The preliminary conceptual design of both the blanket and the divertor of the future DEMO reactor envisages tungsten as plasma-facing material joined to Eurofer 97 steel as the structural element. Therefore, the development of new joining technologies to constitute these first wall components has become an essential task in the fusion community. In this regard, there is a lack of knowledge on the thermal stability and mechanical behaviour of these W-Eurofer 97 joints under the expected service temperatures, which will be situated around 400-600°C. In this paper, successful diffusion brazing of Eurofer 97 steel with tungsten was achieved by using a copper interlayer. Its microstructure, hardness and flexural strength were investigated for different configurations and thermal histories in its predicted operating temperature range.

Investigations on as-brazed specimens showed defect-free interfaces and a continuous metallic bond between W and Eurofer 97 was successfully accomplished; although the hardening of steel base material was detected after joining. Microstructure alterations were observed just at the W-Eurofer 97 interface, with the diffusion of Cu braze into the iron grain boundaries and the formation of a Fe-rich hard intermetallic layer, which was, in fact, the weakest part of the joint during thermo-mechanical testing.

The flexural strength of the brazed specimens at room temperature was relatively low, with a strong dependence on the anisotropy of the W base material and little influence of the stress-relieving thermal treatment. However, testing at temperatures up to 600°C showed high strength of the bonded specimens, with values as high as 470 MPa, comparable to those of the Eurofer 97 steel.

橡皮布和未来的DEMO反应堆的分流器的初步概念设计都将钨作为等离子材料与Eurofer 97钢结合在一起作为结构元素。因此，开发新的连接技术以构成这些第一壁组件已成为融合社区的一项重要任务。在这方面，对于这些W-Eurofer 97接头在预期的使用温度（约400-600°C）下的热稳定性和机械性能缺乏了解。在本文中，通过使用铜中间层，成功实现了Eurofer 97钢与钨的扩散钎焊。在预测的工作温度范围内，针对不同的构造和热历史研究了其微观结构，硬度和抗弯强度。

对钎焊试样的研究表明无缺陷的界面，并且成功地完成了W和Eurofer 97之间的连续金属结合。接合后检测出钢基材的硬化。仅在W-Eurofer 97界面处观察到微观结构变化，Cu钎焊扩散到铁晶粒边界中，并形成了富铁的硬金属间化合物层，实际上，这是热过程中接头的最薄弱部分。机械测试。

室温下钎焊试样的抗弯强度相对较低，与W基体材料的各向异性密切相关，而消除应力热处理的影响很小。但是，在高达600°C的温度下进行的测试表明，粘结试样的强度很高，其值高达470 MPa，与Eurofer 97钢相当。