Investigation on in-situ laser cladding 5356 aluminum alloy coating on 5052 aluminum alloy substrate in water environment

In this paper, underwater dissimilar aluminum alloy laser cladding has been investigated for the first time through a laser nozzle. The influences of water environment on laser cladding of dissimilar aluminum alloy were researched under optimized process parameters. With the transfer of cladding environment from air to water, the height of cladding zone (CZ) and the cladding angle increased, but the width of CZ and the depth of melting zone (MZ) decreased. The microstructure of MZ and CZ were columnar dendrites and equiaxial dendrites, but the underwater microstructure was much smaller than that of the in-air. Both underwater and in-air CZ were composed of Aluminum phase and Al_0.5Fe₃Si_0.5 phase, while the formation of intermetallic compound increased in the in-air CZ. The water environment was beneficial to reduce the magnesium burning loss in the CZ. In the underwater CZ, although the decrease of hard phase compound (Al_0.5Fe₃Si_0.5) formation made microhardness value go down, the microhardness value went up with the increase of magnesium content and the refinement of microstructure. Finally, under the combined action of these three factors, the average microhardness value of underwater cladding layer was higher than that of the in-air cladding layer.