The mechanical properties of medium carbon steel processed by a biomimetic laser technique

We investigate the effects of biomimetic laser surface treatment on the mechanical properties of medium carbon steel. Steel surface was strengthened by laser-treated or -hardened area (the biomimetic strengthening spots). Microhardness, UTS and YS are simultaneously improved by the martensitic microstructure with nano-sized carbides due to the self-quenching effect of laser treatment. The ductility is also increased but not continuously. This is because the laser-induced martensite is detrimental to ductility. In addition, thermal fatigue behavior of medium carbon steel is improved. Fewer cracks are found after thermal fatigue test. Crack nucleation and propagation are hampered by the strengthening spots. The biomimetic sample, as compared with the as-received counterpart, has a slower crack growth.