超高速激光熔覆成形M2涂层*

为修复受损轧辊、提高轧辊使用寿命，利用超高速激光熔覆技术，在 9Cr2Mo 钢表面熔覆成形 M2 高速钢制备的涂层。 为提高熔覆层质量，设计正交试验与对比试验，并借助光学显微镜、扫描电子显微镜、显微硬度计，对不同扫描速度、激光功率、道次间距条件下熔覆层的宏观形貌、微观组织、显微硬度进行研究分析。结果表明，扫描速度对宏观平整度影响最大， 提高扫描速度、降低激光功率、增大道次间距可提高涂层平整度；确定最优工艺参数为：激光功率 1.5 kW，扫描速度 35 m / min， 道次间距 0.30 mm 的组合和激光功率 1.7 kW，扫描速度 35 m / min，道次间距 0.35 mm 的组合；熔覆层组织细小、成分均匀， 主要为等轴晶，晶粒边界出现网状碳化物；熔合线处晶粒尺寸较为细小，熔覆道中部组织相对较大，道次间熔合线下方组织粗化明显；制备的 M2 涂层显微硬度整体高于基体，且具有较好的耐磨性。

M2 Coatings Formed by Extreme High Speed Laser Cladding

In order to repair damaged rolls and increase the service life of the roll, extreme high speed laser cladding technology is used to form coatings prepared by M2 HSS steel on the surface of 9Cr2Mo steel. In order to improve the quality of cladding layer, orthogonal experiment and contrast experiment are designed. With the help of optical microscope, scanning electron microscope and microhardness tester, the macro morphology, microstructure and microhardness of cladding layer under different scanning speed, laser power and pass spacing are studied and analyzed. The results show that the scanning speed has the greatest impact on the macroscopic flatness. Increasing the scanning speed, reducing the laser power, and increasing the pass spacing can improve the coating flatness. The optimal process parameters are determined as follows: laser power 1.5 kW, scanning speed 35 m / min, pass spacing of 0.30 mm and 1.7 kW laser power, scanning speed 35 m / min, pass spacing 0.35 mm. The cladding layer has a fine structure and uniform composition, mainly equiaxed crystals, and network carbides appear on the grain boundaries. The grain size of fusion lines is relatively small, the structure in the middle of the cladding pass is relatively large, and the structure under the fusion line between passes is coarsened obviously; the microhardness of the prepared M2 coating is higher than that of the substrate, and it has better wear resistance.