利用有限元软件ANSYS对激光束扫描试样的温度场进行数值模拟,研究其温度分布规律.研究激光束扫描对试样显微组织和性能的影响,探讨激光功率和扫描速度等工艺参数对相变硬化层组织性能的影响.采用光学显微镜分析45钢激光相变硬化区的显微组织,用显微硬度计进行硬度测量.结果表明:45钢经激光束扫描后,硬化层的显微组织为针状或板条状的马氏体,组织更加均匀、细小,试样表面硬度最高可达57.5 HRC,相比调质处理提高约l倍,激光扫描区域组织沿深度方向上成梯度分布规律,从表层往深度方向依次为相变硬化区、过渡区和基体.激光工艺参数对硬化层显微组织和性能有较大的影响,相变硬化层的深度和宽度随着激光功率的增加而增加,随着扫描速度的增加而减小;硬化层的截面硬度随着激光功率和扫描速度的增加呈现先增加后减小的变化规律.
Temperature field of the specimen was calculated by finite element software-ANSYS.The influence of laser beam scanning on microstructure and properties of the specimen was studied.The effect of laser beam processing parameters,such as laser power,scanning velocity,on microstructure and mechanical properties of transformation hardening layer was discussed.The microstructure of transformation hardening layer of 45 steel was analyzed by metallographic microscope,and the hardness was measured by microhardness test.The results show that microstructure of the hardened layer is composed of needle or lathe martensite by laser beam scanning and the microstructure becomes more uniform and fine.The maximum value of specimen's surface hardness is 57.5 HRC which is approximately 2 times than that of treated with quenching and tempering.Microstructure in the laser scanning area presents gradient distribution in the deep direction and there exists transformation hardened area,transition region and matrix.Laser processing parameters have great influence on microstructure and properties of the hardened layer.The deep and width of the hardened layer increase with laser power increasing,decrease with scanning velocity increasing.The hardness of the hardened layer increases first and then decreases with laser power and scanning velocity increasing.
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