The Research Of Technology Of Laser Cladding And Tribological Behaviors Of Laser Coating On Aluminum Bronze

Main characteristic of Surface modification technique is improving surface performances of materials without altering the property of the substrate metal. The appearance of laser cladding technique enriching the field, offering a new way to improve the surface performances, and becoming an important part of the materials science. Some laser techniques, which including laser phase transformation techniques, laser cladding techniques and so on, not only have been widely applied in Fe-based materials but also begin to be used in the no-ferrous metals. In the paper, a Ni alloy layer was deposited on the QA19-4 aluminum bronze by laser cladding to improve its wear resistance. Through analyze the morphologic, microstructures and friction performances of laser coating, the influent factor of technology parameters on laser coating is summed.Both of different component alloy powder were confected accurately and mixed. Next, the alloy powder were weighed according to 0.02g～0.08g/mm². Then, the alloy powder were pre-parked on the QA19-4 aluminum bronze surface with emplastic, The pre-parked coating was compacted by hydraulic pressure after the vacuum desiccation (60～70℃). The laser scans pre-parked coating with decreasing laser power, which power begin at 3800～4000W, and decrease with 20～40W/s till the power is about 1900 W. The whole process use multi-scans whose overlap is 50% under argon condition, which current flux is 6L/s.The scan velocity is 6mm/s. Finally, the laser coating is uniform, compact and good metallurgic combined, the thickness of laser coating is 0.5～2mm and the hardness is 400～500 HV_0.2.Through analyze the morphologic, microstructures of laser coating, the results show that laser parameters have a great influent on laser coating. The lower power and more rapid scan velocity of laser can melt the alloy powder without melting QA19-4 aluminum bronze. The microstructure of cladding is affected by solidification rate. The microstructure of the cladding's surface is cellulated crystal. In the middle part of the cladding, the microstructure is dendritic crystal. Because of chilling effect of substrate QA19-4 aluminum bronze, the microstructure of the composite region upper is fine grain band. From the bottom to top of laser coating, chromic phase in laser coating have a transformation from dispersion to reticulum.Through analyze friction performances of laser coating, the results show that friction performances of laser coating is superior to that of QA19-4 aluminum bronze. Under dry friction condition, the major wear mechanism of laser coating are abrasive wear and flake strengthen phase, which wear volume is one third of QA19-4 material's. Under lubrication condition, the major wear mechanism is abrasive wear. With the increasing of wear speed, the surface of laser coating begin to arise adhesion. The wear volume and friction factor of laser coating lower than that of QA19-4 aluminum bronze. Therefore, the laser cladding can improve the friction performance of QA19-4 aluminum bronze.