3D激光熔覆铁基合金温度场模拟与试验研究

发布时间：2018-08-30 11:07

【摘要】：3D打印是增材制造的新发展,利用3D打印工艺成形金属构件是机械制造业的重要发展方向。激光熔覆及其成形技术是在激光加工技术的基础上研制成功的一种新的快速成形技术。基于高能激光束的熔覆技术既可以用于基体材料的表面改性,又能对表面磨损零件进行修复和金属构件的成形。激光材料表面改性技术的工艺是一个十分复杂的过程,本文通过对激光熔覆过程温度场的动态模拟来预测最优工艺参数,采取双因素全面试验法对模拟结果进行验证,并对最优工艺参数和搭接率下的熔覆层进行摩擦磨损检测。主要研究内容如下:(1)建立Q235钢表面激光熔覆低碳铁基合金温度场三维模型,考虑了对流、热物性参数、相变潜热和同步送粉特点等因素,分析了熔覆层顶底点温度随时间变化曲线,对熔覆层成形质量进行预测,得出:P=2000 W、v=10 mm/s时,熔覆层顶底点最高温度分别为2300℃和1500℃,有利于得到表面形貌较好、与基体良好冶金结合且稀释率低的熔覆层。对该参数下的不同时刻温度场分布进行分析,看到激光熔覆受热影响的区域小,除熔覆刚开始阶段,熔池周围温度场趋势稳定,熔池最高温度点位于光斑中心和熔池最深处点之间。(2)在3D打印与激光再制造平台成套设备上进行激光熔覆铁基合金的试验研究。确定激光功率和扫描速度作为变量,对不同工艺参数组合下熔覆层几何形状、宏观形貌、微观组织进行检测和分析,结果表明:熔覆层宽度随激光功率的增加而增加,而熔覆层厚度随激光功率的加大呈现双峰状;熔覆层宽度和厚度随着扫描速度的加快而减小。提出了激光线能量密度来说明激光功率和扫描速率的匹配性,对判断熔覆层表面形貌的连续性和过烧有重要意义。结合模拟温度曲线和金相图片,可知熔覆层熔覆区为平面晶和垂直于界面的树枝晶构成,过渡区为富Gr、Ni的板条状马氏体;当P=2000 W、v=10 mm/s时,熔覆区组织均匀致密,过渡区中基体和熔覆材料良好冶金结合且稀释率低,热影响区铁素体与珠光体得到了细化,熔覆层质量优异。(3)采用单道最优工艺参数和合适的搭接率进行多道熔覆,制备出磨削深浅不同的铁基合金小试环,在MVF-1A型立式摩擦磨损试验机上进行等速变载荷、等载荷变速情况下的摩擦磨损试验,结果表明:随着载荷的增加,摩擦系数也增加;随着转速的增大,摩擦系数略微减小。对熔覆层不同深度的显微硬度进行测量,可知随着至表面距离的增加,经历缓慢下降、加速下降、缓慢下降三个阶段,熔覆区外层硬度(350 HV)最高且为基体的2倍。磨痕SEM图片显示,随着载荷加大,黏着磨损加剧;熔覆区磨损机制为磨粒磨损和黏着磨损,过渡区为剥层磨损、黏着磨损和磨粒磨损。
[Abstract]:3D printing is a new development of material increasing manufacturing. It is an important development direction of mechanical manufacturing to use 3D printing technology to form metal components. Laser cladding and its forming technology is a new rapid prototyping technology developed on the basis of laser processing technology. The cladding technology based on high energy laser beam can be used not only to modify the surface of the matrix material, but also to repair the worn surface parts and to form the metal components. The technology of surface modification of laser material is a very complicated process. In this paper, the optimum process parameters are predicted by dynamic simulation of temperature field in laser cladding process, and the simulation results are verified by two-factor comprehensive test method. The friction and wear of the cladding layer under the optimal process parameters and lap ratio were tested. The main research contents are as follows: (1) the temperature field model of laser cladding low carbon Fe-base alloy on Q235 steel surface is established, and the factors such as convection, thermal physical parameters, latent heat of phase transformation and the characteristics of simultaneous powder feeding are taken into account. The temperature variation curve of the top and bottom point of the cladding layer with time is analyzed, and the forming quality of the cladding layer is predicted. It is concluded that the maximum temperature of the top and bottom point of the cladding coating is 2300 鈩，

本文编号：2212880