Investigation of laser cladding ceramic-metal composite coatings: processing modes and mechanisms

The motion of ceramic particles in laser cladding ceramic-metal composites (LCCCs) is a very important factor which affects not only the distribution of the ceramic particles in the LCCCs but also the minimum specific energy needed to form LCCCs, as well as the choice of laser processing parameters. In this paper, the motion rules of the ceramic particles in LCCCs have been investigated systemically by designing special experiments. The results demonstrate that there are two typical motion modes of ceramic particles during the formation of LCCCs: one mode is defined as the stirred mode, in which the ceramic particles move along with the liquid matrix alloy in the laser melting pool; the other mode is defined as the sintered mode, in which the ceramic particles do not move apparently, while the liquid matrix alloy infiltrates along the surface of the ceramic particles to the bottom, so forming the LCCCs. The minimum specific energy needed for LCCCs with the stirred mode is much less than that with the sintered mode. As far as a certain combination of the ceramic particles and the matrix alloys is concerned, the motion modes of the ceramic particles in LCCCs depend not only on the composition of the matrix alloys and their physical and chemical properties, but also on the kind, size, shape and the weight per cent of the ceramic particles. Thermodynamic analyses are described qualitatively which can explain these results very well.