Elimination of the porosity in the laser clad region of aluminum alloys by laser remelting

In order to eliminate the porosity that often occurs in the molten zone after laser cladding, a new approach involving double laser processing has been investigated. In the process (consisting in laser cladding followed immediately by laser remelting), the porosity disappears to a great extent. The experimental results show that in the laser remelting large gas bubbles can float out of the molten pool surface and the remainder gases are dissolved in molten pool on heating. The dissolved gases, mainly hydrogen, are still reserved in the aluminum alloys and have no time to be released during rapid solidification as the much higher cooling rate. Better microhardness in the remelted zone of the aluminum alloys at both normal and elevated temperatures can be obtained. The process of laser cladding followed immediately by laser remelting can also remove macrosegregation in the clad zone. Homogeneous microstructures are obtained in the double laser process zone.