为了满足纯钨块体激光选区熔化致密成型的要求，开展了纯钨基板/粉体单层激光熔化/凝固实验，探索了参数窗口，观察了熔滴球化现象，并运用熔滴铺展/凝固竞争模型解释了球化机制。纯钨熔滴具有较高的粘度和表面张力，铺展过程较慢，且钨的热导率和熔点较高，凝固过程十分迅速，熔滴来不及完成铺展而具有快速凝固球化的倾向。增强基板/粉体对激光的吸收有助于提高熔滴峰值温度并延长凝固时间，从而减弱球化倾向。脉冲激光作用下，相对于扫描速度,调整激光作用时间更加合理。当激光作用时间为300 μs时，由于平衡的熔滴体积和温度梯度，可以形成较为良好的熔化轨迹。

In order to realize the densification behavior of pure tungsten processed by selective laser melting, the single layer laser melting and solidifying of pure tungsten substrate and powder experiments are conducted to find the optimal processing parameters, and the balling phenomenon is observed. The balling process is explained with spreading and solidifying of the molten droplets competition model. The pure tungsten droplets spread at a low speed for their high viscosity and surface tension, but they solidify simultaneously at a high speed driven by the existing steep temperature gradient. Due to their higher thermal conductivity and melting point, the molten droplets solidify entirely before spreading completely and keep their globular geometry instead of creating a flat layer. Increasing the laser absorptivity of powder and substrate helps reduce the balling tendency at the higher peak temperature. Compared with scan speed, adjusting the laser exposure time is more appropriate under pulse laser control. Favorable melt tracks can be fabricated with exposure time of 300 μs, for the balanced melt volume and temperature gradient.