Experimental Investigation of EU-DEMO Breeding Blanket First Wall Mock-Ups in Support of the Manufacturing and Material Development Programmes

This paper presents the testing campaign of the two First Wall mock-ups in the HELOKA facility, one mock-up having a 3 mm thick Oxide Dispersion Strengthened (ODS) steel layer on its surface and the other featuring a tungsten functionally graded cover. Special consideration is given to the diagnostics used for these tests, in particular, the measurement of the surface temperature of the tungsten functionally graded layer with an infrared camera. Additionally, the paper looks into the uncertainty associated with the calorimetric evaluation of the applied heating power for these experiments.

Fatigue Strength Improvement Due to Alloying Steel Weld Toes With WC-Tool Constituent Elements Through Friction Stir Processing

Friction stir processing (FSP) enables surface modifications using a rotational tool and can likely be applied as a new post-weld treatment for improving fatigue strength. When applying FSP to high strength materials, tool wear occurring at the interface between the tool tip and the topmost steel layer has been regarded as an unavoidable issue and is related to the tool rotational speed. The present study investigated the relationship between the tool rotational speed and fatigue strength of arc-welded high-strength low-alloy (HSLA) steel joints with weld toes subjected to FSP using a spherical-tip WC tool. FSP was conducted on the weld toe of HSLA steel joints with various tool rotational speeds. Tool wear increased with increase in tool rotational speed, and consequently contents of constituent elements of the WC tool increased in the topmost steel layer of weld toes, leading to large increase of fatigue strength. One reason for the increase with tool rotational speed is significant increase of solid solution hardening due to supersaturated W and C in the topmost steel layer consisting of martensite laths. The hardened topmost steel layer prevented fatigue crack initiation, and the increased fatigue strength depended on the contents of supersaturated W and C.

Fine structure of low-carbon steel after electrolytic plasma treatment

This work shows the results of research of the fine and dislocation structure of the transition layer of 18CrNi3Mo low-carbon steel after the influence of electrolytic plasma. Conducted research has shown that the modified steel layer, as a result of carbonitriding, was multiphase. Quantitative estimates were made for carbonitride М23(С,N)6 in various morphological components of α-martensite and on average by material in the transition layer of nitro-cemented steel. It was established that α-phase is tempered martensite after nitrocementation. Released martensite is represented by batch, or lath and lamellar low-temperature and high-temperature martensite. Inside the tempered martensitic crystals, lamellar cementite precipitates are simultaneously present, and residual austenite is found along the boundaries of the martensitic rails and plates of low-temperature martensite. It was determined that inside the crystals of all morphological components of α-martensite there are particles of carbonitride М23(С,N)6.

Strain Hardening Behavior of Laminate Structure With Stable bcc/fcc Bimetal Interfaces

This work developed a well-bonded bcc/fcc bimetal interphase, which was produced by a two-step process involving diffusion bonding and conventional rolling. The high-quality interface maintained its integrity even at fracture. The earlier tensile instability in the core steel layer was constrained by the neighboring stable Cu layers on both sides, leading to extra strain hardening and consequently higher ductility. An increase in twin density or slip bands and shear deformation between the layers might be the primary causes for the observed hardening behaviors in the near-interface regions.

Minimizing the Micro-Edge Damage at Each Constituent Layer of the Clad Composite during AWJM

The development of layered/clad composites with a blend of desired characteristics has emerged as a valuable substitute for expensive materials. The inherent heterogeneity offers challenges whenever the cutting of cladded plates/sheets is to be done. The conventional means of cutting such as gas/plasma arc yield a poor cut quality and heat-affected zones. Abrasive waterjet machining (AWJM) is a valuable alternative to mitigate the aforesaid cutting issues. However, the intrinsic attribute of edge damage during AWJM poses a limitation on its use, especially for precision applications. Specifically, it is challenging to control the edge damage in terms of pit depth at both the constituent clad layers and addressing this challenge is the novelty of this work. The said cutting accuracy issues have been thoroughly investigated herein. Four key control parameters of AWJM have been selected for evaluating their impact during machining of stainless-clad steel using L18 Taguchi design. Experimental results have been thoroughly examined using statistical and microscopical evidence. The optimal parametric combination resulting in the minimum magnitude of pit depth at both the clad layers has been developed and experimentally validated. The magnitude of pits depth realized at stainless steel layer (SSL) and mild steel layer (MSL) significantly reduced to 5 µm and 4 µm respectively, at the optimal parametric combination.