Search Results for shear extrusion

The next generation of materials and assemblies designed to address challenges in power generation, such as molten salt or supercritical carbon dioxide thermal transfer systems, corrosion, creep/fatigue, and higher temperature operation, will likely be highly optimized for their specific performance requirements. This optimization often involves strict control over microstructure, including homogeneity, grain size, texture, and grain boundary phases, as well as precise alloy chemistry and homogeneity. These stringent requirements aim to meet the new demands for bulk mechanical performance and durability. Some advanced materials, like oxide-dispersion strengthened or high-entropy alloys, necessitate specialized synthesis, fabrication, or welding/joining processes. Traditional methods that involve melting and solidifying can compromise the optimized microstructure of these materials, making non-melting synthesis and fabrication methods preferable to preserve their advanced characteristics. This paper presents examples where solid-phase, high-shear processing has produced materials and semi-finished products with superior performance compared to those made using conventional methods. While traditional processing often relies on thermodynamics-driven processes, such as creating precipitate phases through prolonged heat treatment, high-shear processing offers kinetics-driven, non-equilibrium alternatives that can yield high-performance microstructures. Additionally, examples are provided that demonstrate the potential for more cost-effective manufacturing routes due to fewer steps or lower energy requirements. This paper highlights advances in high-shear extrusion processing, including friction extrusion and shear-assisted processing and extrusion, as well as developments in solid-phase welding techniques like friction stir welding for next-generation power plant materials.

The manufacture of large, complex components for ultra-supercritical and oxy-combustion applications will be extremely costly for industry over the next few decades as many of these components will be manufactured from expensive, high strength, nickel-based alloys casting and forgings. The current feasibility study investigates the use of an alternative manufacturing method, powder metallurgy and hot isostatic processing (PM/HIP), to produce high quality, and potentially less expensive components for power generation applications. Benefits of the process include manufacture of components to near-net shapes, precise chemistry control, a homogeneous microstructure, increased material utilization, good weldability, and improved inspectability.

Advanced power systems that operate at temperatures higher than about 650°C will require nickel-base alloys in critical areas for pressure containment. Age-hardened alloys offer an additional advantage of reduced volume of material compared with lower strength solid solution-strengthened alloys if thinner tube wall can be specified. To date, the only age-hardened alloy that has been approved for service in the time dependent temperature regime in the ASME Boiler and Pressure Vessel Code is INCONEL alloy 740H. Extensive evaluation of seamless tube, pipe, and forged fittings in welded construction, including implant test loops and pilot plants, has shown the alloy to be fit for service in the 650-800°C (1202-1472°F) temperature range. Since, nickel-base alloys are much more expensive than steel, manufacturing methods that reduce the cost of material for advanced power plants are of great interest. One process that has been extensively used for stainless steels and solution-strengthened nickel-base alloys is continuous seam welding. This process has rarely been applied to age-hardened alloys and never for use as tube in the creep-limited temperature regime. This paper presents the initial results of a study to develop alloy 740H welded tube, pipe and fittings and to generate data to support establishment of ASME code maximum stress allowables.