Influence of nano-Al2O3 particles on the microstructure and wear resistance of the nickel-based alloy coating deposited by plasma transferred arc overlay welding

Nickel-based alloys powders with and without nano-Al2O3 (α-Al2O3) addition (Al2O3-free and Al2O3-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 Al2O3-free coating where consists of γ (Ni, Fe), (Fe, Cr)7C3, and (Fe, Cr)2B phases. Adding 0.8 wt.% nano-Al2O3 particles does not change the hypoeutectic microstructure characteristics of the Al2O3-free coating, though refines its microstructure and decreases its component segregation. The nano-Al2O3 particles being mainly tetragonal lattice (γ-Al2O3) which is different to that the added α-Al2O3 particles being rhombohedral lattice exist in the Al2O3-added coating. Adding nano-Al2O3 particles increases the mass fraction of the (Fe, Cr)2B phase and decreases that of the (Fe, Cr)7C3 phase, though such adding has little effect on the mass fraction of the total (Fe, Cr)-rich phases. The substructure of the Al2O3-free coating is mainly dislocations. Adding nano-Al2O3 particles promotes to form stacking faults and dislocation cell wall. The sliding wear resistance of the Al2O3-added coating is higher than that of the Al2O3-free coating.