激光金属直接成形中形貌自稳定效应的研究

Self-Regulation-Effect in Laser Direct Metal Manufacturing

为了在开环控制条件下直接制备出表面平整的薄壁零件,针对同轴送粉条件下粉末离焦对单道熔覆层厚度的影响,建立了理论模型,分析了成形表面出现的凹凸不平现象,对激光离焦和粉末离焦对单道熔覆层形貌的影响进行了实验研究.研究表明,激光离焦主要影响单道熔覆层的宽度,而粉末离焦主要影响单道熔覆层的厚度.在粉末负离焦条件下,激光金属直接成形过程具有形貌自稳定效应,能消除成形层的凹凸现象,从而制造出成形表面平整的薄壁零件样件.由于计算结果与实验结果的趋势能保持一致,形貌自稳定效应能够提高开环系统下薄壁零件的制造精度,因此具有实际的应用价值.

To fabricate fine thin-wall parts with smooth surface by open-loop laser direct metal manufacturing （LDMM） system, the uneven formed surface in forming process is analyzed and the effect of off-focused laser and off-focused powder on the shape of singletrace cladding layer, is investigated by single-trace cladding experiments. The results show that off-focused laser exerts a significant effect the thickness of single-trace cladding layer, and off-focused powder affects mainly the height of single-trace cladding layer. It is suggested that self-regulation-effect in the process of LDMM in the condition of negative off-focused powder enables to perfect the un- even shaped surface caused by instability of process parameters. The theoretical model of the influence of off-focused powder on deposition thickness in the condition of coaxial powder feeding is constructed, and regular pattern obtained from the model matches well with experimental re- sults. Several thin-wall parts with smooth formed surface are fabricated in terms of the self- regulation-effect.