Laser cladding of wear resistant Cu-base coatings on cast Al-Si alloys

Abstract

Laser cladded Mn-Al bronze coatings on AA333 cast alloy substrate primarily for possible automotive applications were successfully produced using a 6 kW continuous wave CO2 laser with an oscillating beam for various processing conditions. The experimental test matrix included a 3x3 matrix of the three major laser process parameters—laser power, traverse speed, and powder feed. The produced coatings were dense, well-bonded, free of cracks, and relatively much harder (up to 400 kgf/mm2) with sufficient toughness characteristics. Preliminary evaluation of the select coating microstructures using optical (OM) and scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS) and x-ray diffractometry (XRD) revealed columnar type grains of varying sizes, homogeneous distribution of the alloying elements Cu, Mn, Al (major), Fe, and Ni (minor), and face-centered-cubic (fcc) Cu-based solid solution with enhanced lattice parameter, depending on the as-cladded alloy composition and process parameters. The coating/substrate interface microstructures were found to contain α-Al (fcc) and θ-CuAl2 (tetragonal). The dry sliding tribological tests revealed encouraging results of significantly better properties of the coatings: down to 1/3 of the wear rate of the AA333 substrate, and much less prone to full seizure under identical test conditions of 10 lbs normal load at 600 rpm, 30.3 mm radius of sliding. Some of the possible wear mechanisms of coating and substrate are explained, and important aspects of coating characteristics as a function of laser cladding parameters are also discussed.Laser cladded Mn-Al bronze coatings on AA333 cast alloy substrate primarily for possible automotive applications were successfully produced using a 6 kW continuous wave CO2 laser with an oscillating beam for various processing conditions. The experimental test matrix included a 3x3 matrix of the three major laser process parameters—laser power, traverse speed, and powder feed. The produced coatings were dense, well-bonded, free of cracks, and relatively much harder (up to 400 kgf/mm2) with sufficient toughness characteristics. Preliminary evaluation of the select coating microstructures using optical (OM) and scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS) and x-ray diffractometry (XRD) revealed columnar type grains of varying sizes, homogeneous distribution of the alloying elements Cu, Mn, Al (major), Fe, and Ni (minor), and face-centered-cubic (fcc) Cu-based solid solution with enhanced lattice parameter, depending on the as-cladded alloy composition and process parameters...