Abstract
Plate-type heat exchangers are anticipated to be used in the next-generation nuclear industry, and solid-state diffusion welding is a critical technology for building plate-type heat exchangers with high integrity. In this study, we manufactured a diffusion weldment and evaluated its creep behavior. Microscopic analysis revealed that Al-rich oxides were developed along the interface, significantly impeding grain-boundary movement across the interface. Oxide-containing planar grain boundaries resulted in premature brittle fracture at the interface with less than 9% creep strain under all test conditions. The time to rupture and time to 1% creep strain of the diffusion weldment were less than those of the as-received alloy, while the slopes in double-logarithmic plots were almost identical for both alloys. In a Larson–Miller parameter study, the stress to rupture of the diffusion weldment reached 95.59% of that of the as-received alloy, whereas the stress to 1% creep strain steeply decreased in the low-stress range.
Highlights
Plate-type heat exchangers have attracted much attention for application in the nextgeneration nuclear industry because they can realize high heat-transfer efficiency between primary and secondary systems [1,2,3]
Diffusion welding with Alloy 617 was investigated for application to compact heat exchangers in the next-generation nuclear industry
The following conclusions can be drawn from the microscopic analysis and experimental stress-rupture tests
Summary
Plate-type heat exchangers have attracted much attention for application in the nextgeneration nuclear industry because they can realize high heat-transfer efficiency between primary and secondary systems [1,2,3]. Solid-state joining methods, such as brazing, transient liquid phase bonding, and diffusion welding, are essential processes for manufacturing such plate-type heat exchangers. Brazing [4,5,6,7,8,9,10] and transient liquid phase bonding [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] are attractive for joining. Luo et al used a BNi-2 filler metal to join Hastelloy. Jalilian et al studied the influence of the process parameters (filler metal thickness and holding time for isothermal solidification) of transient liquid phase bonded Inconel 617 (UNS N06617) using BNi-3 (Ni-4.5Si-3B) [12] and BNi-6 (Ni10P) [19].
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