Microstructure and property of 1.6%C ultrahigh carbon steel after laser surface treating
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摘要: 为了研究激光处理后超高碳钢表面组织及性能的变化,采用2kW连续横流CO2激光器对超高碳钢(C的质量分数为0.016)进行了激光处理,采用扫描电镜观察组织和显微硬度计测量深度方向显微硬度值的方法,进行了理论分析和实验验证,取得了沿深度方向的组织照片和硬度分布曲线。结果表明,激光处理层分为熔凝层、过热层和相变硬化层。熔凝层可观察到胞状树枝晶和离异共晶;相变硬化层组织细小,显微硬度(高达750HV～905HV)高于其它层,是典型的激光淬火组织。随激光功率增大(1000W～1200W),熔凝层中胞状树枝晶和离异共晶增多并细化,马氏体数量减少,各层的宽度、深度均增大,显微硬度降低。这一结果对细化超高碳钢组织和改善其性能是有帮助的。Abstract: In order to study the surface microstructure and property variation of ultrahigh carbon steel after laser treating,ultrahigh carbon steel(mass fraction of C is 0.016) was treated with 2kW continuous wave CO2 laser.Then its microstructure was observed with a scanning electron microscope and its hardness was measured with a microhardness tester.Through theoretical analysis and experiments verification,the microstructure and microhardness curve along the depth direction were obtained.The results show that the laser treated layer includes surface melted layer,overheating layer and transformation hardening layer.The melted layer is composed of cystiform-dendritic and divorced eutectic.The grain size in transformation hardening layer is finer than that in other layers,its microhardness is higher and its hardness can reach 750HV～905HV,which indicates a typical laser quenching microstructure.With the increase of laser power (1000W～1200W),the volume fraction of cystiform-dendritic and divorced eutectic in melted layer increased,however the quantities of martensite decreased,each layer's width and depth were reduced,and microhardness decreased.It is helpful to refine microstructure of ultrahigh carbon steel and improve its property.
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Keywords:
- laser technique /
- surface hardening /
- laser treating /
- ultrahigh carbon steel /
- microstructure
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