Microstructure, mechanical properties and oxidation resistance of bulk W-B-Fe-Cr for fusion shielding

In this work, the bulk W-B-Fe-Cr shielding material with lower boron content (9.6 at.%) has been fabricated by hot isostatic pressing (HIP) for potential engineering application in compact fusion reactor. Microstructure, mechanical properties and oxidation resistance of W-B-Fe-Cr were systematically investigated. By HIP sintering at 1250 ℃, the uniform, dense and crack-free microstructure of W-B-Fe-Cr was obtained. The results of phase analysis show that W-B-Fe-Cr is mainly composed of W, (Fe,Cr)WB and (Fe,Cr)7W6. In range of 500 °C to 1000 °C, the low-boron W-B-Fe-Cr possesses higher flexural strength than reported high-boron (16~30 at.%) W2B-W owing to its W-rich composition, which can more effectively exploit both the toughness of the W phase and the hardening effect of the boride phase. The results show that although the neutron shielding property is degraded by the reduction of boron content, the strength is enhanced conversely. Therefore, for W-B based shielding RSBs, the prudent balancing between shielding capability and mechanical performance is essential for the design of boron content. For evaluation of oxidation resistance of W-B-Fe-Cr, the bare one and Si-coated counterpart were subjected to oxidation tests in air at 1000 ℃. Owing to the fact that underlying WSi2-(FeWCr)Six dual-phase reaction layer was formed by coating Si, which was transformed into the dense SiO2 protective film at high temperature to effectively prevent exposure of the substrate. In the conclusion, the scientific discoveries and constraints of the low-boron W-B-Fe-Cr research was systematically summarized, and the prospective strategies for mechanical performance optimization in high-boron derivatives was overviewed.