ABSTRACT
Laser cladding is the effective method to produce the layer with different and improved structure and property compared to substrate using the laser as the source of energy. And it has many strong points, such as the fine structure, the uniformity chemistry compose, the good property of the layer and the smaller thermal impact of the substrate and so on.
Almost all the metal materials used in industry and life can be treated as the substrate of laser cladding technology. And there are many kinds of materials can be used to produce laser cladding layer, including the Steel, Nickel and Cobalt alloy powder, and the ceramic and pure metal. With the improvement on the technics of lap and the avoid of crack, the application of the laser cladding will expand widely.
It is found that the layer can be metallurgically bonded to the substrate and the structure of the layers are almost the same if they have the same substrate and alloy powder after the SEM、EDS and XRD analysis. And the analysis of the reason and avoid method of disfigurement of the layer will be helpful to optimize the cladding layer.
The result of microhardness test was measured and it can be seen that the microhardness increased very rapidly from the substrate, and the microhardness in the entire cladding layer was equality. The incompletely dissolved WC particles in WC-Ni coatings increased the microhardness of the coatings. Besides it, the solid solution strengthening, dispersion hardening and microstructural refinement also contribute to the improvement of the microhardness. And it is found that the microhardness of the layer that scanned twice dropped than that just scanned once.
The wear resistant of the laser cladding layers and thermal spray coating are reduced about 90% and 70% than the substrate. Weight loss of WC-Ni laser cladding layer was reduced as the WC content increased from 15% to 30% and the wear resistant of the laser cladding layer was better than the thermay sprayed coating.
The powder deliver methods at present on laser cladding is limited on work repair that need easier operation and the smaller surface for treatment. So it is valuable to develop a new method deliver powder, and the crack and porous free coatings were fabricated by preplace powder of Ni-based nano-WC/Co composite coatings directly. It is testified in the work that the new measurement is available to fabricate laser clad layers.It is tried to repair the mould to observe the improvement of the property and the bond between the layer and the mould, judge the feasibility to repair by laser cladding. And it is found that the application on the dimension repair of mould is available, while it can be remove or cover the crack on the surface but may not effective to treat the crack that exist deep. And it is also tried the surface improvement on safe module of elevator and produced the layer with good property, which proved the available of surface treatment on work with this technology and it is need the deeper research to use it in industry.
KEY WORDS： Laser cladding, Microstructure, Property, Nickel, Application
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