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Abstract Effect of tempering time on fatigue crack behavior of China Low Activation Martensitic (CLAM) steel was studied at room temperature in air. The fatigue crack growth rates subjected to the tempering time range of 90–9000 min were investigated. The results showed that the fatigue crack growth decelerated in the near-threshold region as the tempering time increased. The fatigue crack growth rate after tempering for 9000 min was approximately one-third of that of the specimen tempered for 90 min with ΔK of 14 MPa m0.5. The improved fatigue crack growth resistance could be explained by the influence of variation in microstructure, i.e., martensitic laths and precipitates. This study suggested that the effective driving force for fatigue crack growth was reduced in the near-threshold region by the activated roughness-induced crack closure mechanism as a result of rougher fracture surface caused by coarsened martensitic laths and precipitates. [ABSTRACT FROM AUTHOR]

Abstract Blanket is the key energy conversion component of a fusion reactor, it is designed with a large number of complex embedded cooling channels to remove the high nuclear heat deposition. Due to the complex inner-channeled structure, the fabrication of the blanket components has been one of the key issues of the blanket technical development. In this study, the selective laser melting (SLM) additive manufacturing (AM) processing was employed to fabricate small scale test blanket module with China low activation martensitic (CLAM) steel, and the hot isostatic pressing (HIP) was applied to improve the microstructure and mechanical properties. The microstructure and mechanical properties of the SLM built CLAM at the as-built, standard heat treatment (SHT) and HIP&SHT status were investigated and evaluated. The results showed that the relative density at the as-built status compared to the hot-rolled CLAM steel reached 99.7%. The tensile strength of the as-built status was 966.2 MPa and 829.1 MPa in the directions vertical and parallel to the building direction, respectively. After the HIP&SHT, the orientation of the microstructure and the difference in strength in different directions decreased. The strength values in the directions vertical and parallel to the building direction were similar, which were equivalent to that of the hot-rolled CLAM steel with SHT. Moreover, the impact absorbed energy in the directions vertical and parallel to the building direction was increased from 21.02 J to 9.18 J at the as-built status to 54.48 J and 18.83 J at the HIP&SHT status, respectively. Meanwhile, micro-defects were drastically decreased with the help of HIP. It could be concluded that the dislocation migration and recrystallization in HIP process is effective to improve the microstructure and mechanical properties of the SLM built CLAM steel. [ABSTRACT FROM AUTHOR]

Exploring tritium permeation barriers with high permeation reduction factor (PRF) by an industrial scale process is crucial for tritium systems in fusion reactors. Herein, we fabricated a dense Fe-Al/Al 2 O 3 coating by a simple hot-dipping aluminizing (HDA) method and optimized oxidation strategy. The microstructure, chemical composition, and crystallographic characteristic of obtained samples were investigated. And the permeation of deuterium through the sample was determined by gas-driven permeation (GDP) experiments. The results show that the obtained oxide coating mainly consisted of γ-Al 2 O 3 layer and Fe Al gradient transition layer. Notably, the Al 2 O 3 layer formed by the oxidation of FeAl alloy coating possessed a high PRF value of 2394 at 550 °C. Compared with the direct oxidation of HDA sample, the oxide coating prepared by the alloy topcoat oxidation strategy was denser and had less defects. Meanwhile, the effect of Al topcoat and different Fe Al alloy topcoats on the microstructure and performance of the oxide coating were investigated, respectively. And the formation mechanisms of oxide coatings prepared by different oxidation strategies were also analyzed. [Display omitted] • A dense Fe-Al/Al 2 O 3 coating was fabricated on CLAM steel. • The Fe Al topcoat was conducive to the growth of the dense coating. • The coating formed on FeAl topcoat possessed the highest PRF value. [ABSTRACT FROM AUTHOR]

Er 2 O 3 coating is one of the candidate tritium permeation barriers (TPB) to reduce tritium permeation and leakage in fusion reactors. A series of Er 2 O 3 coatings were synthesized on China Low Activation Martensitic (CLAM) steel via sol-gel method, and systematic investigate the influence of synthesis parameters for on microstructure and properties of the Er 2 O 3 coatings. The results showed that no cracks were observed in Er 2 O 3 coatings as chosen 11 vol.% diethanolamine. The best heat treatment temperature could be thought 600 °C, in order to obtain a homogeneous and dense Er 2 O 3 coating with high hardness, good crystallization and strong bonding to the substrate. [ABSTRACT FROM AUTHOR]