Influence of process parameters on the cracking rate and morphology of the laser melting and quenching zone in vermicular graphite cast iron

Laser melting and quenching experiments were conducted on vermicular graphite cast iron by employing 3 kW solid fiber laser. The cracking rate in the quenching zone,the morphology of the melting zone,microhardness and microstructure were analyzed. The results show that,at a given flow rate of shielding gas,increasing the laser power or reducing the scanning speed could facilitate the reduction of cracking rate in the quench zone. When the laser power was constant,the optimum flow rate of the shielding gas changed with the scanning speed. With the increase of laser power,the morphology of the quenching zone extended to the substrate. The morphology extended vertically and horizontally in the melting zone,and then in other directions. After that,it extended vertically and horizontally, and cycled. The gross area of the melting zone increased consequently, and the morphology of the quenching zone changed from flat to calyptra.