When tungsten is processed by laser powder bed fusion additive manufacturing, the combination of high residual stresses and tungsten’s inherent ductile-to-brittle transition leads to a network of microcracks. While preheating is widely accepted as the most efficient way to reduce residual stresses in additively manufactured parts, thus far it has proven ineffective in completely eliminating microcracking in tungsten. In addition to preheating, changing the alloy composition is an increasingly popular approach to circumvent cracking. This work utilizes in situ high-speed optical imaging combined with thermomechanical modeling to elucidate the effect of preheating and alloying with 2 wt% rare earth oxides on the cracking behavior in powderless single track and hatch strategy laser scans. Optical imaging reveals two distinct cracking mechanisms in the fusion zone and the heat affected zone, both of which are eliminated by substrate preheating temperatures of 773–873 K. Due to the lower melting point of the rare earth oxide inclusions, the melt behavior becomes more turbulent and processing parameters need to be adjusted accordingly, but the cracking characteristics remained the same. The response to preheating was similar for both pure tungsten and the alloys tested in this study; there was no beneficial effect of the alloy additions. This work shows that the fundamental metallurgical cause of microcracking in tungsten can be circumvented, in a step towards structural applications of additively manufactured tungsten.

当通过激光粉末床熔合增材制造加工钨时，高残余应力和钨固有的韧性到脆性转变的结合会导致微裂纹网络。虽然预热被广泛认为是减少增材制造零件残余应力的最有效方法，但迄今为止，它已被证明无法完全消除钨中的微裂纹。除了预热，改变合金成分是一种越来越流行的避免开裂的方法。这项工作利用原位高速光学成像结合热机械建模来阐明预热和合金化与 2 wt% 稀土氧化物对无粉单轨和孵化策略激光扫描中的开裂行为的影响。光学成像揭示了熔合区和热影响区两种不同的开裂机制，两者都被 773-873 K 的基材预热温度所消除。由于稀土氧化物夹杂物的熔点较低，熔体行为变得更多湍流和加工参数需要相应调整，但开裂特性保持不变。纯钨和本研究中测试的合金对预热的响应相似；添加合金没有任何有益效果。这项工作表明，钨微裂纹的根本冶金原因是可以避免的，这是向增材制造钨的结构应用迈出的一步。两者都通过773-873 K的基材预热温度消除。 由于稀土氧化物夹杂物的熔点较低，熔体行为变得更加湍流，需要相应调整工艺参数，但开裂特性保持不变. 纯钨和本研究中测试的合金对预热的响应相似；添加合金没有任何有益效果。这项工作表明，钨微裂纹的根本冶金原因是可以避免的，这是向增材制造钨的结构应用迈出的一步。两者都通过773-873 K的基材预热温度消除。 由于稀土氧化物夹杂物的熔点较低，熔体行为变得更加湍流，需要相应调整工艺参数，但开裂特性保持不变. 纯钨和本研究中测试的合金对预热的响应相似；添加合金没有任何有益效果。这项工作表明，钨微裂纹的根本冶金原因是可以避免的，这是向增材制造钨的结构应用迈出的一步。但开裂特性保持不变。纯钨和本研究中测试的合金对预热的响应相似；添加合金没有任何有益效果。这项工作表明，钨微裂纹的根本冶金原因是可以避免的，这是向增材制造钨的结构应用迈出的一步。但开裂特性保持不变。纯钨和本研究中测试的合金对预热的响应相似；添加合金没有任何有益效果。这项工作表明，钨微裂纹的根本冶金原因是可以避免的，这是向增材制造钨的结构应用迈出的一步。