| 引用本文: | 王海楠,程延海,马昆,杨金勇,于海航.后处理对高速激光熔覆表面性能的影响∗[J].中国表面工程,2023,36(5):88~99 |
| WANG Hainan,CHENG Yanhai,MA Kun,YANG Jinyong,YU Haihang.Effect of Post-treatment on Coating Surface Properties of High-speed Laser Cladding[J].China Surface Engineering,2023,36(5):88~99 |
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| 后处理对高速激光熔覆表面性能的影响∗ |
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王海楠1, 程延海1, 马昆1,2, 杨金勇1, 于海航1
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1.中国矿业大学机电工程学院 徐州 221116;2.国家能源集团宁夏煤业有限责任公司 银川 751410
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| 摘要: |
| 液压立柱表面镀铬涂层易出现微小裂纹并导致涂层剥落，对煤矿生产造成安全隐患。为强化液压立柱表面性能、提高液压立柱使用寿命，利用高速激光熔覆技术在 27SiMn 钢表面制备铁基耐腐蚀熔覆层，并对熔覆层进行车-滚后处理提升强化熔覆层表面性能。使用扫描电子显微镜、形状测量激光显微镜、显微硬度计、电化学工作站等对高速激光熔覆层、车削及不同滚压力作用后的熔覆层微观组织、表面粗糙度、残余应力、显微硬度、耐腐蚀性能进行研究分析。结果表明：初始熔覆层显微组织致密，无明显孔隙、裂纹等缺陷，从结合处到表面依次为平面晶、树枝晶、等轴晶；滚压加工的“削峰填谷”效应使熔覆层表面发生塑性变形，滚压力为 2.8 MPa 时，表面轮廓平整，表面粗糙度降低至 0.768 μm；熔覆层硬度随滚压力的增大而增加，熔覆层顶部出现明显的塑性变形区和硬化层；车-滚复合加工使熔覆层表面残余应力由拉应力状态转变为压应力， 滚压力增大，残余压应力先增大后减小；车-滚复合加工使熔覆层表层晶粒细化，增强 Cr 元素扩散，提高耐蚀能力，但过大的滚压力使熔覆层表面损伤，耐蚀能力下降。车-滚后处理工艺有效提升了熔覆层表面性能，可为高速激光熔覆高效低成本的后处理工艺研发提供参考。 |
| 关键词: 高速激光熔覆 后处理 表面粗糙度 滚压 显微硬度 |
| DOI：10.11933/j.issn.1007?9289.20221203003 |
| 分类号:TG156 |
| 基金项目:国家重点研发计划（2023YFE0201600）；中央高校基本科研业务费专项（2021ZDPY0223）；江苏高校优势学科建设工程资助项目 |
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| Effect of Post-treatment on Coating Surface Properties of High-speed Laser Cladding |
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WANG Hainan1, CHENG Yanhai1, MA Kun1,2, YANG Jinyong1, YU Haihang1
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1.School of Mechanical and Electrical Engineering, China University of Mining and Technology,Xuzhou 221116 , China;2.China National Energy Group Ningxia Coal Industry Co., Ltd., Yinchuan 751410 , China
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| Abstract: |
| Electroplating is widely used to strengthen the surfaces of hydraulic columns. However, chromium plating is sensitive to minor cracks, causing the coating to peel or even flake off in the harsh and humid underground working environment of coal mines. As a result, the hydraulic column easily corrodes and seriously threatens the safety of coal mine production. High-speed laser cladding, an emerging environmentally friendly surface technology, is one of the most promising surface coating technologies as an alternative to hard chrome plating. To strengthen the surface properties and increase the service life of the hydraulic column, high-speed laser cladding technology was employed to prepare Fe-based corrosion-resistant coatings on the surface of 27SiMn steel in this study. This was followed by post-treatment involving turning and rolling the cladding layer to enhance and improve the surface properties of the coating. The microstructure, surface roughness, residual stresses, microhardness, and corrosion resistance of the coatings were analyzed using scanning electron microscopy(SEM), profiling laser microscopy, microhardness testing, and an electrochemical workstation for high-speed laser cladding, turning, and rolling. The results show that the initial coating has a dense microstructure with no obvious defects such as pores and cracks, and that planar crystals, dendrites, and equiaxed crystals exist sequentially from the bond to the surface. The high overlap rate of the high-speed laser cladding causes the coating surface to form a multilayer cladding and promotes the formation of small, reticular, equiaxed crystals at the overlap. After turning, the surface profile of the coating was wavy, the wave crests were sharp, and sharp depressions appeared at the troughs that were centrally symmetrical to the wave crests. The surface grains of the coating exhibited obvious plastic deformation, but the degree of deformation of the grains in the respective area was nonuniform. The surface of the coating was plastically deformed by the peak-averting and valley-filling effect of the rolling process. When the rolling pressure is 2.8 MPa, the surface profile is flat with the surface roughness reduced to 0.768 μm. However, as the rolling pressure is increased to 3.8 MPa, scratches appear in some areas of the coating surface with the surface roughness increasing to 0.988 μm. The coating hardness increased with the rolling pressure, with a significant plastic deformation zone and a hardened layer appearing at the top of the coating, increasing to 525.1 HV at 3.8 MPa. However, rolling strengthening has almost no effect on the bonding area between the coating and substrate, and the hardness value of the coating is close to the change in the rolling pressure. The residual stress on the coating surface was transformed from tensile to compressive by a combination of turning and rolling processes. As the rolling pressure increased, the residual compressive stress on the coating surface initially increased and then decreased. The maximum surface residual compressive stress was 846.3 MPa at the rolling pressure of 2.8 MPa. The combination of the turning and rolling processes causes plastic deformation of the coating surface, resulting in grain refinement and work hardening. Grain refinement improves the diffusion of Cr and forms a dense passivation film on the coating surface, preventing an increase in corrosion and improving the corrosion resistance. At rolling pressures up to 3.8 MPa, the work-hardening effect is significant. However, the surface of the coating deformed because of the large bending and deflection of the crystal structure, causing surface damage and increasing the surface roughness, which ultimately reduces the corrosion resistance of the coating. The post-treatment processes of turning and rolling effectively enhanced the surface properties of the coating, and provides a reference for the research and development of high-efficiency and low-cost post-treatment processes for high-speed laser claddings. |
| Key words: high-speed laser cladding post-treatment surface roughness rolling microhardness |
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