Duan Xiaoming, Zhuang Jin, Yang Xiaodong
Department of Mechanical Engineering and Automation, Harbin Institute of Technology, Harbin, China.
3D Print Addit Manuf. 2024 Jun 18;11(3):e1141-e1150. doi: 10.1089/3dp.2022.0339. eCollection 2024 Jun.
To overcome the material processing challenges induced by high levels of heat input in wire arc additive manufacturing (WAAM), an innovative WAAM method using pulsed arc plasma (PAP-WAAM), was developed by the authors in the previous study. In this method, the PAP generated by the pulsed voltage was used as the heat source. The pulse interval can be defined as the time interval between adjacent pulse voltages, which determines the ignition time and frequency of the arc plasma, thus influencing the forming process. However, the effect of pulse interval on the forming process has not yet been revealed. Here, the effects of pulse interval on forming process during the PAP-WAAM of Ti6Al4V, including thermal behavior, arc plasma characteristics, and metal transfer process, were investigated by experiments and simulation. The results exhibited that the interpass temperature and maximum peak temperature decrease with increasing pulse interval at the same arc plasma power, indicating an alleviation of heat accumulation along the building direction. As the pulse interval increased, the ignition mode of the arc plasma changed from ignition between the tungsten electrode and the previously deposited layer to ignition between the tungsten electrode and filler wire, which increased the proportion of discharge energy allocated to the filler wire, thus reducing the overall heat input required for material deposition. When the pulse interval was 300 and 400 ms, only the uninterrupted bridging transfer mode was observed during the deposition process. The uninterrupted bridging transfer is considered to contribute to forming a smooth and consistent layer appearance. In addition, longer pulse intervals resulted in less surface oxidation, narrower wall thickness, and better macrostructure, attributed to reduced heat input and improved effective heat dissipation. This research reveals the effect of pulse interval on forming process during PAP-WAAM, which benefits the fabrication of desirable metal parts.
为了克服电弧增材制造（WAAM）中高热输入引起的材料加工挑战，作者在先前的研究中开发了一种使用脉冲电弧等离子体的创新WAAM方法（PAP-WAAM）。在该方法中，由脉冲电压产生的PAP被用作热源。脉冲间隔可定义为相邻脉冲电压之间的时间间隔，它决定了电弧等离子体的点火时间和频率，从而影响成型过程。然而，脉冲间隔对成型过程的影响尚未得到揭示。在此，通过实验和模拟研究了脉冲间隔对Ti6Al4V进行PAP-WAAM过程中成型过程的影响，包括热行为、电弧等离子体特性和金属转移过程。结果表明，在相同电弧等离子体功率下，层间温度和最高峰值温度随脉冲间隔的增加而降低，这表明沿堆积方向的热积累得到缓解。随着脉冲间隔的增加，电弧等离子体的点火模式从钨电极与先前沉积层之间的点火转变为钨电极与填充丝之间的点火，这增加了分配给填充丝的放电能量比例，从而降低了材料沉积所需的总热输入。当脉冲间隔为300和400 ms时，在沉积过程中仅观察到不间断的搭桥转移模式。不间断的搭桥转移被认为有助于形成光滑一致的层外观。此外，较长的脉冲间隔导致表面氧化减少、壁厚变窄和宏观结构更好，这归因于热输入减少和有效散热改善。本研究揭示了脉冲间隔对PAP-WAAM过程中成型过程的影响，这有利于制造理想的金属零件。
