Abstract
In this paper, diffusion bonding was adopted to join 9Cr martensitic/ferritic heat-resistant steels using an electrodeposited Ni interlayer with a thickness of 40 μm. In addition, the effect of tempering treatment after diffusion bonding on the microstructure evolution and mechanical properties of the bonding joints was investigated. It was found that a transition region with face-centered cubic (FCC) structure was formed between the steel and Ni interlayer. The transition region was the solid solution of (γFe,Ni) rich in Ni component, being related to martensite in the base metal by the Kurdjumov–Sachs (K-S) orientation relationship. No intermetallic compounds were detected at the bonding joints before and after tempering treatment. After tempering treatment, the transition region had higher dislocation density than other regions, due to the higher pinning effect of solute atoms acting on the dislocation than that of the matrix. Tensile tests indicated that tempering treatment improved the mechanical properties of the joint, since the samples after tempering treatment fractured in the base metal, whereas the specimens without tempering treatment fractured at the joint interface.
Highlights
Nuclear energy has been considered preferentially to meet energy shortages and environmental stewardship challenges in the future owing to its abundance, environmental compatibility, cost-effective operation, and zero carbon emissions [1,2]
In order to join this steel to the same steel or other materials, a variety of fusion welding technologies have been employed, including electron beam (EB) welding [7,8], laser welding [8], hybrid welding [8,9], and tungsten inert gas (TIG) welding [10,11]
Part is the interlayer of nickel and the joints contrast was and opposite tempering treatment
Summary
Nuclear energy has been considered preferentially to meet energy shortages and environmental stewardship challenges in the future owing to its abundance, environmental compatibility, cost-effective operation, and zero carbon emissions [1,2]. The 9Cr martensitic/ferritic heat-resistant steel has been selected as the primary candidate structural material for blanket components in nuclear reactors due to its outstanding comprehensive performance, such as low thermal expansion coefficient, high thermal conductivity, and favorable radiation swelling resistance in a high-radiation-flux environment [3,4,5,6]. The welding techniques are critical to the practical application of 9Cr martensitic/ferritic heat-resistant steel in nuclear reactors. Fusion welding will change the microstructure of the matrix adjacent to the weld bead. Traditional fusion welding usually involves the microstructure gradients in the heat-affected zones of welds, which include overtempered regions, intercritical regions, fine-grain regions, and coarse-grain regions [12]
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