Influence of laser parameters on graphite morphology in the bonding zone and process optimization in gray cast iron laser cladding

The surface modification of gray cast iron through laser cladding produces a high-performance surface with low-cost materials, thereby reducing the manufacturing cost. This approach may considerably alter the phases in the bonding zone. In turn, the morphology of the graphite and adjacent phases influence the reliability and surface performance of the cladding layer. To optimize this process, this study performed numerical analysis and cladding experiments to analyze the carbon atom diffusion in graphite and examine the effects of scanning speed and laser power on graphite environment temperature, structural transformation, and graphite morphology in the bonding zone. The results showed that, in the case of constant laser power, as the scanning speed decreased, the diffusion of carbon atoms increased and became highly refined, thereby inhibiting poor graphite morphology and reducing micro-crack generation. At a constant scanning speed, the laser power slightly influenced the structure and macro-morphology of graphite. Considering the macro-morphology in the cladding layer and the micro-cracks in the bonding zone into consideration, we proposed that a laser power of 350 W and a scanning speed of 300 mm/min are the optimal process parameters.