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Microstructures And Properties Of Laser Cladding Al-Y-Ni Alloys Coatings On Al Alloys

Posted on:2008-01-01Degree:MasterType:Thesis
Country:ChinaCandidate:X J ChenFull Text:PDF
GTID:2121360272969020Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
The aluminium alloy has been widely used in the fields of automobile,spaceflight and transportation areas because of its high intensity,low density ,good forming quality and so on. But its low hardness and poor corrosion resistance limit its wide application. Laser cladding, a kind of case strengthening technique which has been developed for some twenty years, has some unique advantages compared with the common surface engineering processes. It's an effective technique to improve the hardness and corrosion resistance of aluminium alloys.In this paper, the Al-Y-Ni alloys coatings were prepared on Al-based alloy by laser cladding. From these work, we got many experiences about laser processing parameters, material's physical parameters and the powder preparing of laser cladding.The microstructure, phase, element distribution and microhardness have been analyzed with the aid of optical microscopy, X-ray diffraction, scanning electron microscope and microhardness-tester. It was shown that the coatings have smooth and continuous surface, and metallurgically bond to the substrate. The microstructures were typical extension growth on plane basis at the cladding layer bottom, cellular crystals near the bonding zone, dendrite crystal in the middle of the molten layer and equiaxed crystals at the top of the cladding layer. The laser power and scanning velocity are the most important influences of the microstructures. The elements were distributed as a parabola in the landscape orientation of cladding layers. There was much Al in the cladding layer surface and much more Y and Ni in the bottom of the cladding layer. The Al, AlNi, Al2Ni6Y3, Ni3Y and Y2Ni7 are the dominant phases in the cladding zone. These phases are governed by the laser processing parameters as well as the coating's chemical composition. The average hardness of cladding layers is about 80HV.The main problems and their improving methods of laser cladding Al-Y-Ni alloys coating on aluminium alloys were elucidated. And finally, the future work was put forward.
Keywords/Search Tags:laser cladding, Al, Al-Y-Ni alloys coatings, microstructures, phases, elements, hardness
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