铁基合金激光熔覆层裂纹控制的组织设计

Microstructure Design of Controlling Crack of Fe-based Laser Cladding Layer

通过对激光熔覆铁基合金进行组织设计和试验,获得了无裂纹、平均硬度为850.3HV(65HRC)的熔覆涂层。利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD)对熔覆层进行显微组织、相结构分析,结果表明:熔覆层为枝/胞晶凝固组织形态,熔覆层内弥散分布大量的颗粒相;残余奥氏体沿着枝/胞晶间分布,晶间的碳化物呈颗粒状弥散分布在晶间残余奥氏体上。摩擦测试结果表明,熔覆层的磨损形式主要为磨粒磨损,对比材料冷轧辊用钢9Cr2Mo磨损形式为磨粒磨损、粘着磨损和疲劳剥落。熔覆层的拉伸断口形貌为准解理和韧窝,并有沿晶粒边界形成的韧带,表明晶界残余奥氏体提高了熔覆层的韧性。

A Fe-based cladding layer which is free of crack and has average hardness 850.3 HV（65HRC） was obtained by microstructure design and laser cladding.The examinations of optic microscope（OM）,scanning electron microscope（SEM）,transmission electron microscope（TEM） and X-ray diffraction（XRD） showed that the microstructure of cellular and dendrite grains was observed in cladding layer,and a large number of granular particle reinforced phases dispersively distributed in the cellular and dendrite grain.Moreover,the bulk retained austenite and carbides distributed along the grain boundary were observed.The actual friction measurements also indicate that abrasive wear is the main mechanism for cladding layer,and the surface of cold roll steel 9Cr2Mo are abrasive wear,adhesive wear and fatigue breaking-off.The analysis of the tensile fracture surfaces reveal that laser cladding layers exhibit a mixture fracture mode of quasi-cleavage and dimple,and ductile belt along the grain boundary were observed,which is the evidence that toughness is improved by grain refinement.