Microstructure and mechanical properties of laser surface alloyed coatings prepared on cast Al–Si

Abstract

Laser surface alloyed (LSA) layers were obtained on cast Al–Si using a CO₂ continuous transverse flow laser beam with maximum power of 10 kW. The microstructure of the modified layers was examined using scanning electron microscopy and transmission electron microscopy. Surface alloying with Ni based powder generated a layer composed of γ-Ni(Cr,Fe), Ni₃ Al, T(Al,Fe,Si), CrB, and Cr₂₃ C₆. The matrix phase in the modified layer was γ-Ni(Cr,Fe), with strengthening phases present. Microhardness and wear resistance tests were also performed: the average microhardness is around 3·1 to 3·6 GPa, three times higher than in the substrate. The antiwear properties of the LSA modified layers were also greatly improved, with relative wear resistance approaching 10 to 12. Finally, the wear mechanisms of LSA modified layers were studied by surface morphology analysis.