等离子离心熔覆制备钢管内壁梯度涂层

Gradient coating deposited on interior surface of a tube using plasma transferred arccentrifugal cladding

运用等离子离心熔覆技术在钢管内壁成功制备厚度约为2 mm铁基梯度涂层,采用该方法制备的涂层结构致密、无气孔和裂纹。采用扫描电镜、X射线衍射仪和电子探针对熔覆层的显微组织、物相、成分分布进行表征和分析;并对该梯度涂层的硬度分布和耐磨性能进行检测。结果表明:离心熔覆时熔池中的Fe、W、Mo元素在离心力作用下发生径向迁移而导致熔覆层形成梯度显微组织,沿熔覆层由里及表由亚共晶向共晶和过共晶过渡;大量碳化物(M23C6、M7C3和M6C)在表层的生成保证了该区域的硬度和耐磨性,梯度熔覆层表层的显微硬度为基体的7.5倍,熔覆层摩擦系数和磨损量分别为GCr15的88%和21%。

Iron based gradient coating was deposited on the interior surface of a tube using plasma transferred arc centrifugal cladding（ PTACC）. Microstructure,phase constitution and composition of the coating were characterized by means of OM,SEM,XRD and EPMA.Mechanical properties of the coating were investigated by Vickers micro-hardness test and abrasion test. The results show that the Fe,W and Mo elements take a rodial move under the effect of centrifugal force,which results in a graded microstructure in the coating. The microstructure ranges from hypoeutectic structure in the inner layer to hypereutectic structure in the outer layer with near eutectic structure as the intermediate layer. Because of the carbides（ M23C6,M7C3,M6C） embedded in the outer layer,hardness of the coating is 7. 5times of that of the substrate while wear coefficient and wear mass loss of the coating are 88% and 21% of that of GCr15 steel,respectively.