Solid-State Welding of the Nanostructured Ferritic Alloy 14YWT Using a Capacitive Discharge Resistance Welding Technique

Joining nanostructured ferritic alloys (NFAs) has proved challenging, as the nano-oxides that provide superior strength, creep resistance, and radiation tolerance at high temperatures tend to agglomerate, redistribute, and coarsen during conventional fusion welding. In this study, capacitive discharge resistance welding (CDRW)—a solid-state variant of resistance welding—was used to join end caps and thin-walled cladding tubes of the NFA 14YWT. The resulting solid-state joints were found to be hermetically sealed and were characterized across the weld region using electron microscopy (macroscopic, microscopic, and nanometer scales) and nanoindentation. Microstructural evolution near the weld line was limited to narrow (~50–200 μm) thermo-mechanically affected zones (TMAZs) and to a reduction in pre-existing component textures. Dispersoid populations (i.e., nano-oxides and larger oxide particles) appeared unchanged by all but the highest energy and power CDRW condition, with this extreme producing only minor nano-oxide coarsening (~2 nm → ~5 nm Ø). Despite a minimal microstructural change, the TMAZs were found to be ~10% softer than the surrounding base material. These findings are considered in terms of past solid-state welding (SSW) efforts—cladding applications and NFA-like materials in particular—and in terms of strengthening mechanisms in NFAs and the potential impacts of localized temperature–strain conditions during SSW.

Study of the welded joint of VT1-0 titanium with 1.3343 steel

The work describes a method for obtaining a composite structure of small plates. The resulting plates are a layered structure consisting of a substrate (1.3343 steel) and a titanium coating (VT1-0). A method of resistance welding in the open air was applied to form a layered structure. The resulting titanium-steel compound was tensile tested. The maximum force at break of the welded joint varied in the range from 1.05 to 2.17 kN.

Characterization of a PCB Based Pressure Sensor and Its Joining Methods for the Metal Membrane

Essential quality features of pressure sensors are, among other accuracy-related factors, measurement range, operating temperature, and long-term stability. In this work, these features are optimized for a capacitive pressure sensor with a measurement range of 10 bars. The sensor consists of a metal membrane, which is connected to a PCB and a digital capacitive readout. To optimize the performance, different methods for the joining process are studied. Transient liquid phase bonding (TLP bonding), reactive joining, silver sintering, and electric resistance welding are compared by measurements of the characteristic curves and long-term measurements at maximum pressure. A scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) analysis was used to examine the quality of the joints. The evaluation of the characteristic curves shows the smallest measurement errors for TLP bonding and sintering. For welding and sintering, no statistically significant long-term drift was measured. In terms of equipment costs, reactive joining and sintering are most favorable. With low material costs and short process times, electric resistance welding offers ideal conditions for mass production.

Hybrid Welding of Metal-Polymer Composites with a Non- Conducting Polymer Layer

Metal-polymer composites (MPCs) are becoming increasingly popular primarily because of their high strength-to-weight ratio. Metal-polymer composites consist of three layers, i.e. two external metallic sheets (linings) and the core made of plastic. The presence of the internal plastic layer makes MPCs impossible to join using conventional welding processes, which significantly limits their usability. One of the solutions to the problem involves the use of hybrid methods, e.g. ultrasonic method-aided resistance welding. The research work discussed in the article involved the development of a prototype test rig and a technology enabling the joining of the Litecor® composite with steel DP600. The joining process consisted of two stages. The first stage involved the removal of the non-conducting layer of polymer from the welding area and the making of an appropriate electric contact for resistance welding. The second stage was the classical resistance spot welding process. The development of the concept posed a challenge as it was necessary to develop an appropriate acoustic waveguide for high-power ultrasonic waves which, at the same time, could transfer loads in the form of electrode force as well as provide appropriate electric and thermal conductivity without compromising acoustic parameters during the welding process. The development of the test rig was followed by the performance of numerous tests aimed to identify the appropriate window of process parameters. Test joints were subjected to macrographic, strength, ultrasonic and topographic tests.