Effect of laser energy density on microstructural evolution and wear resistance of modified aluminum bronze coatings fabricated by laser cladding

Abstract

Modified aluminum bronze coating was successfully prepared using laser cladding. This research aimed to clarify the relationship between laser energy density and macrostructure, microstructure, microhardness and wear resistance of modified aluminum bronze coating. According to the experimental results it could be concluded that the reduction of laser energy density effectively improved the formability of the cladding layer surface, but low energy density could not fully melt powder. At the optimum laser energy density of 42.4 J/mm2, the cladding layer had the best combination of good flatness and density. There was no change in the composition phase categoryof samples prepared with varied laser energy densities, but the content of each phase varied. The aluminum bronze coating was mainly composed of α phase, κ phase, β’ phase. The content of α phase and κ phase reduced due to the decrease of laser energy density, and Widmanstatten side plate structure appeared in the case of low energy density. As the laser energy density decreased, the crystal grain size first decreased and then increased. An orthogonal scanning strategy leading to a random orientation of the aluminum bronze coating prepared by laser cladding shown as the EBSD pattern. The Schmidt factor and KAM increased with laser energy density decreased. Laser energy density played an important role in controlling the microhardness and wear resistance of coatings. Under the optimized process parameters, the maximum microhardness could reach 341.72 HV, and the minimum wear was only 4.37 × 10−2 mm3/N m.