Abstract
Nickel-based alloys powders with and without nano-Al 2O 3 (α-Al 2O 3) addition (Al 2O 3-free and Al 2O 3-added, respectively) were deposited on Q235A low carbon steel using plasma transferred arc (PTA) welding machine. Microstructures of the two deposited coatings were studied by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). More details about the phase compositions and their mass fractions in the deposited coatings were obtained with applying the Rietveld refinement method to analyze XRD patterns. Wear resistance experiment was conducted on one sliding wear machine to value the deposited coatings. The results show that the typical hypoeutectic microstructure and the component segregation exist in the Al 2O 3-free coating where consists of γ (Ni, Fe), (Fe, Cr) 7C 3, and (Fe, Cr) 2B phases. Adding 0.8 wt.% nano-Al 2O 3 particles does not change the hypoeutectic microstructure characteristics of the Al 2O 3-free coating, though refines its microstructure and decreases its component segregation. The nano-Al 2O 3 particles being mainly tetragonal lattice (γ-Al 2O 3) which is different to that the added α-Al 2O 3 particles being rhombohedral lattice exist in the Al 2O 3-added coating. Adding nano-Al 2O 3 particles increases the mass fraction of the (Fe, Cr) 2B phase and decreases that of the (Fe, Cr) 7C 3 phase, though such adding has little effect on the mass fraction of the total (Fe, Cr)-rich phases. The substructure of the Al 2O 3-free coating is mainly dislocations. Adding nano-Al 2O 3 particles promotes to form stacking faults and dislocation cell wall. The sliding wear resistance of the Al 2O 3-added coating is higher than that of the Al 2O 3-free coating.
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