Additive manufacturing of W/RAFM hypervapotron plasma-facing components and the steady state thermal fatigue behavior

Plasma-facing components (PFCs) have consistently been one of the most crucial elements in modern magnetic confinement nuclear fusion devices. However, conventional metallurgical fabrication methods struggle to achieve the integral shaping of complex structures, and the control of interface strength is another challenging of its own. Additive manufacturing is a highly promising approach capable of achieving one-time forming of various intricate structures. In this study, the structurally optimized tungsten-Reduced Activation Ferritic/Martensitic (RAFM) steel PFCs were prepared using Selective Laser Melting (SLM) technology. Subsequently, the performance of the PFCs was analyzed through thermal fatigue load tests, thermodynamic simulations, and micro-mechanical experiments. The research revealed that the hypervapotron structure can reduce temperatures by >20.6 % compared to circular tubular cooling structures. Simultaneously, direct bonding between tungsten and steel was achieved through additive manufacturing technology. Elements (Fe, W, Cr, C, etc.) could undergo mutual diffusion, gradually reducing the mechanical properties of the interface under thermal loads. Furthermore, stress concentration and thresholds (from 1.18 GPa to 1.59 GPa) were identified on the interface, and cracking occurred when the tensile strength on the interface fell below this value. This indicates that the PFCs module directly connected with W/RAFM by additive manufacturing can withstand a limited cycles of 5 MW/m² fatigue thermal shocks. But if by adding some interlayer elements to prevent the mutual diffusion, mitigate the structural softening effect caused by thermal fatigue, and relieve the interfacial stress, which would mitigate this problem, and should be one of the next development directions for the PFCs fabricated by additive manufacturing. This work provides crucial references for the development of future PFCs.