7N01铝合金激光熔覆Al7075-SiC复合涂层组织及腐蚀性能

Microstructure and Corrosion Property of Laser Cladding Al7075-SiC Composite Coating on 7N01 Aluminum Alloy

高速列车用铝合金材料使用中存在腐蚀破坏的问题。为了改善铝合金的耐腐蚀性能,通过激光熔覆技术在高速列车用7N01铝合金表面制备耐腐蚀的Al7075-SiC金属基复合涂层。采用扫描电镜、X射线衍射对熔覆层进行了分析;对熔覆层的显微硬度进行测试。测试了熔覆层的极化曲线。结果表明:熔覆层由α-Al树枝晶和Al-Si共晶组成,熔覆层有Al4C3生成。熔覆层中未熔化的碳化硅硬质颗粒聚集于熔覆层底部。熔覆层硬度相对基体有所提高,但热影响区存在软化现象。熔覆层的极化曲线出现了钝化平台,熔覆层的耐腐蚀性优于基体材料的。由腐蚀形貌推测,腐蚀优先在Si C颗粒边界发生,保留了网状组织。

The problem of corrosion damage exists in aluminum alloy material during its use for high-speed train.In order to improve the corrosion resistance of aluminum alloy,the corrosion resistant Al7075-SiC metal matrix composite coating was prepared on the surface of 7N01 aluminum alloy for high-speed train by laser cladding technology.The cladding layer was studied by scanning electron microscope and X-ray diffraction analysis,and the hardness of the cladding layer was tested.The polarization curves of the cladding layer was tested.The results show that the cladding layer is composed ofα-Al dendrite and Al-Si eutectic,Al4C3 forms in the cladding layer.The unmelt SiC particles in the cladding layer aggregate at the bottom of the cladding layer.The hardness of the cladding layer improves compared with that of the substrate,but there is softening phenomenon at the heat affected zone.The polarization curves of the cladding layer shows a passivation platform,and the corrosion resistance of the cladding layer is better than that of the substrate material.By the corrosion morphology,it is assumed that the corrosion occurs preferentially at the boundaries of the SiC particles and the network structure is retained.