Study On Laser In-situ Cladding Tin/ZrN Composite Layer On Zirconium Alloy

The composite coating of Ti N/Zr N is manufactured on the surface of zirconium alloy by in situ laser cladding technology in order to improve wear resistance and corrosion resistance of zirconium alloys, which used as nuclear fuel cladding material on nuclear industry. The structure of the cladding layer is analyzed, which including the surface morphology, phase structure,microstructure, phase composition, micro-hardness, by using materials testing equipments, such as optical microscope(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD), microhardness tester and so on.And a preliminary study on the influence of process parameters of laser power, scanning speed, overlap rate of cladding on quality of cladding layer.The major works and conclusions are as follows:(1) The problems which easily occurs on the laser cladding technology by the way of direct preparation of ceramic phase is analyzed and summarized. Putting forward the method of manufacturing the composite coating by in situ laser cladding technology to enhance the bonding strength of ceramic phase stability and matrix, to reach the purpose of improving the quality of cladding layer.(2) By designing the laser cladding materials and optimization of laser parameters, the composite coating of laser cladding is fabricated on zirconium alloy substrate.The results show that, there is less holes and cracks in the whole cladding layer, which is good metallurgical bonding with the substrate. The surface of laser cladding layer is mainly composed of dendrites structure, the middle part of layers is composed of both dendritic and part of granulation tissue, the cladding layer at the bottom zone is formed of granulation tissue and fibrous tissue, the cladding layer is mainly composed of Zr, Zr N, Ti N phase composition.(3) By the study of the influences on the cladding layer quality, which created by the laser process parameters on the single track and large area scanning on the laser cladding, analyzing the situation of the cladding layer surface morphology changes. The results show that, with the increase of laser energy density, the surface morphology of cladding layer becomes better; By the way of overlapping laser scanning, the surface morphology of the cladding layer can be greatly improved and with the increase of overlapping rate, surface morphology of cladding layer is improved.