carbon has been investigated for automotive application. The laser used was Nd-YAG, having a wavelength of 1.06 μm. It was operated at energy levels between 5 and 30 J, pulse duration from 1.5 to 4 ms and beam diameter varied between 1 and 3 mm. As a result of laser treatment at different energy levels and pulse durations, treated layers of varying thickness between 0.03 and 0.20 mm with carbon concentrations exceeding the eutectic point are produced. As a consequence of this treatment, a range of microstructures and microhardness values was obtained. High hardness values were observed in the layers with predominantly martensite structure (650 Hv) and relatively low values in region showing austenite microstructure (500 Hv) and maximum hardness (850 Hv) was found in the layer, which showed large proportion of Fe3C. Surface melting of nodular cast iron by ruby laser (0.69 μm wavelength) has been also reported. The presence of retained austenite and martensite was found to be a characteristic feature in most of the treated layers.