| In recent years, the NiAl intermetallic compound has attracted considerable attention due to its potential for high temperature protective coating application, attributing to its low density, high melting temperature, high thermal conductivity, and good oxidation resistance. Therefore, many researchers have tried to use the NiAl intermetallic compound as protective coating material, and the adopted techniques mainly include physical vapour deposition, direct current magnetron sputtering, and thermal spraying, etc. However, due to its own technical conditions, the adhesive ability between the coating and substrate is poor, thus restricted its engineering application at some extent.In contrast, laser cladding, as an advanced surface modification technique, is possible to generate NiAl alloy coating with low dilution, high density and with almost zero porosity content and strong metallurgical bonding between coating and substrate, which can effectively display the performance advantage of the NiAl intermetallic compound.In the present study, NiAl alloy coatings with different content of Y and Fe were prepared by laser cladding on the surface of 45# medium steel, respectively. The influence of Y and Fe on the microstructure and properties of the NiAl alloy coatings were systimetically investigated. Beside, NiAlBSi alloy coatings obtained at different scanning velocities were also researched in this paper. The microstructure and properties of the coatings were investigated using X-ray diffraction, scanning electron microscopy, electron probe micro-analyzer, Vickers hardness tester, friction wear testing machine, and thermal analyzer.The NiAl alloy coatings with different Y additions are mainly composed of NiAl dendrites, and the dendrites become gradually fine with increasing the Y addition. Y purifying action can effectively prevent the formation of Al2O3 oxide. However, when the Y addition is beyond 1.5at.%, the extra Y will react with O to form Y2O3 oxide, even participant alloying to form Al5Y3O12 oxide depending on the amount of Y added. The Y addition in a range of 1.5-3.5at.% reduces the hardness and anti-attrition of the NiAl clad layer, but improves obviously wear and high temperature oxidation resistances. The NiAlFe alloy coatings with different Fe contents are all composed of NiAl dendrites, and the dendrites become gradually fine with increasing the Fe content due to the increase of the composition under-cooling. With increasing of the Fe content, the high temperature oxidation resistances of the coatings decrease gradually due to the poor adhesion between the rich Fe oxide film and the substrate, while the hardness and the wear resistance present the trend of first increase then decrease, and reach the highest values at the Fe content of 10at.%, respectively. NiAlBSi alloy coatings obtained at different scanning velocities are all composed of NiAl dendrites. With increasing of scanning velocity, the hardness values of the coatings increase gradually due to refinement of the dendrites, while the wear resistance and the high temperature oxidation resistance present the trend of first increase then decrease, and reach the highest values at the scanning velocity of 4mm/s, respectively.
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