Li Yang, Long Hongyu, Wei Bo, Zhou Jun, Lin Feng
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
Institute of Laser Intelligent Manufacturing and Precision Processing, School of Mechanical Engineering, Guangxi University, Nanning 530004, China.
Materials (Basel). 2024 Nov 20;17(22):5667. doi: 10.3390/ma17225667.
In additive manufacturing, controlling hot cracking in non-weldable nickel-based superalloys poses a significant challenge for forming complex components. This study introduces a multiple preheating process for the forming surface in electron beam powder bed fusion (EB-PBF), employing a dual-band infrared surface temperature measurement technique instead of the conventional base plate thermocouple method. This new approach reduces the temperature drop during forming, decreasing surface cooling by 28.6% compared to traditional methods. Additionally, the precipitation of carbides and borides is reduced by 38.5% and 80.1%, respectively, lowering the sensitivity to liquefaction cracking. This technique enables crack-free forming at a lower powder bed preheating temperature (1000 °C), thereby improving the powder recycling rate by minimizing powder sintering. Microstructural analysis confirms that this method reduces low-melting eutectic formation and alleviates liquefaction cracking at high-angle grain boundaries caused by thermal cycling. Consequently, crack-free IN738 specimens with high-temperature durability were successfully achieved, providing a promising approach for the EB-PBF fabrication of crack-resistant IN738 components.
在增材制造中，控制不可焊接镍基高温合金中的热裂纹对复杂部件的成型构成了重大挑战。本研究介绍了一种用于电子束粉末床熔融（EB-PBF）成型表面的多重预热工艺，采用双波段红外表面温度测量技术取代传统的基板热电偶方法。这种新方法减少了成型过程中的温度下降，与传统方法相比，表面冷却降低了28.6%。此外，碳化物和硼化物的析出分别减少了38.5%和80.1%，降低了对液化裂纹的敏感性。该技术能够在较低的粉末床预热温度（1000°C）下实现无裂纹成型，从而通过最小化粉末烧结提高粉末回收率。微观结构分析证实，该方法减少了低熔点共晶的形成，并减轻了热循环导致的高角度晶界处的液化裂纹。因此，成功制备出具有高温耐久性的无裂纹IN738试样，为抗裂纹IN738部件的EB-PBF制造提供了一种有前景的方法。
