摘要
目的 解决送粉式增材制造TC4波纹度大、粗糙度大的问题。方法 根据皮秒激光、飞秒激光的去除效率差异,以及振镜、物镜瑞利长度的变化对材料峰谷距离去除效果的不同,提出一种多激光异步抛光工艺。首先将皮秒激光与振镜组合进行激光去除,降低材料表面明显的峰谷距离,然后借助飞秒激光与物镜组合进行激光二次去除,进一步降低材料表面残存的峰谷距离,得到较为平整的表面,最后通过连续激光重熔降低材料表面粗糙度。为了直观体现加工过程中材料峰谷距离的变化,首先在TC4表面铣削,形成深度250μm的凹槽,以此模拟波峰、波谷,并进行参数化实验,得到多激光异步抛光的最优工艺参数,最后使用相同加工参数对送粉式增材制造的TC4进行多激光异步抛光研究,并分析抛光前后材料粗糙度、残余应力的变化。结果 采用多激光异步抛光工艺可以使送粉式增材制造TC4表面粗糙度由7.637μm降至0.744μm,同时在多激光异步抛光过程中材料表面残余拉应力呈现先增大后减小的趋势。结论 这种多激光异步抛光工艺解决了送粉式增材制造TC4的表面质量问题,使材料表面可以达到较小的粗糙度。
Additive manufacturing technology is developing rapidly because it can process a variety of complex feature parts that are difficult to manufacture by traditional processes.However,components produced by laser metal deposition,particularly TC4 titanium alloy,often exhibit poor surface quality characterized by significant waviness with high peak-valley distances.Conventional laser remelting polishing methods show limited effectiveness in improving these surface irregularities.To address these issues,the work aims to propose a multi-laser asynchronous polishing method,leveraging the distinct material removal efficiencies of picosecond and femtosecond lasers,as well as the varied peak-valley removal effects induced by differences in Rayleigh lengths between galvanometer scanners and objective lenses.First of all,the laser removal was carried out by the combination of picosecond laser and galvanometer.With the high efficiency of the picosecond laser and the high speed of the galvanometer,the obvious peak-valley distance on the surface of the material was quickly removed.Then,the secondary laser removal was carried out with the combination of femtosecond laser and objective lens.Due to the higher removal accuracy of the femtosecond laser and the smaller Rayleigh length of the objective lens,the precise removal of peak and valley materials was achieved when materials containing peaks and valleys were processed.Therefore,the residual peak-valley distance of the material surface was further reduced with the femtosecond laser and objective lens,resulting in a relatively flat surface.Finally,the surface roughness of the material was reduced by continuous laser remelting.In order to intuitively reflect the changes in the peak-valley distance of the material during the multi-laser asynchronous polishing,the surface of TC4 was first milled to form a 250μm deep groove.In order to simulate the peak and valley,the parametric experiments were carried out to obtain the optimum parameters of the multi-laser asynchronous polishing.Ultimately,the same processing parameters were used to manufacture TC4 by laser metal deposition.The changes in material roughness and residual stress before and after multi-laser asynchronous polishing were analyzed.This multi-laser asynchronous polishing technology reduced the surface roughness of TC4 manufactured by laser metal deposition from 7.637μm to 0.744μm.Meanwhile,it was found that the residual tensile stress on the surface of the material increased first and then decreased in multi-laser asynchronous polishing stages.After picosecond laser removal,the surface residual tensile stress of the material increased to 1000 MPa.Subsequent femtosecond laser treatment further elevated the residual stress to 1146 MPa.However,following the continuous laser remelting,the residual tensile stress was reduced to 934 MPa.This was mainly caused by the different temperature gradients formed in multi-laser asynchronous polishing,in which the picosecond laser and femtosecond laser had shorter action times and larger surface temperature gradients,while the continuous laser had a relatively uniform temperature gradient due to the continuous heating of the material surface.The multi-laser asynchronous polishing method can effectively solve the surface large waviness and high roughness problem of TC4 manufactured by laser metal deposition,so that the surface of the material can reach a small roughness,providing a new idea for the post-treatment of TC4 parts manufactured by laser metal deposition.
作者
宋宇阳
周静
SONG Yuyang;ZHOU Jing(School of Mechanical Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China)
出处
《表面技术》
北大核心
2025年第17期174-182,共9页
Surface Technology
