Laser Sintering of Nano-Al₂O₃ Powders on Plasma Sprayed Ceramic Based Coatings

This paper describes an investigation of nano-Al₂O₃ powders reinforced ceramic coatings, which has included NiCrAl and Al₂O₃+13%wt.TiO₂ coats pre-produced by atmosphere plasma spraying, implemented by laser sintering. Commercial NiCrAl powders were plasma sprayed onto 45 Steel substrates to give a bond coat with thickness of ∼100μm. The 600μm thick Al₂O₃+13%wt.TiO₂ based coating was also plasma sprayed on top of the NiCrAl bond coat. With 2.5kw continuous wave CO₂ laser, nano-Al₂O₃ ceramic powders were laser sintered on the based Coatings. The micro structure and chemical composition of the modified Al₂O₃+13%wt.TiO₂ coatings were analyzed by such detection devices as scanning electronic microscope (SEM) and x-ray diffraction (XRD). Microhardness, wear resistance and corrosion resistance of the modified coatings were also tested and compared with that of the unmodified. The results show that the crystal grain size of Al₂O₃ had no obvious growth. In addition, due to the nanostructured Al₂O₃ ceramic phases, the coatings exhibited higher microhardness, better wear resistance and corrosion resistance than those unmodified counterparts. The complex process of plasma spraying with laser sintering as a potential effective way of the application of ceramic nano materials was also simply discussed and summarized in the end.