为提高碳钢的耐腐蚀性能,利用高功率连续半导体激光器分别以6和12 mm/s的熔覆速度,在E235低碳钢基体上成功制备了哈氏合金涂层.利用稀硝酸溶液溶去E235钢基体后,获得激光熔覆层与钢基体之间的界面,并对该界面的显微组织、化学组分以及力学性能进行系统研究.研究发现在涂层/基体界面上的晶界处,存在着一种特殊"边缘",而这种特殊"边缘"由真实晶界与发生晶界腐蚀后留下的腐蚀痕迹所组成.界面主要呈现出由激光熔覆后迅速冷却和Ni元素向界面扩散而导致的奥氏体组织.另外,以12 mm/s的激光熔覆速度制备的涂层及其界面比6 mm/s情况下制备的涂层及其界面具有更高的硬度,而涂层/基体界面上的晶界与对应的晶粒相比具有更高的摩擦因数.同时,激光熔覆速度越快,界面上的晶粒尺寸越细小,界面处Ni和Fe的扩散速度越低,摩擦学性能越优异.
In order to improve the corrosion resistance of carbon steel, Hastelloy coatings were prepared on E235 steel substrate by a high power diode laser with laser scanning speeds of 6 and 12 mm/s, respectively. The interface between the coating and substrate was firstly exposed by dissolving off the substrate. Its microstructure, composition and mechanical properties were systemically studied. Special "edges" along the grain boundary were found at coating/substrate interface. These "edges" consisted of intergranular corrosion area and real grain boundary. The interface of coating mainly displayed austenite structure ascribed to the rapid solidification as well as the dilution of Ni during preparation. Additionally, Hastelloy coating and its interface prepared at the speed of 12 mm/s showed higher hardness than that prepared at the speed of 6 mm/s. Grain boundaries had higher friction coefficient than grains at both coating/substrate interfaces. Moreover, the interface at higher laser scanning speed exhibited smaller grains, lower dilution rates of Ni and Fe as well as a better tribological property.
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