宽带激光熔覆铁基非晶涂层的微观组织及形成机制

Microstructures and Formation Mechanism of Fe-Based Amorphous Coatings by Broad-Band Laser Cladding

采用宽带激光熔覆技术,在304L不锈钢表面制备了Fe-Cr-Si-P非晶涂层,分析了涂层的组织结构及形成机制,建立了激光熔覆物理和数学模型,得到了熔池沿深度方向的温度梯度及冷却速率的变化规律。结果表明,涂层微观组织的界面区是平面晶和外延生长树枝晶,中部区域为非晶区,表面为梅花状树枝晶区。凝固过程中,从熔池底部到表面的温度梯度逐渐减小,冷却速率逐渐增大。结合凝固理论,建立了涂层组织特征与形状控制因子及冷却速率的关系模型。

The Fe-Cr-Si-P amorphous coatings are prepared on the 304L stainless steel surface by using the broad- band laser cladding technique. The microstructures and formation mechanism of these coatings are analyzed. The mathematical and physics models of laser cladding are established, and the change rules of temperature gradient and cooling rate of molten pool along the depth direction are obtained. The results show that the microstructures of the coating are planar crystalline and epitaxial growth dendrites in the bonding zone, amorphous character in the middle zone and fine equiaxed crystalline on the surface. During the solidification process, the temperature gradient from the bottom to the surface for the molten pool decreases and the cooling rate increases gradually. Based on the rapid solidification theory, the model of the relationship between the coating microstructure character and the shape control factor as well as that between the coating microstructure character and the coolimz rate is established.