Research On Property And Micro-Structure Of Laser Cladding WC-NI Layers On Steel

Laser cladding is the effective method to produce the layer with different andimproved structure and property compared to substrate using the laser as the source ofenergy. And it has many strong points, such as the fine structure, the uniformity chemistrycompose, the good property of the layer and the smaller thermal impact of the substrateand so on.Almost all the metal materials used in industry and life can be treated as thesubstrate of laser cladding technology. And there are many kinds of materials can be usedto produce laser cladding layer, including the Steel, Nickel and Cobalt alloy powder, andthe ceramic and pure metal. With the improvement on the technics of lap and the avoid ofcrack, the application of the laser cladding will expand widely.It is found that the layer can be metallurgically bonded to the substrate and thestructure of the layers are almost the same if they have the same substrate and alloy powderafter the SEM、EDS and XRD analysis. And the analysis of the reason and avoid method ofdisfigurement of the layer will be helpful to optimize the cladding layer.The result of microhardness test was measured and it can be seen that themicrohardness increased very rapidly from the substrate, and the microhardness in theentire cladding layer was equality. The incompletely dissolved WC particles in WC-Nicoatings increased the microhardness of the coatings. Besides it, the solid solutionstrengthening, dispersion hardening and microstructural refinement also contribute to theimprovement of the microhardness. And it is found that the microhardness of the layer thatscanned twice dropped than that just scanned once.The wear resistant of the laser cladding layers and thermal spray coating arereduced about90%and70%than the substrate. Weight loss of WC-Ni laser cladding layerwas reduced as the WC content increased from15%to30%and the wear resistant of thelaser cladding layer was better than the thermay sprayed coating. The powder deliver methods at present on laser cladding is limited on workrepair that need easier operation and the smaller surface for treatment. So it is valuable todevelop a new method deliver powder, and the crack and porous free coatings werefabricated by preplace powder of Ni-based nano-WC/Co composite coatings directly. It istestified 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 thebond between the layer and the mould, judge the feasibility to repair by laser cladding. Andit is found that the application on the dimension repair of mould is available, while it canbe remove or cover the crack on the surface but may not effective to treat the crack thatexist deep. And it is also tried the surface improvement on safe module of elevator andproduced the layer with good property, which proved the available of surface treatment onwork with this technology and it is need the deeper research to use it in industry.