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激光立体成形技术是一项基于同步送粉激光熔覆的先进制造技术。激光立体成形和修复过程中沉积层、热影响区以及基体材料组织、性能的差异将对最终零件的性能,尤其是疲劳性能产生重要影响。为改善基体、热影响区(HAZ)的组织、性能差异,针对TC4合金,提出在激光沉积前对基材表面进行多次激光重熔扫描预处理,从而优化基材热影响区组织性能。基于此,通过研究不同工艺条件下,多次激光重熔处理对热影响区组织性能的影响。结果表明:首先,多次激光重熔将引起的基材热影响区总体冷却速率下降,从而有效的消除热影响区的急冷组织;其次,重熔处理产生的多次热循环对基材热影响区的时效处理对于热影响区的组织、性能(硬度)也有一定的影响。通过在多层沉积前对基材进行适当的激光多次重熔扫描处理有效改善了沉积区、热影响区以及基材性能的大幅波动,实现了均匀渐变。
Laser stereolithography is an advanced manufacturing technology based on simultaneous powder feeding laser cladding. Differences in the properties of the deposited layer, the heat-affected zone, and the matrix material during laser three-dimensional forming and repairing will have a significant impact on the final part properties, especially fatigue properties. In order to improve the microstructure and heat-affected zone (HAZ) microstructure and properties of TC4 alloy, several laser remelting scanning pretreatments of substrate surface before laser deposition were proposed to optimize the microstructure and properties of HAZ. Based on this, the effects of multiple laser remelting treatments on the microstructure and properties of the HAZ under different process conditions were studied. The results show that: firstly, the total cooling rate of the HAZ of the substrate decreases due to the multiple laser remelting, so that the quenching structure in the HAZ can be effectively eliminated. Secondly, the thermal effects of multiple thermal cycles caused by the remelting treatment on the substrate Zone aging treatment for the heat affected zone of the organization, performance (hardness) also have a certain impact. By performing appropriate laser multiple remelting scanning of the substrate prior to multilayer deposition, the dramatic fluctuations in deposition, heat affected zone, and substrate performance are effectively achieved, achieving a uniform gradual change.