Effect of nano-ZrO2 protective layer on the microstructure and surface property strengthening mechanism of underwater wet laser Fe-based cladding layer.

Underwater wet laser cladding technology has become one of the research hotspots in the marine engineering, but the existence of the water environment inevitably leads to process instability and defects. In this study, the nano-ZrO 2 protective layer was used to increase the viscosity of the molten pool surface to resist the impact force generated by the high-speed water jet, and the underwater wet laser Fe-based cladding layer with good forming quality and desirable performance was successfully prepared. The nano-ZrO 2 protective layer improved the formability of the cladding layer and guaranteed the depth of the melt pool, while reducing the depth of the heat affected zone. The addition of nano-ZrO 2 particles reduced the average grain size of the cladding layer from 4.90 μm to 3.66 μm. In addition,the corrosion resistance of the cladding layer was greatly improved with the application of the nano-ZrO 2 protective layer, with the evident passivation region of 0.74 V. The wear rate of the cladding layer with the nano-ZrO 2 protective layer (0.64×10-15m3N-1m-1) was significantly lower than that of the substrate (9.01×10-15m3N-1m-1), and the excellent wear resistance of the cladding layer with nano-ZrO 2 protective layer benefited from the good carrying capacities and high microhardness of the microstructure with ZrO 2 particles. This study reveals the strengthening mechanism of nano-ZrO 2 protective layer on the Fe-based cladding layer, which can provide theoretical guidance for the development of the underwater laser cladding. • The Fe-based cladding layer with good formability was successfully prepared underwater. • The protective mechanism of the nano-ZrO 2 protective layer is studied in detail. • The nano-ZrO 2 protective layer can refine grains and decline heat effect. • The corrosion and wear performances of Fe-based cladding layer were improved by nano-ZrO 2 protective layer. • The nano-ZrO 2 induced grain refinement enabled Fe-based cladding layer to be further wear resistant. [ABSTRACT FROM AUTHOR]