【摘要】 采用定量金相法，提取激光熔覆Ｃｏ基合金熔覆层不同部位的枝晶组织特征（枝晶二次臂间距ＤｅｎｄｒｉｔｅＳｅｃｏｎｄＡｒｍＳｐａｃｉｎｇ），结果表明：随着离熔覆层与基材结合界面距离的增加，熔覆层枝晶特征尺寸随之减小，即组织不均匀；同一高度下不同部位的特征尺寸变化不明显，即组织均匀。采用激光熔覆解析模型，计算了熔池局部凝固特性参数（温度梯度Ｇ、界面推移速度ＶＳ和冷却速率Ｔ．），结合凝固理论，解释了激光熔覆层组织形成原因。建立了熔覆层组织不均匀性评判标准，依据标准对熔覆层组织进行评判，并在此基础上提出消除组织不均匀性的方法。更多还原

【Abstract】 A hypoeutectic Stellite 6 alloy, which is characterized by excellent wear and erosion resistance, has been extensively applied in industry. Laser cladding experiments with a hypoeutetic Stellite 6 alloy have been performed. The microstructure in the clad is a typical dendritic. The measured results of secondary dendrite arm spacing(SDAS) show that SDAS decreases as the distance of the target from the substrate increases. Furthermore, for a given targetsubstrate distance, the SDAS is uniform throughout the layer. The evolution of SDAS is discussed using the local solidification characteristic parameters(temperature gradient, interface moving speed, and cooling rate) deduced from an analytical model. A criterion of the microstructural heterogeneity is developed and shown to agree with the experimental results. Based on it, some methods for reducing the microstructural heterogeneity, are offered.更多还原