增材方向对激光粉末床熔融钨材料高热负荷性能的影响

Effect of building direction on the behavior of laser powder bed fused tungsten under high heat load

摘要:

激光粉末床熔融（LPBF）作为一种新兴的增材制造技术，为未来聚变堆偏滤器mono-block的制备提供了新的成形方法。本研究利用LPBF，采用水平增材和竖直增材两种方式对纯钨样品进行了制备。研究发现，在15 MW/m2的热负荷下，竖直增材样品发生了明显的熔化和飞溅现象，水平增材样品只发生少许开裂和轻微溅射。通过微观组织表征发现，LPBF过程中不同方向组织的差异导致了钨热导率的各向异性。对于水平增材样品，热流方向平行于增材方向，沿该方向生长的柱状晶有利于热量传导；对于竖直增材样品，热流方向垂直于增材方向，晶界及以网格状分布的裂纹阻碍热量传导，热量在表面积累并导致熔化。因此，本研究表明，增材方向对利用LPBF制备偏滤器mono-block部件有着重要的影响。

Abstract:

As a novel additive manufacturing technique, laser powder bed fusion (LPBF) provides a new forming method for the fabrication of divertor mono-block for the future nuclear fusion reactor. In this study, pure tungsten samples were built by the LPBF technique horizontally and vertically. It is found that under the heat load of 15 MW/m2, there were severe melting and sputtering in the vertically built samples, while only a little cracking and sputtering occured in the horizontally built samples. It is believed that the anisotropy of the thermal conductivity in LPBFed tungsten samples is caused by the microstructure difference in different directions. For the horizontally built sample, the direction of the heat flow is parallel to the building direction, and the coarse columnar grains grown along this direction is favorable for heat conduction. For the vertically built sample, the heat flow direction is perpendicular to the building direction, grain boundariesand the crack network would hinder the heat conduction. Therefore, the heat accumulated on the surface of vertically built sample could cause melting. This study shows that the building direction has an unavoidable impact on the fabrication of divertor mono-block using the LPBF technique.