Effect of microstructure on the corrosion resistance of coatings by extreme high speed laser cladding

The corrosion resistance of 431 stainless coatings produced by a novel surface modification technology (EHLA) was analyzed. As the cladding speed increased, the dendrites became more refined and the composition distribution was more uniform. Corrosion tests showed that better corrosion resistance was achieved with a higher cladding speed. The uniform distribution of dendrite sizes and composition helped to improve the coating corrosion resistance. Many dislocations and stacking faults were found in the coatings prepared under 100 m/min cladding speed, which was beneficial for the nucleation of the passive film. The overlapping regions were weaker toward corrosion as the dendrites became coarser. Pitting mainly initiated at the junction of dendrites and inter-dendritic regions. High cladding speeds lead to refined dendrites and uniform distribution of composition which were helpful for the improvement of the coating corrosion resistance.