Ju Jiang, Zhou Yang, Kang Maodong, Wang Jun
Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Materials (Basel). 2018 Oct 22;11(10):2061. doi: 10.3390/ma11102061.
The mould foot roller is a key component of a continuous casting machine. In order to investigate the possibility of using laser cladding to repair mould foot roller, Fe-based powders and 42CrMo steel are used in this work. The laser cladding process parameters were optimized by orthogonal experiments. The chemical compositions, microstructure, properties of the cladding layer under the optimum process parameters, and substrate were systematically investigated by using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness test, wear test, and salt spray corrosion test. The results indicate that the primary factor affecting the width and depth of the cladding layer is laser power. The scanning speed also has a significant effect on the height of the cladding layer. The optimum process parameters for repairing the mould foot roller are 2 kW laser power, 4 mm/s scanning speed, and 15 g/min feeding rate of powder. Along the depth direction of the cladding layer, the microstructure of the coating gradually transforms from plane crystal, cell grains, or dendrites to equiaxed grains. The matrix is mainly martensite with retained austenite; the eutectic phase is composed of netlike M₂B, particulate M(C,B)₆, and M₇(C,B)₃ phase. The hardness of the cladding layer is significantly improved, about three times that of the substrate. The weight loss of the cladding layer is just half that of the substrate. Its wear resistance and corrosion resistance have been significantly improved. The work period of the laser cladding-repaired foot roller is much longer than for the surfacing welding-repaired one. In summary, laser cladding technology can increase the life of mould foot rollers.
结晶器足辊是连铸机的关键部件。为了研究采用激光熔覆修复结晶器足辊的可能性，本工作选用了铁基粉末和42CrMo钢。通过正交试验对激光熔覆工艺参数进行了优化。利用光学显微镜（OM）、扫描电子显微镜（SEM）、能谱仪（EDS）、X射线衍射仪（XRD）、显微硬度测试、磨损试验和盐雾腐蚀试验，系统研究了最佳工艺参数下熔覆层及基体的化学成分、微观组织和性能。结果表明，影响熔覆层宽度和深度的主要因素是激光功率。扫描速度对熔覆层高度也有显著影响。修复结晶器足辊的最佳工艺参数为：激光功率2kW、扫描速度4mm/s、送粉速率15g/min。沿熔覆层深度方向，涂层微观组织由平面晶、胞状晶或树枝晶逐渐转变为等轴晶。基体主要为马氏体并保留奥氏体；共晶相由网状M₂B、颗粒状M(C,B)₆和M₇(C,B)₃相组成。熔覆层硬度显著提高，约为基体硬度的三倍。熔覆层的失重仅为基体失重的一半。其耐磨性能和耐腐蚀性能得到显著提高。激光熔覆修复的足辊工作周期比堆焊修复的足辊长得多。综上所述，激光熔覆技术可以提高结晶器足辊的使用寿命。
