Formation and crystallization of amorphous structure in the laser-cladding plasma-sprayed coating of Al-Si alloy

An Al-Si alloy surface was plasma sprayed with a Ni-Cr-B-Si coating. This coating was remelted by a 5kW CO2 laser, and the resulting microstructure was characterized by both scanning and transmission electron microscopy. Both crystalline and amorphous structures were observed to coexist in the remelted layer. Heat resulting from laser scanning precipitated some Ni3Al in the amorphous region. A distribution in Ni3Al precipitate size, from nanometer to submicrometer, was observed. Microhardness in the amorphous region measured to HV 1235, which is four times as hard as the untreated plasma-sprayed zone.