Surface carbon enrichment of stainless steel using nanosecond pulsed laser surface alloying of a graphite based coating

Laser surface alloying is a promising technique for modifying and/or improving surface properties of forming tools used in the fabrication of thermoplastic composite parts. The results of a study on laser surface alloying of graphite based coatings on ferritic stainless steel using a nanosecond pulsed laser source is presented. The effect of different laser processing parameters and coating types on the laser-induced carbon diffusion in the steel are analyzed. The morphology of the processed areas was characterized using confocal microscopy and scanning electron microscopy. The atomic concentration of diffused carbon was determined using energy-dispersive X-ray spectroscopy. It was found that the surface carbon content of stainless steel can be increased substantially up to 70% in weight. Cross-sectional analysis revealed the dependence of diffusion thickness on the accumulated laser fluence, having a maximum depth of about 6.5 µm. In comparison to low and high carbon steel, and unprocessed stainless steel, laser processed samples demonstrated improved wear properties.