Laser control melting of alumina surfaces with presence of B4C particles

Laser gas assisted controlled melting of alumina tile surface is carried out in this work. A carbon coating containing 5% of B4C particles is formed at the tile surface prior to laser treatment process. The morphological and microstructural changes in the treated layer are examined using X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscope. The surface microhardness is measured and the residual stress formed at the surface vicinity is obtained from the X-ray diffractograms. It was found that microhardness of the surface increases significantly after the laser treatment process, which is attributed to high cooling rates and the formation of nitride species at the surface. The residual stress formed at the surface is compressive and no micro- or major-cracks are observed at the laser treated surface.

► Dense and fine grains are formed in the surface region and columnar structures are formed underneath.
► The presence of carbon film enables to form AlN, AlON, and Al(C, N) compounds at surface.
► Presence of B4C particles and nitride species increases surface microhardness notably.
► The residual stress formed at the surface is compressive.